annotate ffmpeg/doc/ffmpeg-filters.pod @ 13:844d341cf643 tip

Back up before ISMIR

=head1 NAME

ffmpeg-filters - FFmpeg filters

=head1 DESCRIPTION


This document describes filters, sources, and sinks provided by the
libavfilter library.



=head1 FILTERING INTRODUCTION


Filtering in FFmpeg is enabled through the libavfilter library.

In libavfilter, a filter can have multiple inputs and multiple
outputs.
To illustrate the sorts of things that are possible, we consider the
following filtergraph.

	
	input --> split ---------------------> overlay --> output
	            |                             ^
	            |                             |
	            +-----> crop --> vflip -------+


This filtergraph splits the input stream in two streams, sends one
stream through the crop filter and the vflip filter before merging it
back with the other stream by overlaying it on top. You can use the
following command to achieve this:

	
	ffmpeg -i INPUT -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" OUTPUT


The result will be that in output the top half of the video is mirrored
onto the bottom half.

Filters in the same linear chain are separated by commas, and distinct
linear chains of filters are separated by semicolons. In our example,
I<crop,vflip> are in one linear chain, I<split> and
I<overlay> are separately in another. The points where the linear
chains join are labelled by names enclosed in square brackets. In the
example, the split filter generates two outputs that are associated to
the labels I<[main]> and I<[tmp]>.

The stream sent to the second output of I<split>, labelled as
I<[tmp]>, is processed through the I<crop> filter, which crops
away the lower half part of the video, and then vertically flipped. The
I<overlay> filter takes in input the first unchanged output of the
split filter (which was labelled as I<[main]>), and overlay on its
lower half the output generated by the I<crop,vflip> filterchain.

Some filters take in input a list of parameters: they are specified
after the filter name and an equal sign, and are separated from each other
by a colon.

There exist so-called I<source filters> that do not have an
audio/video input, and I<sink filters> that will not have audio/video
output.



=head1 GRAPH


The F<graph2dot> program included in the FFmpeg F<tools>
directory can be used to parse a filtergraph description and issue a
corresponding textual representation in the dot language.

Invoke the command:
	
	graph2dot -h


to see how to use F<graph2dot>.

You can then pass the dot description to the F<dot> program (from
the graphviz suite of programs) and obtain a graphical representation
of the filtergraph.

For example the sequence of commands:
	
	echo <GRAPH_DESCRIPTION> | \
	tools/graph2dot -o graph.tmp && \
	dot -Tpng graph.tmp -o graph.png && \
	display graph.png


can be used to create and display an image representing the graph
described by the I<GRAPH_DESCRIPTION> string. Note that this string must be
a complete self-contained graph, with its inputs and outputs explicitly defined.
For example if your command line is of the form:
	
	ffmpeg -i infile -vf scale=640:360 outfile

your I<GRAPH_DESCRIPTION> string will need to be of the form:
	
	nullsrc,scale=640:360,nullsink

you may also need to set the I<nullsrc> parameters and add a I<format>
filter in order to simulate a specific input file.



=head1 FILTERGRAPH DESCRIPTION


A filtergraph is a directed graph of connected filters. It can contain
cycles, and there can be multiple links between a pair of
filters. Each link has one input pad on one side connecting it to one
filter from which it takes its input, and one output pad on the other
side connecting it to the one filter accepting its output.

Each filter in a filtergraph is an instance of a filter class
registered in the application, which defines the features and the
number of input and output pads of the filter.

A filter with no input pads is called a "source", a filter with no
output pads is called a "sink".



=head2 Filtergraph syntax


A filtergraph can be represented using a textual representation, which is
recognized by the B<-filter>/B<-vf> and B<-filter_complex>
options in B<ffmpeg> and B<-vf> in B<ffplay>, and by the
C<avfilter_graph_parse()>/C<avfilter_graph_parse2()> function defined in
F<libavfilter/avfilter.h>.

A filterchain consists of a sequence of connected filters, each one
connected to the previous one in the sequence. A filterchain is
represented by a list of ","-separated filter descriptions.

A filtergraph consists of a sequence of filterchains. A sequence of
filterchains is represented by a list of ";"-separated filterchain
descriptions.

A filter is represented by a string of the form:
[I<in_link_1>]...[I<in_link_N>]I<filter_name>=I<arguments>[I<out_link_1>]...[I<out_link_M>]

I<filter_name> is the name of the filter class of which the
described filter is an instance of, and has to be the name of one of
the filter classes registered in the program.
The name of the filter class is optionally followed by a string
"=I<arguments>".

I<arguments> is a string which contains the parameters used to
initialize the filter instance. It may have one of the following forms:

=over 4



=item *

A ':'-separated list of I<key=value> pairs.


=item *

A ':'-separated list of I<value>. In this case, the keys are assumed to be
the option names in the order they are declared. E.g. the C<fade> filter
declares three options in this order -- B<type>, B<start_frame> and
B<nb_frames>. Then the parameter list I<in:0:30> means that the value
I<in> is assigned to the option B<type>, I<0> to
B<start_frame> and I<30> to B<nb_frames>.


=item *

A ':'-separated list of mixed direct I<value> and long I<key=value>
pairs. The direct I<value> must precede the I<key=value> pairs, and
follow the same constraints order of the previous point. The following
I<key=value> pairs can be set in any preferred order.


=back


If the option value itself is a list of items (e.g. the C<format> filter
takes a list of pixel formats), the items in the list are usually separated by
'|'.

The list of arguments can be quoted using the character "'" as initial
and ending mark, and the character '\' for escaping the characters
within the quoted text; otherwise the argument string is considered
terminated when the next special character (belonging to the set
"[]=;,") is encountered.

The name and arguments of the filter are optionally preceded and
followed by a list of link labels.
A link label allows to name a link and associate it to a filter output
or input pad. The preceding labels I<in_link_1>
... I<in_link_N>, are associated to the filter input pads,
the following labels I<out_link_1> ... I<out_link_M>, are
associated to the output pads.

When two link labels with the same name are found in the
filtergraph, a link between the corresponding input and output pad is
created.

If an output pad is not labelled, it is linked by default to the first
unlabelled input pad of the next filter in the filterchain.
For example in the filterchain:
	
	nullsrc, split[L1], [L2]overlay, nullsink

the split filter instance has two output pads, and the overlay filter
instance two input pads. The first output pad of split is labelled
"L1", the first input pad of overlay is labelled "L2", and the second
output pad of split is linked to the second input pad of overlay,
which are both unlabelled.

In a complete filterchain all the unlabelled filter input and output
pads must be connected. A filtergraph is considered valid if all the
filter input and output pads of all the filterchains are connected.

Libavfilter will automatically insert scale filters where format
conversion is required. It is possible to specify swscale flags
for those automatically inserted scalers by prepending
C<sws_flags=I<flags>;>
to the filtergraph description.

Follows a BNF description for the filtergraph syntax:
	
	<NAME>             ::= sequence of alphanumeric characters and '_'
	<LINKLABEL>        ::= "[" <NAME> "]"
	<LINKLABELS>       ::= <LINKLABEL> [<LINKLABELS>]
	<FILTER_ARGUMENTS> ::= sequence of chars (eventually quoted)
	<FILTER>           ::= [<LINKLABELS>] <NAME> ["=" <FILTER_ARGUMENTS>] [<LINKLABELS>]
	<FILTERCHAIN>      ::= <FILTER> [,<FILTERCHAIN>]
	<FILTERGRAPH>      ::= [sws_flags=<flags>;] <FILTERCHAIN> [;<FILTERGRAPH>]



=head2 Notes on filtergraph escaping


Some filter arguments require the use of special characters, typically
C<:> to separate key=value pairs in a named options list. In this
case the user should perform a first level escaping when specifying
the filter arguments. For example, consider the following literal
string to be embedded in the drawtext filter arguments:
	
	this is a 'string': may contain one, or more, special characters


Since C<:> is special for the filter arguments syntax, it needs to
be escaped, so you get:
	
	text=this is a \'string\'\: may contain one, or more, special characters


A second level of escaping is required when embedding the filter
arguments in a filtergraph description, in order to escape all the
filtergraph special characters. Thus the example above becomes:
	
	drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters


Finally an additional level of escaping may be needed when writing the
filtergraph description in a shell command, which depends on the
escaping rules of the adopted shell. For example, assuming that
C<\> is special and needs to be escaped with another C<\>, the
previous string will finally result in:
	
	-vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"


Sometimes, it might be more convenient to employ quoting in place of
escaping. For example the string:
	
	Caesar: tu quoque, Brute, fili mi


Can be quoted in the filter arguments as:
	
	text='Caesar: tu quoque, Brute, fili mi'


And finally inserted in a filtergraph like:
	
	drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'


See the ``Quoting and escaping'' section in the ffmpeg-utils manual
for more information about the escaping and quoting rules adopted by
FFmpeg.



=head1 AUDIO FILTERS


When you configure your FFmpeg build, you can disable any of the
existing filters using C<--disable-filters>.
The configure output will show the audio filters included in your
build.

Below is a description of the currently available audio filters.


=head2 aconvert


Convert the input audio format to the specified formats.

I<This filter is deprecated. Use aformat> instead.

The filter accepts a string of the form:
"I<sample_format>:I<channel_layout>".

I<sample_format> specifies the sample format, and can be a string or the
corresponding numeric value defined in F<libavutil/samplefmt.h>. Use 'p'
suffix for a planar sample format.

I<channel_layout> specifies the channel layout, and can be a string
or the corresponding number value defined in F<libavutil/channel_layout.h>.

The special parameter "auto", signifies that the filter will
automatically select the output format depending on the output filter.


=head3 Examples



=over 4


=item *

Convert input to float, planar, stereo:
	
	aconvert=fltp:stereo



=item *

Convert input to unsigned 8-bit, automatically select out channel layout:
	
	aconvert=u8:auto


=back



=head2 allpass


Apply a two-pole all-pass filter with central frequency (in Hz)
I<frequency>, and filter-width I<width>.
An all-pass filter changes the audio's frequency to phase relationship
without changing its frequency to amplitude relationship.

The filter accepts the following options:


=over 4


=item B<frequency, f>

Set frequency in Hz.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Specify the band-width of a filter in width_type units.

=back



=head2 highpass


Apply a high-pass filter with 3dB point frequency.
The filter can be either single-pole, or double-pole (the default).
The filter roll off at 6dB per pole per octave (20dB per pole per decade).

The filter accepts the following options:


=over 4


=item B<frequency, f>

Set frequency in Hz. Default is 3000.


=item B<poles, p>

Set number of poles. Default is 2.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Specify the band-width of a filter in width_type units.
Applies only to double-pole filter.
The default is 0.707q and gives a Butterworth response.

=back



=head2 lowpass


Apply a low-pass filter with 3dB point frequency.
The filter can be either single-pole or double-pole (the default).
The filter roll off at 6dB per pole per octave (20dB per pole per decade).

The filter accepts the following options:


=over 4


=item B<frequency, f>

Set frequency in Hz. Default is 500.


=item B<poles, p>

Set number of poles. Default is 2.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Specify the band-width of a filter in width_type units.
Applies only to double-pole filter.
The default is 0.707q and gives a Butterworth response.

=back



=head2 bass


Boost or cut the bass (lower) frequencies of the audio using a two-pole
shelving filter with a response similar to that of a standard
hi-fi's tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:


=over 4


=item B<gain, g>

Give the gain at 0 Hz. Its useful range is about -20
(for a large cut) to +20 (for a large boost).
Beware of clipping when using a positive gain.


=item B<frequency, f>

Set the filter's central frequency and so can be used
to extend or reduce the frequency range to be boosted or cut.
The default value is C<100> Hz.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Determine how steep is the filter's shelf transition.

=back



=head2 treble


Boost or cut treble (upper) frequencies of the audio using a two-pole
shelving filter with a response similar to that of a standard
hi-fi's tone-controls. This is also known as shelving equalisation (EQ).

The filter accepts the following options:


=over 4


=item B<gain, g>

Give the gain at whichever is the lower of ~22 kHz and the
Nyquist frequency. Its useful range is about -20 (for a large cut)
to +20 (for a large boost). Beware of clipping when using a positive gain.


=item B<frequency, f>

Set the filter's central frequency and so can be used
to extend or reduce the frequency range to be boosted or cut.
The default value is C<3000> Hz.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Determine how steep is the filter's shelf transition.

=back



=head2 bandpass


Apply a two-pole Butterworth band-pass filter with central
frequency I<frequency>, and (3dB-point) band-width width.
The I<csg> option selects a constant skirt gain (peak gain = Q)
instead of the default: constant 0dB peak gain.
The filter roll off at 6dB per octave (20dB per decade).

The filter accepts the following options:


=over 4


=item B<frequency, f>

Set the filter's central frequency. Default is C<3000>.


=item B<csg>

Constant skirt gain if set to 1. Defaults to 0.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Specify the band-width of a filter in width_type units.

=back



=head2 bandreject


Apply a two-pole Butterworth band-reject filter with central
frequency I<frequency>, and (3dB-point) band-width I<width>.
The filter roll off at 6dB per octave (20dB per decade).

The filter accepts the following options:


=over 4


=item B<frequency, f>

Set the filter's central frequency. Default is C<3000>.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Specify the band-width of a filter in width_type units.

=back



=head2 biquad


Apply a biquad IIR filter with the given coefficients.
Where I<b0>, I<b1>, I<b2> and I<a0>, I<a1>, I<a2>
are the numerator and denominator coefficients respectively.


=head2 equalizer


Apply a two-pole peaking equalisation (EQ) filter. With this
filter, the signal-level at and around a selected frequency can
be increased or decreased, whilst (unlike bandpass and bandreject
filters) that at all other frequencies is unchanged.

In order to produce complex equalisation curves, this filter can
be given several times, each with a different central frequency.

The filter accepts the following options:


=over 4


=item B<frequency, f>

Set the filter's central frequency in Hz.


=item B<width_type>

Set method to specify band-width of filter.

=over 4


=item B<h>

Hz

=item B<q>

Q-Factor

=item B<o>

octave

=item B<s>

slope

=back



=item B<width, w>

Specify the band-width of a filter in width_type units.


=item B<gain, g>

Set the required gain or attenuation in dB.
Beware of clipping when using a positive gain.

=back



=head2 afade


Apply fade-in/out effect to input audio.

A description of the accepted parameters follows.


=over 4


=item B<type, t>

Specify the effect type, can be either C<in> for fade-in, or
C<out> for a fade-out effect. Default is C<in>.


=item B<start_sample, ss>

Specify the number of the start sample for starting to apply the fade
effect. Default is 0.


=item B<nb_samples, ns>

Specify the number of samples for which the fade effect has to last. At
the end of the fade-in effect the output audio will have the same
volume as the input audio, at the end of the fade-out transition
the output audio will be silence. Default is 44100.


=item B<start_time, st>

Specify time for starting to apply the fade effect. Default is 0.
The accepted syntax is:
	
	[-]HH[:MM[:SS[.m...]]]
	[-]S+[.m...]

See also the function C<av_parse_time()>.
If set this option is used instead of I<start_sample> one.


=item B<duration, d>

Specify the duration for which the fade effect has to last. Default is 0.
The accepted syntax is:
	
	[-]HH[:MM[:SS[.m...]]]
	[-]S+[.m...]

See also the function C<av_parse_time()>.
At the end of the fade-in effect the output audio will have the same
volume as the input audio, at the end of the fade-out transition
the output audio will be silence.
If set this option is used instead of I<nb_samples> one.


=item B<curve>

Set curve for fade transition.

It accepts the following values:

=over 4


=item B<tri>

select triangular, linear slope (default)

=item B<qsin>

select quarter of sine wave

=item B<hsin>

select half of sine wave

=item B<esin>

select exponential sine wave

=item B<log>

select logarithmic

=item B<par>

select inverted parabola

=item B<qua>

select quadratic

=item B<cub>

select cubic

=item B<squ>

select square root

=item B<cbr>

select cubic root

=back


=back



=head3 Examples



=over 4


=item *

Fade in first 15 seconds of audio:
	
	afade=t=in:ss=0:d=15



=item *

Fade out last 25 seconds of a 900 seconds audio:
	
	afade=t=out:ss=875:d=25


=back




=head2 aformat


Set output format constraints for the input audio. The framework will
negotiate the most appropriate format to minimize conversions.

The filter accepts the following named parameters:

=over 4



=item B<sample_fmts>

A '|'-separated list of requested sample formats.


=item B<sample_rates>

A '|'-separated list of requested sample rates.


=item B<channel_layouts>

A '|'-separated list of requested channel layouts.


=back


If a parameter is omitted, all values are allowed.

For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
	
	aformat=sample_fmts=u8|s16:channel_layouts=stereo



=head2 amerge


Merge two or more audio streams into a single multi-channel stream.

The filter accepts the following options:


=over 4



=item B<inputs>

Set the number of inputs. Default is 2.


=back


If the channel layouts of the inputs are disjoint, and therefore compatible,
the channel layout of the output will be set accordingly and the channels
will be reordered as necessary. If the channel layouts of the inputs are not
disjoint, the output will have all the channels of the first input then all
the channels of the second input, in that order, and the channel layout of
the output will be the default value corresponding to the total number of
channels.

For example, if the first input is in 2.1 (FL+FR+LF) and the second input
is FC+BL+BR, then the output will be in 5.1, with the channels in the
following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
first input, b1 is the first channel of the second input).

On the other hand, if both input are in stereo, the output channels will be
in the default order: a1, a2, b1, b2, and the channel layout will be
arbitrarily set to 4.0, which may or may not be the expected value.

All inputs must have the same sample rate, and format.

If inputs do not have the same duration, the output will stop with the
shortest.


=head3 Examples



=over 4


=item *

Merge two mono files into a stereo stream:
	
	amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge



=item *

Multiple merges assuming 1 video stream and 6 audio streams in F<input.mkv>:
	
	ffmpeg -i input.mkv -filter_complex "[0:1][0:2][0:3][0:4][0:5][0:6] amerge=inputs=6" -c:a pcm_s16le output.mkv


=back



=head2 amix


Mixes multiple audio inputs into a single output.

For example
	
	ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT

will mix 3 input audio streams to a single output with the same duration as the
first input and a dropout transition time of 3 seconds.

The filter accepts the following named parameters:

=over 4



=item B<inputs>

Number of inputs. If unspecified, it defaults to 2.


=item B<duration>

How to determine the end-of-stream.

=over 4



=item B<longest>

Duration of longest input. (default)


=item B<shortest>

Duration of shortest input.


=item B<first>

Duration of first input.


=back



=item B<dropout_transition>

Transition time, in seconds, for volume renormalization when an input
stream ends. The default value is 2 seconds.


=back



=head2 anull


Pass the audio source unchanged to the output.


=head2 apad


Pad the end of a audio stream with silence, this can be used together with
-shortest to extend audio streams to the same length as the video stream.


=head2 aphaser

Add a phasing effect to the input audio.

A phaser filter creates series of peaks and troughs in the frequency spectrum.
The position of the peaks and troughs are modulated so that they vary over time, creating a sweeping effect.

A description of the accepted parameters follows.


=over 4


=item B<in_gain>

Set input gain. Default is 0.4.


=item B<out_gain>

Set output gain. Default is 0.74


=item B<delay>

Set delay in milliseconds. Default is 3.0.


=item B<decay>

Set decay. Default is 0.4.


=item B<speed>

Set modulation speed in Hz. Default is 0.5.


=item B<type>

Set modulation type. Default is triangular.

It accepts the following values:

=over 4


=item B<triangular, t>


=item B<sinusoidal, s>


=back


=back




=head2 aresample


Resample the input audio to the specified parameters, using the
libswresample library. If none are specified then the filter will
automatically convert between its input and output.

This filter is also able to stretch/squeeze the audio data to make it match
the timestamps or to inject silence / cut out audio to make it match the
timestamps, do a combination of both or do neither.

The filter accepts the syntax
[I<sample_rate>:]I<resampler_options>, where I<sample_rate>
expresses a sample rate and I<resampler_options> is a list of
I<key>=I<value> pairs, separated by ":". See the
ffmpeg-resampler manual for the complete list of supported options.


=head3 Examples



=over 4


=item *

Resample the input audio to 44100Hz:
	
	aresample=44100



=item *

Stretch/squeeze samples to the given timestamps, with a maximum of 1000
samples per second compensation:
	
	aresample=async=1000


=back



=head2 asetnsamples


Set the number of samples per each output audio frame.

The last output packet may contain a different number of samples, as
the filter will flush all the remaining samples when the input audio
signal its end.

The filter accepts the following options:


=over 4



=item B<nb_out_samples, n>

Set the number of frames per each output audio frame. The number is
intended as the number of samples I<per each channel>.
Default value is 1024.


=item B<pad, p>

If set to 1, the filter will pad the last audio frame with zeroes, so
that the last frame will contain the same number of samples as the
previous ones. Default value is 1.

=back


For example, to set the number of per-frame samples to 1234 and
disable padding for the last frame, use:
	
	asetnsamples=n=1234:p=0



=head2 ashowinfo


Show a line containing various information for each input audio frame.
The input audio is not modified.

The shown line contains a sequence of key/value pairs of the form
I<key>:I<value>.

A description of each shown parameter follows:


=over 4


=item B<n>

sequential number of the input frame, starting from 0


=item B<pts>

Presentation timestamp of the input frame, in time base units; the time base
depends on the filter input pad, and is usually 1/I<sample_rate>.


=item B<pts_time>

presentation timestamp of the input frame in seconds


=item B<pos>

position of the frame in the input stream, -1 if this information in
unavailable and/or meaningless (for example in case of synthetic audio)


=item B<fmt>

sample format


=item B<chlayout>

channel layout


=item B<rate>

sample rate for the audio frame


=item B<nb_samples>

number of samples (per channel) in the frame


=item B<checksum>

Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
the data is treated as if all the planes were concatenated.


=item B<plane_checksums>

A list of Adler-32 checksums for each data plane.

=back



=head2 astreamsync


Forward two audio streams and control the order the buffers are forwarded.

The filter accepts the following options:


=over 4


=item B<expr, e>

Set the expression deciding which stream should be
forwarded next: if the result is negative, the first stream is forwarded; if
the result is positive or zero, the second stream is forwarded. It can use
the following variables:


=over 4


=item I<b1 b2>

number of buffers forwarded so far on each stream

=item I<s1 s2>

number of samples forwarded so far on each stream

=item I<t1 t2>

current timestamp of each stream

=back


The default value is C<t1-t2>, which means to always forward the stream
that has a smaller timestamp.

=back



=head3 Examples


Stress-test C<amerge> by randomly sending buffers on the wrong
input, while avoiding too much of a desynchronization:
	
	amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
	[a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
	[a2] [b2] amerge



=head2 atempo


Adjust audio tempo.

The filter accepts exactly one parameter, the audio tempo. If not
specified then the filter will assume nominal 1.0 tempo. Tempo must
be in the [0.5, 2.0] range.


=head3 Examples



=over 4


=item *

Slow down audio to 80% tempo:
	
	atempo=0.8



=item *

To speed up audio to 125% tempo:
	
	atempo=1.25


=back



=head2 earwax


Make audio easier to listen to on headphones.

This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
so that when listened to on headphones the stereo image is moved from
inside your head (standard for headphones) to outside and in front of
the listener (standard for speakers).

Ported from SoX.


=head2 pan


Mix channels with specific gain levels. The filter accepts the output
channel layout followed by a set of channels definitions.

This filter is also designed to remap efficiently the channels of an audio
stream.

The filter accepts parameters of the form:
"I<l>:I<outdef>:I<outdef>:..."


=over 4


=item B<l>

output channel layout or number of channels


=item B<outdef>

output channel specification, of the form:
"I<out_name>=[I<gain>*]I<in_name>[+[I<gain>*]I<in_name>...]"


=item B<out_name>

output channel to define, either a channel name (FL, FR, etc.) or a channel
number (c0, c1, etc.)


=item B<gain>

multiplicative coefficient for the channel, 1 leaving the volume unchanged


=item B<in_name>

input channel to use, see out_name for details; it is not possible to mix
named and numbered input channels

=back


If the `=' in a channel specification is replaced by `E<lt>', then the gains for
that specification will be renormalized so that the total is 1, thus
avoiding clipping noise.


=head3 Mixing examples


For example, if you want to down-mix from stereo to mono, but with a bigger
factor for the left channel:
	
	pan=1:c0=0.9*c0+0.1*c1


A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
7-channels surround:
	
	pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR


Note that B<ffmpeg> integrates a default down-mix (and up-mix) system
that should be preferred (see "-ac" option) unless you have very specific
needs.


=head3 Remapping examples


The channel remapping will be effective if, and only if:


=over 4


=item *<gain coefficients are zeroes or ones,>


=item *<only one input per channel output,>


=back


If all these conditions are satisfied, the filter will notify the user ("Pure
channel mapping detected"), and use an optimized and lossless method to do the
remapping.

For example, if you have a 5.1 source and want a stereo audio stream by
dropping the extra channels:
	
	pan="stereo: c0=FL : c1=FR"


Given the same source, you can also switch front left and front right channels
and keep the input channel layout:
	
	pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"


If the input is a stereo audio stream, you can mute the front left channel (and
still keep the stereo channel layout) with:
	
	pan="stereo:c1=c1"


Still with a stereo audio stream input, you can copy the right channel in both
front left and right:
	
	pan="stereo: c0=FR : c1=FR"



=head2 silencedetect


Detect silence in an audio stream.

This filter logs a message when it detects that the input audio volume is less
or equal to a noise tolerance value for a duration greater or equal to the
minimum detected noise duration.

The printed times and duration are expressed in seconds.

The filter accepts the following options:


=over 4


=item B<duration, d>

Set silence duration until notification (default is 2 seconds).


=item B<noise, n>

Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
specified value) or amplitude ratio. Default is -60dB, or 0.001.

=back



=head3 Examples



=over 4


=item *

Detect 5 seconds of silence with -50dB noise tolerance:
	
	silencedetect=n=-50dB:d=5



=item *

Complete example with B<ffmpeg> to detect silence with 0.0001 noise
tolerance in F<silence.mp3>:
	
	ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -


=back



=head2 asyncts

Synchronize audio data with timestamps by squeezing/stretching it and/or
dropping samples/adding silence when needed.

This filter is not built by default, please use aresample to do squeezing/stretching.

The filter accepts the following named parameters:

=over 4



=item B<compensate>

Enable stretching/squeezing the data to make it match the timestamps. Disabled
by default. When disabled, time gaps are covered with silence.


=item B<min_delta>

Minimum difference between timestamps and audio data (in seconds) to trigger
adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
this filter, try setting this parameter to 0.


=item B<max_comp>

Maximum compensation in samples per second. Relevant only with compensate=1.
Default value 500.


=item B<first_pts>

Assume the first pts should be this value. The time base is 1 / sample rate.
This allows for padding/trimming at the start of stream. By default, no
assumption is made about the first frame's expected pts, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
silence if an audio stream starts after the video stream or to trim any samples
with a negative pts due to encoder delay.


=back



=head2 channelsplit

Split each channel in input audio stream into a separate output stream.

This filter accepts the following named parameters:

=over 4


=item B<channel_layout>

Channel layout of the input stream. Default is "stereo".

=back


For example, assuming a stereo input MP3 file
	
	ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv

will create an output Matroska file with two audio streams, one containing only
the left channel and the other the right channel.

To split a 5.1 WAV file into per-channel files
	
	ffmpeg -i in.wav -filter_complex
	'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
	-map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
	front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
	side_right.wav



=head2 channelmap

Remap input channels to new locations.

This filter accepts the following named parameters:

=over 4


=item B<channel_layout>

Channel layout of the output stream.


=item B<map>

Map channels from input to output. The argument is a '|'-separated list of
mappings, each in the C<I<in_channel>-I<out_channel>> or
I<in_channel> form. I<in_channel> can be either the name of the input
channel (e.g. FL for front left) or its index in the input channel layout.
I<out_channel> is the name of the output channel or its index in the output
channel layout. If I<out_channel> is not given then it is implicitly an
index, starting with zero and increasing by one for each mapping.

=back


If no mapping is present, the filter will implicitly map input channels to
output channels preserving index.

For example, assuming a 5.1+downmix input MOV file
	
	ffmpeg -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav

will create an output WAV file tagged as stereo from the downmix channels of
the input.

To fix a 5.1 WAV improperly encoded in AAC's native channel order
	
	ffmpeg -i in.wav -filter 'channelmap=1|2|0|5|3|4:channel_layout=5.1' out.wav



=head2 join

Join multiple input streams into one multi-channel stream.

The filter accepts the following named parameters:

=over 4



=item B<inputs>

Number of input streams. Defaults to 2.


=item B<channel_layout>

Desired output channel layout. Defaults to stereo.


=item B<map>

Map channels from inputs to output. The argument is a '|'-separated list of
mappings, each in the C<I<input_idx>.I<in_channel>-I<out_channel>>
form. I<input_idx> is the 0-based index of the input stream. I<in_channel>
can be either the name of the input channel (e.g. FL for front left) or its
index in the specified input stream. I<out_channel> is the name of the output
channel.

=back


The filter will attempt to guess the mappings when those are not specified
explicitly. It does so by first trying to find an unused matching input channel
and if that fails it picks the first unused input channel.

E.g. to join 3 inputs (with properly set channel layouts)
	
	ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT


To build a 5.1 output from 6 single-channel streams:
	
	ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
	'join=inputs=6:channel_layout=5.1:map=0.0-FL|1.0-FR|2.0-FC|3.0-SL|4.0-SR|5.0-LFE'
	out



=head2 resample

Convert the audio sample format, sample rate and channel layout. This filter is
not meant to be used directly.


=head2 volume


Adjust the input audio volume.

The filter accepts the following options:


=over 4



=item B<volume>

Expresses how the audio volume will be increased or decreased.

Output values are clipped to the maximum value.

The output audio volume is given by the relation:
	
	<output_volume> = <volume> * <input_volume>


Default value for I<volume> is 1.0.


=item B<precision>

Set the mathematical precision.

This determines which input sample formats will be allowed, which affects the
precision of the volume scaling.


=over 4


=item B<fixed>

8-bit fixed-point; limits input sample format to U8, S16, and S32.

=item B<float>

32-bit floating-point; limits input sample format to FLT. (default)

=item B<double>

64-bit floating-point; limits input sample format to DBL.

=back


=back



=head3 Examples



=over 4


=item *

Halve the input audio volume:
	
	volume=volume=0.5
	volume=volume=1/2
	volume=volume=-6.0206dB


In all the above example the named key for B<volume> can be
omitted, for example like in:
	
	volume=0.5



=item *

Increase input audio power by 6 decibels using fixed-point precision:
	
	volume=volume=6dB:precision=fixed


=back



=head2 volumedetect


Detect the volume of the input video.

The filter has no parameters. The input is not modified. Statistics about
the volume will be printed in the log when the input stream end is reached.

In particular it will show the mean volume (root mean square), maximum
volume (on a per-sample basis), and the beginning of an histogram of the
registered volume values (from the maximum value to a cumulated 1/1000 of
the samples).

All volumes are in decibels relative to the maximum PCM value.


=head3 Examples


Here is an excerpt of the output:
	
	[Parsed_volumedetect_0  0xa23120] mean_volume: -27 dB
	[Parsed_volumedetect_0  0xa23120] max_volume: -4 dB
	[Parsed_volumedetect_0  0xa23120] histogram_4db: 6
	[Parsed_volumedetect_0  0xa23120] histogram_5db: 62
	[Parsed_volumedetect_0  0xa23120] histogram_6db: 286
	[Parsed_volumedetect_0  0xa23120] histogram_7db: 1042
	[Parsed_volumedetect_0  0xa23120] histogram_8db: 2551
	[Parsed_volumedetect_0  0xa23120] histogram_9db: 4609
	[Parsed_volumedetect_0  0xa23120] histogram_10db: 8409


It means that:

=over 4


=item *

The mean square energy is approximately -27 dB, or 10^-2.7.

=item *

The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.

=item *

There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.

=back


In other words, raising the volume by +4 dB does not cause any clipping,
raising it by +5 dB causes clipping for 6 samples, etc.



=head1 AUDIO SOURCES


Below is a description of the currently available audio sources.


=head2 abuffer


Buffer audio frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular
through the interface defined in F<libavfilter/asrc_abuffer.h>.

It accepts the following named parameters:


=over 4



=item B<time_base>

Timebase which will be used for timestamps of submitted frames. It must be
either a floating-point number or in I<numerator>/I<denominator> form.


=item B<sample_rate>

The sample rate of the incoming audio buffers.


=item B<sample_fmt>

The sample format of the incoming audio buffers.
Either a sample format name or its corresponging integer representation from
the enum AVSampleFormat in F<libavutil/samplefmt.h>


=item B<channel_layout>

The channel layout of the incoming audio buffers.
Either a channel layout name from channel_layout_map in
F<libavutil/channel_layout.c> or its corresponding integer representation
from the AV_CH_LAYOUT_* macros in F<libavutil/channel_layout.h>


=item B<channels>

The number of channels of the incoming audio buffers.
If both I<channels> and I<channel_layout> are specified, then they
must be consistent.


=back



=head3 Examples


	
	abuffer=sample_rate=44100:sample_fmt=s16p:channel_layout=stereo


will instruct the source to accept planar 16bit signed stereo at 44100Hz.
Since the sample format with name "s16p" corresponds to the number
6 and the "stereo" channel layout corresponds to the value 0x3, this is
equivalent to:
	
	abuffer=sample_rate=44100:sample_fmt=6:channel_layout=0x3



=head2 aevalsrc


Generate an audio signal specified by an expression.

This source accepts in input one or more expressions (one for each
channel), which are evaluated and used to generate a corresponding
audio signal.

This source accepts the following options:


=over 4


=item B<exprs>

Set the '|'-separated expressions list for each separate channel. In case the
B<channel_layout> option is not specified, the selected channel layout
depends on the number of provided expressions.


=item B<channel_layout, c>

Set the channel layout. The number of channels in the specified layout
must be equal to the number of specified expressions.


=item B<duration, d>

Set the minimum duration of the sourced audio. See the function
C<av_parse_time()> for the accepted format.
Note that the resulting duration may be greater than the specified
duration, as the generated audio is always cut at the end of a
complete frame.

If not specified, or the expressed duration is negative, the audio is
supposed to be generated forever.


=item B<nb_samples, n>

Set the number of samples per channel per each output frame,
default to 1024.


=item B<sample_rate, s>

Specify the sample rate, default to 44100.

=back


Each expression in I<exprs> can contain the following constants:


=over 4


=item B<n>

number of the evaluated sample, starting from 0


=item B<t>

time of the evaluated sample expressed in seconds, starting from 0


=item B<s>

sample rate


=back



=head3 Examples



=over 4


=item *

Generate silence:
	
	aevalsrc=0



=item *

Generate a sin signal with frequency of 440 Hz, set sample rate to
8000 Hz:
	
	aevalsrc="sin(440*2*PI*t):s=8000"



=item *

Generate a two channels signal, specify the channel layout (Front
Center + Back Center) explicitly:
	
	aevalsrc="sin(420*2*PI*t)|cos(430*2*PI*t):c=FC|BC"



=item *

Generate white noise:
	
	aevalsrc="-2+random(0)"



=item *

Generate an amplitude modulated signal:
	
	aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"



=item *

Generate 2.5 Hz binaural beats on a 360 Hz carrier:
	
	aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) | 0.1*sin(2*PI*(360+2.5/2)*t)"



=back



=head2 anullsrc


Null audio source, return unprocessed audio frames. It is mainly useful
as a template and to be employed in analysis / debugging tools, or as
the source for filters which ignore the input data (for example the sox
synth filter).

This source accepts the following options:


=over 4



=item B<channel_layout, cl>


Specify the channel layout, and can be either an integer or a string
representing a channel layout. The default value of I<channel_layout>
is "stereo".

Check the channel_layout_map definition in
F<libavutil/channel_layout.c> for the mapping between strings and
channel layout values.


=item B<sample_rate, r>

Specify the sample rate, and defaults to 44100.


=item B<nb_samples, n>

Set the number of samples per requested frames.


=back



=head3 Examples



=over 4


=item *

Set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
	
	anullsrc=r=48000:cl=4



=item *

Do the same operation with a more obvious syntax:
	
	anullsrc=r=48000:cl=mono


=back



=head2 abuffer

Buffer audio frames, and make them available to the filter chain.

This source is not intended to be part of user-supplied graph descriptions but
for insertion by calling programs through the interface defined in
F<libavfilter/buffersrc.h>.

It accepts the following named parameters:

=over 4



=item B<time_base>

Timebase which will be used for timestamps of submitted frames. It must be
either a floating-point number or in I<numerator>/I<denominator> form.


=item B<sample_rate>

Audio sample rate.


=item B<sample_fmt>

Name of the sample format, as returned by C<av_get_sample_fmt_name()>.


=item B<channel_layout>

Channel layout of the audio data, in the form that can be accepted by
C<av_get_channel_layout()>.

=back


All the parameters need to be explicitly defined.


=head2 flite


Synthesize a voice utterance using the libflite library.

To enable compilation of this filter you need to configure FFmpeg with
C<--enable-libflite>.

Note that the flite library is not thread-safe.

The filter accepts the following options:


=over 4



=item B<list_voices>

If set to 1, list the names of the available voices and exit
immediately. Default value is 0.


=item B<nb_samples, n>

Set the maximum number of samples per frame. Default value is 512.


=item B<textfile>

Set the filename containing the text to speak.


=item B<text>

Set the text to speak.


=item B<voice, v>

Set the voice to use for the speech synthesis. Default value is
C<kal>. See also the I<list_voices> option.

=back



=head3 Examples



=over 4


=item *

Read from file F<speech.txt>, and synthetize the text using the
standard flite voice:
	
	flite=textfile=speech.txt



=item *

Read the specified text selecting the C<slt> voice:
	
	flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt



=item *

Input text to ffmpeg:
	
	ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt



=item *

Make F<ffplay> speak the specified text, using C<flite> and
the C<lavfi> device:
	
	ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'


=back


For more information about libflite, check:
E<lt>B<http://www.speech.cs.cmu.edu/flite/>E<gt>


=head2 sine


Generate an audio signal made of a sine wave with amplitude 1/8.

The audio signal is bit-exact.

The filter accepts the following options:


=over 4



=item B<frequency, f>

Set the carrier frequency. Default is 440 Hz.


=item B<beep_factor, b>

Enable a periodic beep every second with frequency I<beep_factor> times
the carrier frequency. Default is 0, meaning the beep is disabled.


=item B<sample_rate, s>

Specify the sample rate, default is 44100.


=item B<duration, d>

Specify the duration of the generated audio stream.


=item B<samples_per_frame>

Set the number of samples per output frame, default is 1024.

=back



=head3 Examples



=over 4



=item *

Generate a simple 440 Hz sine wave:
	
	sine



=item *

Generate a 220 Hz sine wave with a 880 Hz beep each second, for 5 seconds:
	
	sine=220:4:d=5
	sine=f=220:b=4:d=5
	sine=frequency=220:beep_factor=4:duration=5



=back




=head1 AUDIO SINKS


Below is a description of the currently available audio sinks.


=head2 abuffersink


Buffer audio frames, and make them available to the end of filter chain.

This sink is mainly intended for programmatic use, in particular
through the interface defined in F<libavfilter/buffersink.h>
or the options system.

It accepts a pointer to an AVABufferSinkContext structure, which
defines the incoming buffers' formats, to be passed as the opaque
parameter to C<avfilter_init_filter> for initialization.


=head2 anullsink


Null audio sink, do absolutely nothing with the input audio. It is
mainly useful as a template and to be employed in analysis / debugging
tools.



=head1 VIDEO FILTERS


When you configure your FFmpeg build, you can disable any of the
existing filters using C<--disable-filters>.
The configure output will show the video filters included in your
build.

Below is a description of the currently available video filters.


=head2 alphaextract


Extract the alpha component from the input as a grayscale video. This
is especially useful with the I<alphamerge> filter.


=head2 alphamerge


Add or replace the alpha component of the primary input with the
grayscale value of a second input. This is intended for use with
I<alphaextract> to allow the transmission or storage of frame
sequences that have alpha in a format that doesn't support an alpha
channel.

For example, to reconstruct full frames from a normal YUV-encoded video
and a separate video created with I<alphaextract>, you might use:
	
	movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]


Since this filter is designed for reconstruction, it operates on frame
sequences without considering timestamps, and terminates when either
input reaches end of stream. This will cause problems if your encoding
pipeline drops frames. If you're trying to apply an image as an
overlay to a video stream, consider the I<overlay> filter instead.


=head2 ass


Same as the subtitles filter, except that it doesn't require libavcodec
and libavformat to work. On the other hand, it is limited to ASS (Advanced
Substation Alpha) subtitles files.


=head2 bbox


Compute the bounding box for the non-black pixels in the input frame
luminance plane.

This filter computes the bounding box containing all the pixels with a
luminance value greater than the minimum allowed value.
The parameters describing the bounding box are printed on the filter
log.


=head2 blackdetect


Detect video intervals that are (almost) completely black. Can be
useful to detect chapter transitions, commercials, or invalid
recordings. Output lines contains the time for the start, end and
duration of the detected black interval expressed in seconds.

In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.

The filter accepts the following options:


=over 4


=item B<black_min_duration, d>

Set the minimum detected black duration expressed in seconds. It must
be a non-negative floating point number.

Default value is 2.0.


=item B<picture_black_ratio_th, pic_th>

Set the threshold for considering a picture "black".
Express the minimum value for the ratio:
	
	<nb_black_pixels> / <nb_pixels>


for which a picture is considered black.
Default value is 0.98.


=item B<pixel_black_th, pix_th>

Set the threshold for considering a pixel "black".

The threshold expresses the maximum pixel luminance value for which a
pixel is considered "black". The provided value is scaled according to
the following equation:
	
	<absolute_threshold> = <luminance_minimum_value> + <pixel_black_th> * <luminance_range_size>


I<luminance_range_size> and I<luminance_minimum_value> depend on
the input video format, the range is [0-255] for YUV full-range
formats and [16-235] for YUV non full-range formats.

Default value is 0.10.

=back


The following example sets the maximum pixel threshold to the minimum
value, and detects only black intervals of 2 or more seconds:
	
	blackdetect=d=2:pix_th=0.00



=head2 blackframe


Detect frames that are (almost) completely black. Can be useful to
detect chapter transitions or commercials. Output lines consist of
the frame number of the detected frame, the percentage of blackness,
the position in the file if known or -1 and the timestamp in seconds.

In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.

The filter accepts the following options:


=over 4



=item B<amount>

Set the percentage of the pixels that have to be below the threshold, defaults
to C<98>.


=item B<threshold, thresh>

Set the threshold below which a pixel value is considered black, defaults to
C<32>.


=back



=head2 blend


Blend two video frames into each other.

It takes two input streams and outputs one stream, the first input is the
"top" layer and second input is "bottom" layer.
Output terminates when shortest input terminates.

A description of the accepted options follows.


=over 4


=item B<c0_mode>


=item B<c1_mode>


=item B<c2_mode>


=item B<c3_mode>


=item B<all_mode>

Set blend mode for specific pixel component or all pixel components in case
of I<all_mode>. Default value is C<normal>.

Available values for component modes are:

=over 4


=item B<addition>


=item B<and>


=item B<average>


=item B<burn>


=item B<darken>


=item B<difference>


=item B<divide>


=item B<dodge>


=item B<exclusion>


=item B<hardlight>


=item B<lighten>


=item B<multiply>


=item B<negation>


=item B<normal>


=item B<or>


=item B<overlay>


=item B<phoenix>


=item B<pinlight>


=item B<reflect>


=item B<screen>


=item B<softlight>


=item B<subtract>


=item B<vividlight>


=item B<xor>


=back



=item B<c0_opacity>


=item B<c1_opacity>


=item B<c2_opacity>


=item B<c3_opacity>


=item B<all_opacity>

Set blend opacity for specific pixel component or all pixel components in case
of I<all_opacity>. Only used in combination with pixel component blend modes.


=item B<c0_expr>


=item B<c1_expr>


=item B<c2_expr>


=item B<c3_expr>


=item B<all_expr>

Set blend expression for specific pixel component or all pixel components in case
of I<all_expr>. Note that related mode options will be ignored if those are set.

The expressions can use the following variables:


=over 4


=item B<N>

The sequential number of the filtered frame, starting from C<0>.


=item B<X>


=item B<Y>

the coordinates of the current sample


=item B<W>


=item B<H>

the width and height of currently filtered plane


=item B<SW>


=item B<SH>

Width and height scale depending on the currently filtered plane. It is the
ratio between the corresponding luma plane number of pixels and the current
plane ones. E.g. for YUV4:2:0 the values are C<1,1> for the luma plane, and
C<0.5,0.5> for chroma planes.


=item B<T>

Time of the current frame, expressed in seconds.


=item B<TOP, A>

Value of pixel component at current location for first video frame (top layer).


=item B<BOTTOM, B>

Value of pixel component at current location for second video frame (bottom layer).

=back


=back



=head3 Examples



=over 4


=item *

Apply transition from bottom layer to top layer in first 10 seconds:
	
	blend=all_expr='A*(if(gte(T,10),1,T/10))+B*(1-(if(gte(T,10),1,T/10)))'



=item *

Apply 1x1 checkerboard effect:
	
	blend=all_expr='if(eq(mod(X,2),mod(Y,2)),A,B)'


=back



=head2 boxblur


Apply boxblur algorithm to the input video.

The filter accepts the following options:


=over 4



=item B<luma_radius, lr>


=item B<luma_power, lp>


=item B<chroma_radius, cr>


=item B<chroma_power, cp>


=item B<alpha_radius, ar>


=item B<alpha_power, ap>



=back


A description of the accepted options follows.


=over 4


=item B<luma_radius, lr>


=item B<chroma_radius, cr>


=item B<alpha_radius, ar>

Set an expression for the box radius in pixels used for blurring the
corresponding input plane.

The radius value must be a non-negative number, and must not be
greater than the value of the expression C<min(w,h)/2> for the
luma and alpha planes, and of C<min(cw,ch)/2> for the chroma
planes.

Default value for B<luma_radius> is "2". If not specified,
B<chroma_radius> and B<alpha_radius> default to the
corresponding value set for B<luma_radius>.

The expressions can contain the following constants:

=over 4


=item B<w, h>

the input width and height in pixels


=item B<cw, ch>

the input chroma image width and height in pixels


=item B<hsub, vsub>

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" I<hsub> is 2 and I<vsub> is 1.

=back



=item B<luma_power, lp>


=item B<chroma_power, cp>


=item B<alpha_power, ap>

Specify how many times the boxblur filter is applied to the
corresponding plane.

Default value for B<luma_power> is 2. If not specified,
B<chroma_power> and B<alpha_power> default to the
corresponding value set for B<luma_power>.

A value of 0 will disable the effect.

=back



=head3 Examples



=over 4


=item *

Apply a boxblur filter with luma, chroma, and alpha radius
set to 2:
	
	boxblur=luma_radius=2:luma_power=1
	boxblur=2:1



=item *

Set luma radius to 2, alpha and chroma radius to 0:
	
	boxblur=2:1:cr=0:ar=0



=item *

Set luma and chroma radius to a fraction of the video dimension:
	
	boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1


=back



=head2 colorbalance

Modify intensity of primary colors (red, green and blue) of input frames.

The filter allows an input frame to be adjusted in the shadows, midtones or highlights
regions for the red-cyan, green-magenta or blue-yellow balance.

A positive adjustment value shifts the balance towards the primary color, a negative
value towards the complementary color.

The filter accepts the following options:


=over 4


=item B<rs>


=item B<gs>


=item B<bs>

Adjust red, green and blue shadows (darkest pixels).


=item B<rm>


=item B<gm>


=item B<bm>

Adjust red, green and blue midtones (medium pixels).


=item B<rh>


=item B<gh>


=item B<bh>

Adjust red, green and blue highlights (brightest pixels).

Allowed ranges for options are C<[-1.0, 1.0]>. Defaults are C<0>.

=back



=head3 Examples



=over 4


=item *

Add red color cast to shadows:
	
	colorbalance=rs=.3


=back



=head2 colorchannelmixer


Adjust video input frames by re-mixing color channels.

This filter modifies a color channel by adding the values associated to
the other channels of the same pixels. For example if the value to
modify is red, the output value will be:
	
	<red>=<red>*<rr> + <blue>*<rb> + <green>*<rg> + <alpha>*<ra>


The filter accepts the following options:


=over 4


=item B<rr>


=item B<rg>


=item B<rb>


=item B<ra>

Adjust contribution of input red, green, blue and alpha channels for output red channel.
Default is C<1> for I<rr>, and C<0> for I<rg>, I<rb> and I<ra>.


=item B<gr>


=item B<gg>


=item B<gb>


=item B<ga>

Adjust contribution of input red, green, blue and alpha channels for output green channel.
Default is C<1> for I<gg>, and C<0> for I<gr>, I<gb> and I<ga>.


=item B<br>


=item B<bg>


=item B<bb>


=item B<ba>

Adjust contribution of input red, green, blue and alpha channels for output blue channel.
Default is C<1> for I<bb>, and C<0> for I<br>, I<bg> and I<ba>.


=item B<ar>


=item B<ag>


=item B<ab>


=item B<aa>

Adjust contribution of input red, green, blue and alpha channels for output alpha channel.
Default is C<1> for I<aa>, and C<0> for I<ar>, I<ag> and I<ab>.

Allowed ranges for options are C<[-2.0, 2.0]>.

=back



=head3 Examples



=over 4


=item *

Convert source to grayscale:
	
	colorchannelmixer=.3:.4:.3:0:.3:.4:.3:0:.3:.4:.3


=back



=head2 colormatrix


Convert color matrix.

The filter accepts the following options:


=over 4


=item B<src>


=item B<dst>

Specify the source and destination color matrix. Both values must be
specified.

The accepted values are:

=over 4


=item B<bt709>

BT.709


=item B<bt601>

BT.601


=item B<smpte240m>

SMPTE-240M


=item B<fcc>

FCC

=back


=back


For example to convert from BT.601 to SMPTE-240M, use the command:
	
	colormatrix=bt601:smpte240m



=head2 copy


Copy the input source unchanged to the output. Mainly useful for
testing purposes.


=head2 crop


Crop the input video to given dimensions.

The filter accepts the following options:


=over 4


=item B<w, out_w>

Width of the output video. It defaults to C<iw>.
This expression is evaluated only once during the filter
configuration.


=item B<h, out_h>

Height of the output video. It defaults to C<ih>.
This expression is evaluated only once during the filter
configuration.


=item B<x>

Horizontal position, in the input video, of the left edge of the output video.
It defaults to C<(in_w-out_w)/2>.
This expression is evaluated per-frame.


=item B<y>

Vertical position, in the input video, of the top edge of the output video.
It defaults to C<(in_h-out_h)/2>.
This expression is evaluated per-frame.


=item B<keep_aspect>

If set to 1 will force the output display aspect ratio
to be the same of the input, by changing the output sample aspect
ratio. It defaults to 0.

=back


The I<out_w>, I<out_h>, I<x>, I<y> parameters are
expressions containing the following constants:


=over 4


=item B<x, y>

the computed values for I<x> and I<y>. They are evaluated for
each new frame.


=item B<in_w, in_h>

the input width and height


=item B<iw, ih>

same as I<in_w> and I<in_h>


=item B<out_w, out_h>

the output (cropped) width and height


=item B<ow, oh>

same as I<out_w> and I<out_h>


=item B<a>

same as I<iw> / I<ih>


=item B<sar>

input sample aspect ratio


=item B<dar>

input display aspect ratio, it is the same as (I<iw> / I<ih>) * I<sar>


=item B<hsub, vsub>

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" I<hsub> is 2 and I<vsub> is 1.


=item B<n>

the number of input frame, starting from 0


=item B<pos>

the position in the file of the input frame, NAN if unknown


=item B<t>

timestamp expressed in seconds, NAN if the input timestamp is unknown


=back


The expression for I<out_w> may depend on the value of I<out_h>,
and the expression for I<out_h> may depend on I<out_w>, but they
cannot depend on I<x> and I<y>, as I<x> and I<y> are
evaluated after I<out_w> and I<out_h>.

The I<x> and I<y> parameters specify the expressions for the
position of the top-left corner of the output (non-cropped) area. They
are evaluated for each frame. If the evaluated value is not valid, it
is approximated to the nearest valid value.

The expression for I<x> may depend on I<y>, and the expression
for I<y> may depend on I<x>.


=head3 Examples



=over 4


=item *

Crop area with size 100x100 at position (12,34).
	
	crop=100:100:12:34


Using named options, the example above becomes:
	
	crop=w=100:h=100:x=12:y=34



=item *

Crop the central input area with size 100x100:
	
	crop=100:100



=item *

Crop the central input area with size 2/3 of the input video:
	
	crop=2/3*in_w:2/3*in_h



=item *

Crop the input video central square:
	
	crop=out_w=in_h
	crop=in_h



=item *

Delimit the rectangle with the top-left corner placed at position
100:100 and the right-bottom corner corresponding to the right-bottom
corner of the input image:
	
	crop=in_w-100:in_h-100:100:100



=item *

Crop 10 pixels from the left and right borders, and 20 pixels from
the top and bottom borders
	
	crop=in_w-2*10:in_h-2*20



=item *

Keep only the bottom right quarter of the input image:
	
	crop=in_w/2:in_h/2:in_w/2:in_h/2



=item *

Crop height for getting Greek harmony:
	
	crop=in_w:1/PHI*in_w



=item *

Appply trembling effect:
	
	crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)



=item *

Apply erratic camera effect depending on timestamp:
	
	crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"



=item *

Set x depending on the value of y:
	
	crop=in_w/2:in_h/2:y:10+10*sin(n/10)


=back



=head2 cropdetect


Auto-detect crop size.

Calculate necessary cropping parameters and prints the recommended
parameters through the logging system. The detected dimensions
correspond to the non-black area of the input video.

The filter accepts the following options:


=over 4



=item B<limit>

Set higher black value threshold, which can be optionally specified
from nothing (0) to everything (255). An intensity value greater
to the set value is considered non-black. Default value is 24.


=item B<round>

Set the value for which the width/height should be divisible by. The
offset is automatically adjusted to center the video. Use 2 to get
only even dimensions (needed for 4:2:2 video). 16 is best when
encoding to most video codecs. Default value is 16.


=item B<reset_count, reset>

Set the counter that determines after how many frames cropdetect will
reset the previously detected largest video area and start over to
detect the current optimal crop area. Default value is 0.

This can be useful when channel logos distort the video area. 0
indicates never reset and return the largest area encountered during
playback.

=back



=head2 curves


Apply color adjustments using curves.

This filter is similar to the Adobe Photoshop and GIMP curves tools. Each
component (red, green and blue) has its values defined by I<N> key points
tied from each other using a smooth curve. The x-axis represents the pixel
values from the input frame, and the y-axis the new pixel values to be set for
the output frame.

By default, a component curve is defined by the two points I<(0;0)> and
I<(1;1)>. This creates a straight line where each original pixel value is
"adjusted" to its own value, which means no change to the image.

The filter allows you to redefine these two points and add some more. A new
curve (using a natural cubic spline interpolation) will be define to pass
smoothly through all these new coordinates. The new defined points needs to be
strictly increasing over the x-axis, and their I<x> and I<y> values must
be in the I<[0;1]> interval.  If the computed curves happened to go outside
the vector spaces, the values will be clipped accordingly.

If there is no key point defined in C<x=0>, the filter will automatically
insert a I<(0;0)> point. In the same way, if there is no key point defined
in C<x=1>, the filter will automatically insert a I<(1;1)> point.

The filter accepts the following options:


=over 4


=item B<preset>

Select one of the available color presets. This option can be used in addition
to the B<r>, B<g>, B<b> parameters; in this case, the later
options takes priority on the preset values.
Available presets are:

=over 4


=item B<none>


=item B<color_negative>


=item B<cross_process>


=item B<darker>


=item B<increase_contrast>


=item B<lighter>


=item B<linear_contrast>


=item B<medium_contrast>


=item B<negative>


=item B<strong_contrast>


=item B<vintage>


=back

Default is C<none>.

=item B<master, m>

Set the master key points. These points will define a second pass mapping. It
is sometimes called a "luminance" or "value" mapping. It can be used with
B<r>, B<g>, B<b> or B<all> since it acts like a
post-processing LUT.

=item B<red, r>

Set the key points for the red component.

=item B<green, g>

Set the key points for the green component.

=item B<blue, b>

Set the key points for the blue component.

=item B<all>

Set the key points for all components (not including master).
Can be used in addition to the other key points component
options. In this case, the unset component(s) will fallback on this
B<all> setting.

=item B<psfile>

Specify a Photoshop curves file (C<.asv>) to import the settings from.

=back


To avoid some filtergraph syntax conflicts, each key points list need to be
defined using the following syntax: C<x0/y0 x1/y1 x2/y2 ...>.


=head3 Examples



=over 4


=item *

Increase slightly the middle level of blue:
	
	curves=blue='0.5/0.58'



=item *

Vintage effect:
	
	curves=r='0/0.11 .42/.51 1/0.95':g='0.50/0.48':b='0/0.22 .49/.44 1/0.8'

Here we obtain the following coordinates for each components:

=over 4


=item I<red>

C<(0;0.11) (0.42;0.51) (1;0.95)>

=item I<green>

C<(0;0) (0.50;0.48) (1;1)>

=item I<blue>

C<(0;0.22) (0.49;0.44) (1;0.80)>

=back



=item *

The previous example can also be achieved with the associated built-in preset:
	
	curves=preset=vintage



=item *

Or simply:
	
	curves=vintage



=item *

Use a Photoshop preset and redefine the points of the green component:
	
	curves=psfile='MyCurvesPresets/purple.asv':green='0.45/0.53'


=back




=head2 decimate


Drop duplicated frames at regular intervals.

The filter accepts the following options:


=over 4


=item B<cycle>

Set the number of frames from which one will be dropped. Setting this to
I<N> means one frame in every batch of I<N> frames will be dropped.
Default is C<5>.


=item B<dupthresh>

Set the threshold for duplicate detection. If the difference metric for a frame
is less than or equal to this value, then it is declared as duplicate. Default
is C<1.1>


=item B<scthresh>

Set scene change threshold. Default is C<15>.


=item B<blockx>


=item B<blocky>

Set the size of the x and y-axis blocks used during metric calculations.
Larger blocks give better noise suppression, but also give worse detection of
small movements. Must be a power of two. Default is C<32>.


=item B<ppsrc>

Mark main input as a pre-processed input and activate clean source input
stream. This allows the input to be pre-processed with various filters to help
the metrics calculation while keeping the frame selection lossless. When set to
C<1>, the first stream is for the pre-processed input, and the second
stream is the clean source from where the kept frames are chosen. Default is
C<0>.


=item B<chroma>

Set whether or not chroma is considered in the metric calculations. Default is
C<1>.

=back



=head2 delogo


Suppress a TV station logo by a simple interpolation of the surrounding
pixels. Just set a rectangle covering the logo and watch it disappear
(and sometimes something even uglier appear - your mileage may vary).

This filter accepts the following options:

=over 4



=item B<x, y>

Specify the top left corner coordinates of the logo. They must be
specified.


=item B<w, h>

Specify the width and height of the logo to clear. They must be
specified.


=item B<band, t>

Specify the thickness of the fuzzy edge of the rectangle (added to
I<w> and I<h>). The default value is 4.


=item B<show>

When set to 1, a green rectangle is drawn on the screen to simplify
finding the right I<x>, I<y>, I<w>, I<h> parameters, and
I<band> is set to 4. The default value is 0.


=back



=head3 Examples



=over 4


=item *

Set a rectangle covering the area with top left corner coordinates 0,0
and size 100x77, setting a band of size 10:
	
	delogo=x=0:y=0:w=100:h=77:band=10



=back



=head2 deshake


Attempt to fix small changes in horizontal and/or vertical shift. This
filter helps remove camera shake from hand-holding a camera, bumping a
tripod, moving on a vehicle, etc.

The filter accepts the following options:


=over 4



=item B<x>


=item B<y>


=item B<w>


=item B<h>

Specify a rectangular area where to limit the search for motion
vectors.
If desired the search for motion vectors can be limited to a
rectangular area of the frame defined by its top left corner, width
and height. These parameters have the same meaning as the drawbox
filter which can be used to visualise the position of the bounding
box.

This is useful when simultaneous movement of subjects within the frame
might be confused for camera motion by the motion vector search.

If any or all of I<x>, I<y>, I<w> and I<h> are set to -1
then the full frame is used. This allows later options to be set
without specifying the bounding box for the motion vector search.

Default - search the whole frame.


=item B<rx>


=item B<ry>

Specify the maximum extent of movement in x and y directions in the
range 0-64 pixels. Default 16.


=item B<edge>

Specify how to generate pixels to fill blanks at the edge of the
frame. Available values are:

=over 4


=item B<blank, 0>

Fill zeroes at blank locations

=item B<original, 1>

Original image at blank locations

=item B<clamp, 2>

Extruded edge value at blank locations

=item B<mirror, 3>

Mirrored edge at blank locations

=back

Default value is B<mirror>.


=item B<blocksize>

Specify the blocksize to use for motion search. Range 4-128 pixels,
default 8.


=item B<contrast>

Specify the contrast threshold for blocks. Only blocks with more than
the specified contrast (difference between darkest and lightest
pixels) will be considered. Range 1-255, default 125.


=item B<search>

Specify the search strategy. Available values are:

=over 4


=item B<exhaustive, 0>

Set exhaustive search

=item B<less, 1>

Set less exhaustive search.

=back

Default value is B<exhaustive>.


=item B<filename>

If set then a detailed log of the motion search is written to the
specified file.


=item B<opencl>

If set to 1, specify using OpenCL capabilities, only available if
FFmpeg was configured with C<--enable-opencl>. Default value is 0.


=back



=head2 drawbox


Draw a colored box on the input image.

This filter accepts the following options:


=over 4


=item B<x, y>

Specify the top left corner coordinates of the box. Default to 0.


=item B<width, w>


=item B<height, h>

Specify the width and height of the box, if 0 they are interpreted as
the input width and height. Default to 0.


=item B<color, c>

Specify the color of the box to write, it can be the name of a color
(case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
value C<invert> is used, the box edge color is the same as the
video with inverted luma.


=item B<thickness, t>

Set the thickness of the box edge. Default value is C<4>.

=back



=head3 Examples



=over 4


=item *

Draw a black box around the edge of the input image:
	
	drawbox



=item *

Draw a box with color red and an opacity of 50%:
	
	drawbox=10:20:200:60:red@0.5


The previous example can be specified as:
	
	drawbox=x=10:y=20:w=200:h=60:color=red@0.5



=item *

Fill the box with pink color:
	
	drawbox=x=10:y=10:w=100:h=100:color=pink@0.5:t=max


=back




=head2 drawtext


Draw text string or text from specified file on top of video using the
libfreetype library.

To enable compilation of this filter you need to configure FFmpeg with
C<--enable-libfreetype>.


=head3 Syntax


The description of the accepted parameters follows.


=over 4



=item B<box>

Used to draw a box around text using background color.
Value should be either 1 (enable) or 0 (disable).
The default value of I<box> is 0.


=item B<boxcolor>

The color to be used for drawing box around text.
Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
(e.g. "0xff00ff"), possibly followed by an alpha specifier.
The default value of I<boxcolor> is "white".


=item B<draw>

Set an expression which specifies if the text should be drawn. If the
expression evaluates to 0, the text is not drawn. This is useful for
specifying that the text should be drawn only when specific conditions
are met.

Default value is "1".

See below for the list of accepted constants and functions.


=item B<expansion>

Select how the I<text> is expanded. Can be either C<none>,
C<strftime> (deprecated) or
C<normal> (default). See the drawtext_expansion, Text expansion section
below for details.


=item B<fix_bounds>

If true, check and fix text coords to avoid clipping.


=item B<fontcolor>

The color to be used for drawing fonts.
Either a string (e.g. "red") or in 0xRRGGBB[AA] format
(e.g. "0xff000033"), possibly followed by an alpha specifier.
The default value of I<fontcolor> is "black".


=item B<fontfile>

The font file to be used for drawing text. Path must be included.
This parameter is mandatory.


=item B<fontsize>

The font size to be used for drawing text.
The default value of I<fontsize> is 16.


=item B<ft_load_flags>

Flags to be used for loading the fonts.

The flags map the corresponding flags supported by libfreetype, and are
a combination of the following values:

=over 4


=item I<default>


=item I<no_scale>


=item I<no_hinting>


=item I<render>


=item I<no_bitmap>


=item I<vertical_layout>


=item I<force_autohint>


=item I<crop_bitmap>


=item I<pedantic>


=item I<ignore_global_advance_width>


=item I<no_recurse>


=item I<ignore_transform>


=item I<monochrome>


=item I<linear_design>


=item I<no_autohint>


=item I<end table>


=back


Default value is "render".

For more information consult the documentation for the FT_LOAD_*
libfreetype flags.


=item B<shadowcolor>

The color to be used for drawing a shadow behind the drawn text.  It
can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
The default value of I<shadowcolor> is "black".


=item B<shadowx, shadowy>

The x and y offsets for the text shadow position with respect to the
position of the text. They can be either positive or negative
values. Default value for both is "0".


=item B<tabsize>

The size in number of spaces to use for rendering the tab.
Default value is 4.


=item B<timecode>

Set the initial timecode representation in "hh:mm:ss[:;.]ff"
format. It can be used with or without text parameter. I<timecode_rate>
option must be specified.


=item B<timecode_rate, rate, r>

Set the timecode frame rate (timecode only).


=item B<text>

The text string to be drawn. The text must be a sequence of UTF-8
encoded characters.
This parameter is mandatory if no file is specified with the parameter
I<textfile>.


=item B<textfile>

A text file containing text to be drawn. The text must be a sequence
of UTF-8 encoded characters.

This parameter is mandatory if no text string is specified with the
parameter I<text>.

If both I<text> and I<textfile> are specified, an error is thrown.


=item B<reload>

If set to 1, the I<textfile> will be reloaded before each frame.
Be sure to update it atomically, or it may be read partially, or even fail.


=item B<x, y>

The expressions which specify the offsets where text will be drawn
within the video frame. They are relative to the top/left border of the
output image.

The default value of I<x> and I<y> is "0".

See below for the list of accepted constants and functions.

=back


The parameters for I<x> and I<y> are expressions containing the
following constants and functions:


=over 4


=item B<dar>

input display aspect ratio, it is the same as (I<w> / I<h>) * I<sar>


=item B<hsub, vsub>

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" I<hsub> is 2 and I<vsub> is 1.


=item B<line_h, lh>

the height of each text line


=item B<main_h, h, H>

the input height


=item B<main_w, w, W>

the input width


=item B<max_glyph_a, ascent>

the maximum distance from the baseline to the highest/upper grid
coordinate used to place a glyph outline point, for all the rendered
glyphs.
It is a positive value, due to the grid's orientation with the Y axis
upwards.


=item B<max_glyph_d, descent>

the maximum distance from the baseline to the lowest grid coordinate
used to place a glyph outline point, for all the rendered glyphs.
This is a negative value, due to the grid's orientation, with the Y axis
upwards.


=item B<max_glyph_h>

maximum glyph height, that is the maximum height for all the glyphs
contained in the rendered text, it is equivalent to I<ascent> -
I<descent>.


=item B<max_glyph_w>

maximum glyph width, that is the maximum width for all the glyphs
contained in the rendered text


=item B<n>

the number of input frame, starting from 0


=item B<rand(min, max)>

return a random number included between I<min> and I<max>


=item B<sar>

input sample aspect ratio


=item B<t>

timestamp expressed in seconds, NAN if the input timestamp is unknown


=item B<text_h, th>

the height of the rendered text


=item B<text_w, tw>

the width of the rendered text


=item B<x, y>

the x and y offset coordinates where the text is drawn.

These parameters allow the I<x> and I<y> expressions to refer
each other, so you can for example specify C<y=x/dar>.

=back


If libavfilter was built with C<--enable-fontconfig>, then
B<fontfile> can be a fontconfig pattern or omitted.



=head3 Text expansion


If B<expansion> is set to C<strftime>,
the filter recognizes strftime() sequences in the provided text and
expands them accordingly. Check the documentation of strftime(). This
feature is deprecated.

If B<expansion> is set to C<none>, the text is printed verbatim.

If B<expansion> is set to C<normal> (which is the default),
the following expansion mechanism is used.

The backslash character '\', followed by any character, always expands to
the second character.

Sequence of the form C<%{...}> are expanded. The text between the
braces is a function name, possibly followed by arguments separated by ':'.
If the arguments contain special characters or delimiters (':' or '}'),
they should be escaped.

Note that they probably must also be escaped as the value for the
B<text> option in the filter argument string and as the filter
argument in the filtergraph description, and possibly also for the shell,
that makes up to four levels of escaping; using a text file avoids these
problems.

The following functions are available:


=over 4



=item B<expr, e>

The expression evaluation result.

It must take one argument specifying the expression to be evaluated,
which accepts the same constants and functions as the I<x> and
I<y> values. Note that not all constants should be used, for
example the text size is not known when evaluating the expression, so
the constants I<text_w> and I<text_h> will have an undefined
value.


=item B<gmtime>

The time at which the filter is running, expressed in UTC.
It can accept an argument: a strftime() format string.


=item B<localtime>

The time at which the filter is running, expressed in the local time zone.
It can accept an argument: a strftime() format string.


=item B<n, frame_num>

The frame number, starting from 0.


=item B<pts>

The timestamp of the current frame, in seconds, with microsecond accuracy.


=back



=head3 Examples



=over 4


=item *

Draw "Test Text" with font FreeSerif, using the default values for the
optional parameters.

	
	drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"



=item *

Draw 'Test Text' with font FreeSerif of size 24 at position x=100
and y=50 (counting from the top-left corner of the screen), text is
yellow with a red box around it. Both the text and the box have an
opacity of 20%.

	
	drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
	          x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"


Note that the double quotes are not necessary if spaces are not used
within the parameter list.


=item *

Show the text at the center of the video frame:
	
	drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"



=item *

Show a text line sliding from right to left in the last row of the video
frame. The file F<LONG_LINE> is assumed to contain a single line
with no newlines.
	
	drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"



=item *

Show the content of file F<CREDITS> off the bottom of the frame and scroll up.
	
	drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"



=item *

Draw a single green letter "g", at the center of the input video.
The glyph baseline is placed at half screen height.
	
	drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"



=item *

Show text for 1 second every 3 seconds:
	
	drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"



=item *

Use fontconfig to set the font. Note that the colons need to be escaped.
	
	drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'



=item *

Print the date of a real-time encoding (see strftime(3)):
	
	drawtext='fontfile=FreeSans.ttf:text=%{localtime:%a %b %d %Y}'



=back


For more information about libfreetype, check:
E<lt>B<http://www.freetype.org/>E<gt>.

For more information about fontconfig, check:
E<lt>B<http://freedesktop.org/software/fontconfig/fontconfig-user.html>E<gt>.


=head2 edgedetect


Detect and draw edges. The filter uses the Canny Edge Detection algorithm.

The filter accepts the following options:


=over 4


=item B<low, high>

Set low and high threshold values used by the Canny thresholding
algorithm.

The high threshold selects the "strong" edge pixels, which are then
connected through 8-connectivity with the "weak" edge pixels selected
by the low threshold.

I<low> and I<high> threshold values must be choosen in the range
[0,1], and I<low> should be lesser or equal to I<high>.

Default value for I<low> is C<20/255>, and default value for I<high>
is C<50/255>.

=back


Example:
	
	edgedetect=low=0.1:high=0.4



=head2 fade


Apply fade-in/out effect to input video.

This filter accepts the following options:


=over 4


=item B<type, t>

The effect type -- can be either "in" for fade-in, or "out" for a fade-out
effect.
Default is C<in>.


=item B<start_frame, s>

Specify the number of the start frame for starting to apply the fade
effect. Default is 0.


=item B<nb_frames, n>

The number of frames for which the fade effect has to last. At the end of the
fade-in effect the output video will have the same intensity as the input video,
at the end of the fade-out transition the output video will be completely black.
Default is 25.


=item B<alpha>

If set to 1, fade only alpha channel, if one exists on the input.
Default value is 0.

=back



=head3 Examples



=over 4


=item *

Fade in first 30 frames of video:
	
	fade=in:0:30


The command above is equivalent to:
	
	fade=t=in:s=0:n=30



=item *

Fade out last 45 frames of a 200-frame video:
	
	fade=out:155:45
	fade=type=out:start_frame=155:nb_frames=45



=item *

Fade in first 25 frames and fade out last 25 frames of a 1000-frame video:
	
	fade=in:0:25, fade=out:975:25



=item *

Make first 5 frames black, then fade in from frame 5-24:
	
	fade=in:5:20



=item *

Fade in alpha over first 25 frames of video:
	
	fade=in:0:25:alpha=1


=back



=head2 field


Extract a single field from an interlaced image using stride
arithmetic to avoid wasting CPU time. The output frames are marked as
non-interlaced.

The filter accepts the following options:


=over 4


=item B<type>

Specify whether to extract the top (if the value is C<0> or
C<top>) or the bottom field (if the value is C<1> or
C<bottom>).

=back



=head2 fieldmatch


Field matching filter for inverse telecine. It is meant to reconstruct the
progressive frames from a telecined stream. The filter does not drop duplicated
frames, so to achieve a complete inverse telecine C<fieldmatch> needs to be
followed by a decimation filter such as decimate in the filtergraph.

The separation of the field matching and the decimation is notably motivated by
the possibility of inserting a de-interlacing filter fallback between the two.
If the source has mixed telecined and real interlaced content,
C<fieldmatch> will not be able to match fields for the interlaced parts.
But these remaining combed frames will be marked as interlaced, and thus can be
de-interlaced by a later filter such as yadif before decimation.

In addition to the various configuration options, C<fieldmatch> can take an
optional second stream, activated through the B<ppsrc> option. If
enabled, the frames reconstruction will be based on the fields and frames from
this second stream. This allows the first input to be pre-processed in order to
help the various algorithms of the filter, while keeping the output lossless
(assuming the fields are matched properly). Typically, a field-aware denoiser,
or brightness/contrast adjustments can help.

Note that this filter uses the same algorithms as TIVTC/TFM (AviSynth project)
and VIVTC/VFM (VapourSynth project). The later is a light clone of TFM from
which C<fieldmatch> is based on. While the semantic and usage are very
close, some behaviour and options names can differ.

The filter accepts the following options:


=over 4


=item B<order>

Specify the assumed field order of the input stream. Available values are:


=over 4


=item B<auto>

Auto detect parity (use FFmpeg's internal parity value).

=item B<bff>

Assume bottom field first.

=item B<tff>

Assume top field first.

=back


Note that it is sometimes recommended not to trust the parity announced by the
stream.

Default value is I<auto>.


=item B<mode>

Set the matching mode or strategy to use. B<pc> mode is the safest in the
sense that it wont risk creating jerkiness due to duplicate frames when
possible, but if there are bad edits or blended fields it will end up
outputting combed frames when a good match might actually exist. On the other
hand, B<pcn_ub> mode is the most risky in terms of creating jerkiness,
but will almost always find a good frame if there is one. The other values are
all somewhere in between B<pc> and B<pcn_ub> in terms of risking
jerkiness and creating duplicate frames versus finding good matches in sections
with bad edits, orphaned fields, blended fields, etc.

More details about p/c/n/u/b are available in p/c/n/u/b meaning section.

Available values are:


=over 4


=item B<pc>

2-way matching (p/c)

=item B<pc_n>

2-way matching, and trying 3rd match if still combed (p/c + n)

=item B<pc_u>

2-way matching, and trying 3rd match (same order) if still combed (p/c + u)

=item B<pc_n_ub>

2-way matching, trying 3rd match if still combed, and trying 4th/5th matches if
still combed (p/c + n + u/b)

=item B<pcn>

3-way matching (p/c/n)

=item B<pcn_ub>

3-way matching, and trying 4th/5th matches if all 3 of the original matches are
detected as combed (p/c/n + u/b)

=back


The parenthesis at the end indicate the matches that would be used for that
mode assuming B<order>=I<tff> (and B<field> on I<auto> or
I<top>).

In terms of speed B<pc> mode is by far the fastest and B<pcn_ub> is
the slowest.

Default value is I<pc_n>.


=item B<ppsrc>

Mark the main input stream as a pre-processed input, and enable the secondary
input stream as the clean source to pick the fields from. See the filter
introduction for more details. It is similar to the B<clip2> feature from
VFM/TFM.

Default value is C<0> (disabled).


=item B<field>

Set the field to match from. It is recommended to set this to the same value as
B<order> unless you experience matching failures with that setting. In
certain circumstances changing the field that is used to match from can have a
large impact on matching performance. Available values are:


=over 4


=item B<auto>

Automatic (same value as B<order>).

=item B<bottom>

Match from the bottom field.

=item B<top>

Match from the top field.

=back


Default value is I<auto>.


=item B<mchroma>

Set whether or not chroma is included during the match comparisons. In most
cases it is recommended to leave this enabled. You should set this to C<0>
only if your clip has bad chroma problems such as heavy rainbowing or other
artifacts. Setting this to C<0> could also be used to speed things up at
the cost of some accuracy.

Default value is C<1>.


=item B<y0>


=item B<y1>

These define an exclusion band which excludes the lines between B<y0> and
B<y1> from being included in the field matching decision. An exclusion
band can be used to ignore subtitles, a logo, or other things that may
interfere with the matching. B<y0> sets the starting scan line and
B<y1> sets the ending line; all lines in between B<y0> and
B<y1> (including B<y0> and B<y1>) will be ignored. Setting
B<y0> and B<y1> to the same value will disable the feature.
B<y0> and B<y1> defaults to C<0>.


=item B<scthresh>

Set the scene change detection threshold as a percentage of maximum change on
the luma plane. Good values are in the C<[8.0, 14.0]> range. Scene change
detection is only relevant in case B<combmatch>=I<sc>.  The range for
B<scthresh> is C<[0.0, 100.0]>.

Default value is C<12.0>.


=item B<combmatch>

When B<combatch> is not I<none>, C<fieldmatch> will take into
account the combed scores of matches when deciding what match to use as the
final match. Available values are:


=over 4


=item B<none>

No final matching based on combed scores.

=item B<sc>

Combed scores are only used when a scene change is detected.

=item B<full>

Use combed scores all the time.

=back


Default is I<sc>.


=item B<combdbg>

Force C<fieldmatch> to calculate the combed metrics for certain matches and
print them. This setting is known as B<micout> in TFM/VFM vocabulary.
Available values are:


=over 4


=item B<none>

No forced calculation.

=item B<pcn>

Force p/c/n calculations.

=item B<pcnub>

Force p/c/n/u/b calculations.

=back


Default value is I<none>.


=item B<cthresh>

This is the area combing threshold used for combed frame detection. This
essentially controls how "strong" or "visible" combing must be to be detected.
Larger values mean combing must be more visible and smaller values mean combing
can be less visible or strong and still be detected. Valid settings are from
C<-1> (every pixel will be detected as combed) to C<255> (no pixel will
be detected as combed). This is basically a pixel difference value. A good
range is C<[8, 12]>.

Default value is C<9>.


=item B<chroma>

Sets whether or not chroma is considered in the combed frame decision.  Only
disable this if your source has chroma problems (rainbowing, etc.) that are
causing problems for the combed frame detection with chroma enabled. Actually,
using B<chroma>=I<0> is usually more reliable, except for the case
where there is chroma only combing in the source.

Default value is C<0>.


=item B<blockx>


=item B<blocky>

Respectively set the x-axis and y-axis size of the window used during combed
frame detection. This has to do with the size of the area in which
B<combpel> pixels are required to be detected as combed for a frame to be
declared combed. See the B<combpel> parameter description for more info.
Possible values are any number that is a power of 2 starting at 4 and going up
to 512.

Default value is C<16>.


=item B<combpel>

The number of combed pixels inside any of the B<blocky> by
B<blockx> size blocks on the frame for the frame to be detected as
combed. While B<cthresh> controls how "visible" the combing must be, this
setting controls "how much" combing there must be in any localized area (a
window defined by the B<blockx> and B<blocky> settings) on the
frame. Minimum value is C<0> and maximum is C<blocky x blockx> (at
which point no frames will ever be detected as combed). This setting is known
as B<MI> in TFM/VFM vocabulary.

Default value is C<80>.

=back




=head3 p/c/n/u/b meaning



=head4 p/c/n


We assume the following telecined stream:

	
	Top fields:     1 2 2 3 4
	Bottom fields:  1 2 3 4 4


The numbers correspond to the progressive frame the fields relate to. Here, the
first two frames are progressive, the 3rd and 4th are combed, and so on.

When C<fieldmatch> is configured to run a matching from bottom
(B<field>=I<bottom>) this is how this input stream get transformed:

	
	Input stream:
	                T     1 2 2 3 4
	                B     1 2 3 4 4   <-- matching reference
	
	Matches:              c c n n c
	
	Output stream:
	                T     1 2 3 4 4
	                B     1 2 3 4 4


As a result of the field matching, we can see that some frames get duplicated.
To perform a complete inverse telecine, you need to rely on a decimation filter
after this operation. See for instance the decimate filter.

The same operation now matching from top fields (B<field>=I<top>)
looks like this:

	
	Input stream:
	                T     1 2 2 3 4   <-- matching reference
	                B     1 2 3 4 4
	
	Matches:              c c p p c
	
	Output stream:
	                T     1 2 2 3 4
	                B     1 2 2 3 4


In these examples, we can see what I<p>, I<c> and I<n> mean;
basically, they refer to the frame and field of the opposite parity:


=over 4


=item *<I<p> matches the field of the opposite parity in the previous frame>


=item *<I<c> matches the field of the opposite parity in the current frame>


=item *<I<n> matches the field of the opposite parity in the next frame>


=back



=head4 u/b


The I<u> and I<b> matching are a bit special in the sense that they match
from the opposite parity flag. In the following examples, we assume that we are
currently matching the 2nd frame (Top:2, bottom:2). According to the match, a
'x' is placed above and below each matched fields.

With bottom matching (B<field>=I<bottom>):
	
	Match:           c         p           n          b          u
	
	                 x       x               x        x          x
	  Top          1 2 2     1 2 2       1 2 2      1 2 2      1 2 2
	  Bottom       1 2 3     1 2 3       1 2 3      1 2 3      1 2 3
	                 x         x           x        x              x
	
	Output frames:
	                 2          1          2          2          2
	                 2          2          2          1          3


With top matching (B<field>=I<top>):
	
	Match:           c         p           n          b          u
	
	                 x         x           x        x              x
	  Top          1 2 2     1 2 2       1 2 2      1 2 2      1 2 2
	  Bottom       1 2 3     1 2 3       1 2 3      1 2 3      1 2 3
	                 x       x               x        x          x
	
	Output frames:
	                 2          2          2          1          2
	                 2          1          3          2          2



=head3 Examples


Simple IVTC of a top field first telecined stream:
	
	fieldmatch=order=tff:combmatch=none, decimate


Advanced IVTC, with fallback on yadif for still combed frames:
	
	fieldmatch=order=tff:combmatch=full, yadif=deint=interlaced, decimate



=head2 fieldorder


Transform the field order of the input video.

This filter accepts the following options:


=over 4



=item B<order>

Output field order. Valid values are I<tff> for top field first or I<bff>
for bottom field first.

=back


Default value is B<tff>.

Transformation is achieved by shifting the picture content up or down
by one line, and filling the remaining line with appropriate picture content.
This method is consistent with most broadcast field order converters.

If the input video is not flagged as being interlaced, or it is already
flagged as being of the required output field order then this filter does
not alter the incoming video.

This filter is very useful when converting to or from PAL DV material,
which is bottom field first.

For example:
	
	ffmpeg -i in.vob -vf "fieldorder=bff" out.dv



=head2 fifo


Buffer input images and send them when they are requested.

This filter is mainly useful when auto-inserted by the libavfilter
framework.

The filter does not take parameters.



=head2 format


Convert the input video to one of the specified pixel formats.
Libavfilter will try to pick one that is supported for the input to
the next filter.

This filter accepts the following parameters:

=over 4



=item B<pix_fmts>

A '|'-separated list of pixel format names, for example
"pix_fmts=yuv420p|monow|rgb24".


=back



=head3 Examples



=over 4


=item *

Convert the input video to the format I<yuv420p>
	
	format=pix_fmts=yuv420p


Convert the input video to any of the formats in the list
	
	format=pix_fmts=yuv420p|yuv444p|yuv410p


=back



=head2 fps


Convert the video to specified constant frame rate by duplicating or dropping
frames as necessary.

This filter accepts the following named parameters:

=over 4



=item B<fps>

Desired output frame rate. The default is C<25>.


=item B<round>

Rounding method.

Possible values are:

=over 4


=item B<zero>

zero round towards 0

=item B<inf>

round away from 0

=item B<down>

round towards -infinity

=item B<up>

round towards +infinity

=item B<near>

round to nearest

=back

The default is C<near>.


=back


Alternatively, the options can be specified as a flat string:
I<fps>[:I<round>].

See also the setpts filter.


=head2 framestep


Select one frame every N-th frame.

This filter accepts the following option:

=over 4


=item B<step>

Select frame after every C<step> frames.
Allowed values are positive integers higher than 0. Default value is C<1>.

=back




=head2 frei0r


Apply a frei0r effect to the input video.

To enable compilation of this filter you need to install the frei0r
header and configure FFmpeg with C<--enable-frei0r>.

This filter accepts the following options:


=over 4



=item B<filter_name>

The name to the frei0r effect to load. If the environment variable
B<FREI0R_PATH> is defined, the frei0r effect is searched in each one of the
directories specified by the colon separated list in B<FREIOR_PATH>,
otherwise in the standard frei0r paths, which are in this order:
F<HOME/.frei0r-1/lib/>, F</usr/local/lib/frei0r-1/>,
F</usr/lib/frei0r-1/>.


=item B<filter_params>

A '|'-separated list of parameters to pass to the frei0r effect.


=back


A frei0r effect parameter can be a boolean (whose values are specified
with "y" and "n"), a double, a color (specified by the syntax
I<R>/I<G>/I<B>, I<R>, I<G>, and I<B> being float
numbers from 0.0 to 1.0) or by an C<av_parse_color()> color
description), a position (specified by the syntax I<X>/I<Y>,
I<X> and I<Y> being float numbers) and a string.

The number and kind of parameters depend on the loaded effect. If an
effect parameter is not specified the default value is set.


=head3 Examples



=over 4


=item *

Apply the distort0r effect, set the first two double parameters:
	
	frei0r=filter_name=distort0r:filter_params=0.5|0.01



=item *

Apply the colordistance effect, take a color as first parameter:
	
	frei0r=colordistance:0.2/0.3/0.4
	frei0r=colordistance:violet
	frei0r=colordistance:0x112233



=item *

Apply the perspective effect, specify the top left and top right image
positions:
	
	frei0r=perspective:0.2/0.2|0.8/0.2


=back


For more information see:
E<lt>B<http://frei0r.dyne.org>E<gt>


=head2 geq


The filter accepts the following options:


=over 4


=item B<lum_expr>

the luminance expression

=item B<cb_expr>

the chrominance blue expression

=item B<cr_expr>

the chrominance red expression

=item B<alpha_expr>

the alpha expression

=back


If one of the chrominance expression is not defined, it falls back on the other
one. If no alpha expression is specified it will evaluate to opaque value.
If none of chrominance expressions are
specified, they will evaluate the luminance expression.

The expressions can use the following variables and functions:


=over 4


=item B<N>

The sequential number of the filtered frame, starting from C<0>.


=item B<X>


=item B<Y>

The coordinates of the current sample.


=item B<W>


=item B<H>

The width and height of the image.


=item B<SW>


=item B<SH>

Width and height scale depending on the currently filtered plane. It is the
ratio between the corresponding luma plane number of pixels and the current
plane ones. E.g. for YUV4:2:0 the values are C<1,1> for the luma plane, and
C<0.5,0.5> for chroma planes.


=item B<T>

Time of the current frame, expressed in seconds.


=item B<p(x, y)>

Return the value of the pixel at location (I<x>,I<y>) of the current
plane.


=item B<lum(x, y)>

Return the value of the pixel at location (I<x>,I<y>) of the luminance
plane.


=item B<cb(x, y)>

Return the value of the pixel at location (I<x>,I<y>) of the
blue-difference chroma plane. Returns 0 if there is no such plane.


=item B<cr(x, y)>

Return the value of the pixel at location (I<x>,I<y>) of the
red-difference chroma plane. Returns 0 if there is no such plane.


=item B<alpha(x, y)>

Return the value of the pixel at location (I<x>,I<y>) of the alpha
plane. Returns 0 if there is no such plane.

=back


For functions, if I<x> and I<y> are outside the area, the value will be
automatically clipped to the closer edge.


=head3 Examples



=over 4


=item *

Flip the image horizontally:
	
	geq=p(W-X\,Y)



=item *

Generate a bidimensional sine wave, with angle C<PI/3> and a
wavelength of 100 pixels:
	
	geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128



=item *

Generate a fancy enigmatic moving light:
	
	nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128



=item *

Generate a quick emboss effect:
	
	format=gray,geq=lum_expr='(p(X,Y)+(256-p(X-4,Y-4)))/2'


=back



=head2 gradfun


Fix the banding artifacts that are sometimes introduced into nearly flat
regions by truncation to 8bit color depth.
Interpolate the gradients that should go where the bands are, and
dither them.

This filter is designed for playback only.  Do not use it prior to
lossy compression, because compression tends to lose the dither and
bring back the bands.

This filter accepts the following options:


=over 4



=item B<strength>

The maximum amount by which the filter will change any one pixel. Also the
threshold for detecting nearly flat regions. Acceptable values range from .51 to
64, default value is 1.2, out-of-range values will be clipped to the valid
range.


=item B<radius>

The neighborhood to fit the gradient to. A larger radius makes for smoother
gradients, but also prevents the filter from modifying the pixels near detailed
regions. Acceptable values are 8-32, default value is 16, out-of-range values
will be clipped to the valid range.


=back


Alternatively, the options can be specified as a flat string:
I<strength>[:I<radius>]


=head3 Examples



=over 4


=item *

Apply the filter with a C<3.5> strength and radius of C<8>:
	
	gradfun=3.5:8



=item *

Specify radius, omitting the strength (which will fall-back to the default
value):
	
	gradfun=radius=8



=back



=head2 hflip


Flip the input video horizontally.

For example to horizontally flip the input video with B<ffmpeg>:
	
	ffmpeg -i in.avi -vf "hflip" out.avi



=head2 histeq

This filter applies a global color histogram equalization on a
per-frame basis.

It can be used to correct video that has a compressed range of pixel
intensities.  The filter redistributes the pixel intensities to
equalize their distribution across the intensity range. It may be
viewed as an "automatically adjusting contrast filter". This filter is
useful only for correcting degraded or poorly captured source
video.

The filter accepts the following options:


=over 4


=item B<strength>

Determine the amount of equalization to be applied.  As the strength
is reduced, the distribution of pixel intensities more-and-more
approaches that of the input frame. The value must be a float number
in the range [0,1] and defaults to 0.200.


=item B<intensity>

Set the maximum intensity that can generated and scale the output
values appropriately.  The strength should be set as desired and then
the intensity can be limited if needed to avoid washing-out. The value
must be a float number in the range [0,1] and defaults to 0.210.


=item B<antibanding>

Set the antibanding level. If enabled the filter will randomly vary
the luminance of output pixels by a small amount to avoid banding of
the histogram. Possible values are C<none>, C<weak> or
C<strong>. It defaults to C<none>.

=back



=head2 histogram


Compute and draw a color distribution histogram for the input video.

The computed histogram is a representation of distribution of color components
in an image.

The filter accepts the following options:


=over 4


=item B<mode>

Set histogram mode.

It accepts the following values:

=over 4


=item B<levels>

standard histogram that display color components distribution in an image.
Displays color graph for each color component. Shows distribution
of the Y, U, V, A or G, B, R components, depending on input format,
in current frame. Bellow each graph is color component scale meter.


=item B<color>

chroma values in vectorscope, if brighter more such chroma values are
distributed in an image.
Displays chroma values (U/V color placement) in two dimensional graph
(which is called a vectorscope). It can be used to read of the hue and
saturation of the current frame. At a same time it is a histogram.
The whiter a pixel in the vectorscope, the more pixels of the input frame
correspond to that pixel (that is the more pixels have this chroma value).
The V component is displayed on the horizontal (X) axis, with the leftmost
side being V = 0 and the rightmost side being V = 255.
The U component is displayed on the vertical (Y) axis, with the top
representing U = 0 and the bottom representing U = 255.

The position of a white pixel in the graph corresponds to the chroma value
of a pixel of the input clip. So the graph can be used to read of the
hue (color flavor) and the saturation (the dominance of the hue in the color).
As the hue of a color changes, it moves around the square. At the center of
the square, the saturation is zero, which means that the corresponding pixel
has no color. If you increase the amount of a specific color, while leaving
the other colors unchanged, the saturation increases, and you move towards
the edge of the square.


=item B<color2>

chroma values in vectorscope, similar as C<color> but actual chroma values
are displayed.


=item B<waveform>

per row/column color component graph. In row mode graph in the left side represents
color component value 0 and right side represents value = 255. In column mode top
side represents color component value = 0 and bottom side represents value = 255.

=back

Default value is C<levels>.


=item B<level_height>

Set height of level in C<levels>. Default value is C<200>.
Allowed range is [50, 2048].


=item B<scale_height>

Set height of color scale in C<levels>. Default value is C<12>.
Allowed range is [0, 40].


=item B<step>

Set step for C<waveform> mode. Smaller values are useful to find out how much
of same luminance values across input rows/columns are distributed.
Default value is C<10>. Allowed range is [1, 255].


=item B<waveform_mode>

Set mode for C<waveform>. Can be either C<row>, or C<column>.
Default is C<row>.


=item B<display_mode>

Set display mode for C<waveform> and C<levels>.
It accepts the following values:

=over 4


=item B<parade>

Display separate graph for the color components side by side in
C<row> waveform mode or one below other in C<column> waveform mode
for C<waveform> histogram mode. For C<levels> histogram mode
per color component graphs are placed one bellow other.

This display mode in C<waveform> histogram mode makes it easy to spot
color casts in the highlights and shadows of an image, by comparing the
contours of the top and the bottom of each waveform.
Since whites, grays, and blacks are characterized by
exactly equal amounts of red, green, and blue, neutral areas of the
picture should display three waveforms of roughly equal width/height.
If not, the correction is easy to make by making adjustments to level the
three waveforms.


=item B<overlay>

Presents information that's identical to that in the C<parade>, except
that the graphs representing color components are superimposed directly
over one another.

This display mode in C<waveform> histogram mode can make it easier to spot
the relative differences or similarities in overlapping areas of the color
components that are supposed to be identical, such as neutral whites, grays,
or blacks.

=back

Default is C<parade>.

=back



=head3 Examples



=over 4



=item *

Calculate and draw histogram:
	
	ffplay -i input -vf histogram



=back



=head2 hqdn3d


High precision/quality 3d denoise filter. This filter aims to reduce
image noise producing smooth images and making still images really
still. It should enhance compressibility.

It accepts the following optional parameters:


=over 4


=item B<luma_spatial>

a non-negative float number which specifies spatial luma strength,
defaults to 4.0


=item B<chroma_spatial>

a non-negative float number which specifies spatial chroma strength,
defaults to 3.0*I<luma_spatial>/4.0


=item B<luma_tmp>

a float number which specifies luma temporal strength, defaults to
6.0*I<luma_spatial>/4.0


=item B<chroma_tmp>

a float number which specifies chroma temporal strength, defaults to
I<luma_tmp>*I<chroma_spatial>/I<luma_spatial>

=back



=head2 hue


Modify the hue and/or the saturation of the input.

This filter accepts the following options:


=over 4


=item B<h>

Specify the hue angle as a number of degrees. It accepts an expression,
and defaults to "0".


=item B<s>

Specify the saturation in the [-10,10] range. It accepts a float number and
defaults to "1".


=item B<H>

Specify the hue angle as a number of radians. It accepts a float
number or an expression, and defaults to "0".

=back


B<h> and B<H> are mutually exclusive, and can't be
specified at the same time.

The B<h>, B<H> and B<s> option values are
expressions containing the following constants:


=over 4


=item B<n>

frame count of the input frame starting from 0


=item B<pts>

presentation timestamp of the input frame expressed in time base units


=item B<r>

frame rate of the input video, NAN if the input frame rate is unknown


=item B<t>

timestamp expressed in seconds, NAN if the input timestamp is unknown


=item B<tb>

time base of the input video

=back



=head3 Examples



=over 4


=item *

Set the hue to 90 degrees and the saturation to 1.0:
	
	hue=h=90:s=1



=item *

Same command but expressing the hue in radians:
	
	hue=H=PI/2:s=1



=item *

Rotate hue and make the saturation swing between 0
and 2 over a period of 1 second:
	
	hue="H=2*PI*t: s=sin(2*PI*t)+1"



=item *

Apply a 3 seconds saturation fade-in effect starting at 0:
	
	hue="s=min(t/3\,1)"


The general fade-in expression can be written as:
	
	hue="s=min(0\, max((t-START)/DURATION\, 1))"



=item *

Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
	
	hue="s=max(0\, min(1\, (8-t)/3))"


The general fade-out expression can be written as:
	
	hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"



=back



=head3 Commands


This filter supports the following commands:

=over 4


=item B<s>


=item B<h>


=item B<H>

Modify the hue and/or the saturation of the input video.
The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current
value.

=back



=head2 idet


Detect video interlacing type.

This filter tries to detect if the input is interlaced or progressive,
top or bottom field first.

The filter accepts the following options:


=over 4


=item B<intl_thres>

Set interlacing threshold.

=item B<prog_thres>

Set progressive threshold.

=back



=head2 il


Deinterleave or interleave fields.

This filter allows to process interlaced images fields without
deinterlacing them. Deinterleaving splits the input frame into 2
fields (so called half pictures). Odd lines are moved to the top
half of the output image, even lines to the bottom half.
You can process (filter) them independently and then re-interleave them.

The filter accepts the following options:


=over 4


=item B<luma_mode, l>


=item B<chroma_mode, s>


=item B<alpha_mode, a>

Available values for I<luma_mode>, I<chroma_mode> and
I<alpha_mode> are:


=over 4


=item B<none>

Do nothing.


=item B<deinterleave, d>

Deinterleave fields, placing one above the other.


=item B<interleave, i>

Interleave fields. Reverse the effect of deinterleaving.

=back

Default value is C<none>.


=item B<luma_swap, ls>


=item B<chroma_swap, cs>


=item B<alpha_swap, as>

Swap luma/chroma/alpha fields. Exchange even & odd lines. Default value is C<0>.

=back



=head2 interlace


Simple interlacing filter from progressive contents. This interleaves upper (or
lower) lines from odd frames with lower (or upper) lines from even frames,
halving the frame rate and preserving image height.

	
	   Original        Original             New Frame
	   Frame 'j'      Frame 'j+1'             (tff)
	  ==========      ===========       ==================
	    Line 0  -------------------->    Frame 'j' Line 0
	    Line 1          Line 1  ---->   Frame 'j+1' Line 1
	    Line 2 --------------------->    Frame 'j' Line 2
	    Line 3          Line 3  ---->   Frame 'j+1' Line 3
	     ...             ...                   ...
	New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on


It accepts the following optional parameters:


=over 4


=item B<scan>

determines whether the interlaced frame is taken from the even (tff - default)
or odd (bff) lines of the progressive frame.


=item B<lowpass>

Enable (default) or disable the vertical lowpass filter to avoid twitter
interlacing and reduce moire patterns.

=back



=head2 kerndeint


Deinterlace input video by applying Donald Graft's adaptive kernel
deinterling. Work on interlaced parts of a video to produce
progressive frames.

The description of the accepted parameters follows.


=over 4


=item B<thresh>

Set the threshold which affects the filter's tolerance when
determining if a pixel line must be processed. It must be an integer
in the range [0,255] and defaults to 10. A value of 0 will result in
applying the process on every pixels.


=item B<map>

Paint pixels exceeding the threshold value to white if set to 1.
Default is 0.


=item B<order>

Set the fields order. Swap fields if set to 1, leave fields alone if
0. Default is 0.


=item B<sharp>

Enable additional sharpening if set to 1. Default is 0.


=item B<twoway>

Enable twoway sharpening if set to 1. Default is 0.

=back



=head3 Examples



=over 4


=item *

Apply default values:
	
	kerndeint=thresh=10:map=0:order=0:sharp=0:twoway=0



=item *

Enable additional sharpening:
	
	kerndeint=sharp=1



=item *

Paint processed pixels in white:
	
	kerndeint=map=1


=back



=head2 lut, lutrgb, lutyuv


Compute a look-up table for binding each pixel component input value
to an output value, and apply it to input video.

I<lutyuv> applies a lookup table to a YUV input video, I<lutrgb>
to an RGB input video.

These filters accept the following options:

=over 4


=item B<c0>

set first pixel component expression

=item B<c1>

set second pixel component expression

=item B<c2>

set third pixel component expression

=item B<c3>

set fourth pixel component expression, corresponds to the alpha component


=item B<r>

set red component expression

=item B<g>

set green component expression

=item B<b>

set blue component expression

=item B<a>

alpha component expression


=item B<y>

set Y/luminance component expression

=item B<u>

set U/Cb component expression

=item B<v>

set V/Cr component expression

=back


Each of them specifies the expression to use for computing the lookup table for
the corresponding pixel component values.

The exact component associated to each of the I<c*> options depends on the
format in input.

The I<lut> filter requires either YUV or RGB pixel formats in input,
I<lutrgb> requires RGB pixel formats in input, and I<lutyuv> requires YUV.

The expressions can contain the following constants and functions:


=over 4


=item B<w, h>

the input width and height


=item B<val>

input value for the pixel component


=item B<clipval>

the input value clipped in the I<minval>-I<maxval> range


=item B<maxval>

maximum value for the pixel component


=item B<minval>

minimum value for the pixel component


=item B<negval>

the negated value for the pixel component value clipped in the
I<minval>-I<maxval> range , it corresponds to the expression
"maxval-clipval+minval"


=item B<clip(val)>

the computed value in I<val> clipped in the
I<minval>-I<maxval> range


=item B<gammaval(gamma)>

the computed gamma correction value of the pixel component value
clipped in the I<minval>-I<maxval> range, corresponds to the
expression
"pow((clipval-minval)/(maxval-minval)\,I<gamma>)*(maxval-minval)+minval"


=back


All expressions default to "val".


=head3 Examples



=over 4


=item *

Negate input video:
	
	lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
	lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"


The above is the same as:
	
	lutrgb="r=negval:g=negval:b=negval"
	lutyuv="y=negval:u=negval:v=negval"



=item *

Negate luminance:
	
	lutyuv=y=negval



=item *

Remove chroma components, turns the video into a graytone image:
	
	lutyuv="u=128:v=128"



=item *

Apply a luma burning effect:
	
	lutyuv="y=2*val"



=item *

Remove green and blue components:
	
	lutrgb="g=0:b=0"



=item *

Set a constant alpha channel value on input:
	
	format=rgba,lutrgb=a="maxval-minval/2"



=item *

Correct luminance gamma by a 0.5 factor:
	
	lutyuv=y=gammaval(0.5)



=item *

Discard least significant bits of luma:
	
	lutyuv=y='bitand(val, 128+64+32)'


=back



=head2 mp


Apply an MPlayer filter to the input video.

This filter provides a wrapper around most of the filters of
MPlayer/MEncoder.

This wrapper is considered experimental. Some of the wrapped filters
may not work properly and we may drop support for them, as they will
be implemented natively into FFmpeg. Thus you should avoid
depending on them when writing portable scripts.

The filters accepts the parameters:
I<filter_name>[:=]I<filter_params>

I<filter_name> is the name of a supported MPlayer filter,
I<filter_params> is a string containing the parameters accepted by
the named filter.

The list of the currently supported filters follows:

=over 4


=item I<dint>


=item I<down3dright>


=item I<eq2>


=item I<eq>


=item I<fil>


=item I<fspp>


=item I<ilpack>


=item I<mcdeint>


=item I<ow>


=item I<perspective>


=item I<phase>


=item I<pp7>


=item I<pullup>


=item I<qp>


=item I<sab>


=item I<softpulldown>


=item I<spp>


=item I<tinterlace>


=item I<uspp>


=back


The parameter syntax and behavior for the listed filters are the same
of the corresponding MPlayer filters. For detailed instructions check
the "VIDEO FILTERS" section in the MPlayer manual.


=head3 Examples



=over 4


=item *

Adjust gamma, brightness, contrast:
	
	mp=eq2=1.0:2:0.5


=back


See also mplayer(1), E<lt>B<http://www.mplayerhq.hu/>E<gt>.


=head2 mpdecimate


Drop frames that do not differ greatly from the previous frame in
order to reduce frame rate.

The main use of this filter is for very-low-bitrate encoding
(e.g. streaming over dialup modem), but it could in theory be used for
fixing movies that were inverse-telecined incorrectly.

A description of the accepted options follows.


=over 4


=item B<max>

Set the maximum number of consecutive frames which can be dropped (if
positive), or the minimum interval between dropped frames (if
negative). If the value is 0, the frame is dropped unregarding the
number of previous sequentially dropped frames.

Default value is 0.


=item B<hi>


=item B<lo>


=item B<frac>

Set the dropping threshold values.

Values for B<hi> and B<lo> are for 8x8 pixel blocks and
represent actual pixel value differences, so a threshold of 64
corresponds to 1 unit of difference for each pixel, or the same spread
out differently over the block.

A frame is a candidate for dropping if no 8x8 blocks differ by more
than a threshold of B<hi>, and if no more than B<frac> blocks (1
meaning the whole image) differ by more than a threshold of B<lo>.

Default value for B<hi> is 64*12, default value for B<lo> is
64*5, and default value for B<frac> is 0.33.

=back




=head2 negate


Negate input video.

This filter accepts an integer in input, if non-zero it negates the
alpha component (if available). The default value in input is 0.


=head2 noformat


Force libavfilter not to use any of the specified pixel formats for the
input to the next filter.

This filter accepts the following parameters:

=over 4



=item B<pix_fmts>

A '|'-separated list of pixel format names, for example
"pix_fmts=yuv420p|monow|rgb24".


=back



=head3 Examples



=over 4


=item *

Force libavfilter to use a format different from I<yuv420p> for the
input to the vflip filter:
	
	noformat=pix_fmts=yuv420p,vflip



=item *

Convert the input video to any of the formats not contained in the list:
	
	noformat=yuv420p|yuv444p|yuv410p


=back



=head2 noise


Add noise on video input frame.

The filter accepts the following options:


=over 4


=item B<all_seed>


=item B<c0_seed>


=item B<c1_seed>


=item B<c2_seed>


=item B<c3_seed>

Set noise seed for specific pixel component or all pixel components in case
of I<all_seed>. Default value is C<123457>.


=item B<all_strength, alls>


=item B<c0_strength, c0s>


=item B<c1_strength, c1s>


=item B<c2_strength, c2s>


=item B<c3_strength, c3s>

Set noise strength for specific pixel component or all pixel components in case
I<all_strength>. Default value is C<0>. Allowed range is [0, 100].


=item B<all_flags, allf>


=item B<c0_flags, c0f>


=item B<c1_flags, c1f>


=item B<c2_flags, c2f>


=item B<c3_flags, c3f>

Set pixel component flags or set flags for all components if I<all_flags>.
Available values for component flags are:

=over 4


=item B<a>

averaged temporal noise (smoother)

=item B<p>

mix random noise with a (semi)regular pattern

=item B<q>

higher quality (slightly better looking, slightly slower)

=item B<t>

temporal noise (noise pattern changes between frames)

=item B<u>

uniform noise (gaussian otherwise)

=back


=back



=head3 Examples


Add temporal and uniform noise to input video:
	
	noise=alls=20:allf=t+u



=head2 null


Pass the video source unchanged to the output.


=head2 ocv


Apply video transform using libopencv.

To enable this filter install libopencv library and headers and
configure FFmpeg with C<--enable-libopencv>.

This filter accepts the following parameters:


=over 4



=item B<filter_name>

The name of the libopencv filter to apply.


=item B<filter_params>

The parameters to pass to the libopencv filter. If not specified the default
values are assumed.


=back


Refer to the official libopencv documentation for more precise
information:
E<lt>B<http://opencv.willowgarage.com/documentation/c/image_filtering.html>E<gt>

Follows the list of supported libopencv filters.



=head3 dilate


Dilate an image by using a specific structuring element.
This filter corresponds to the libopencv function C<cvDilate>.

It accepts the parameters: I<struct_el>|I<nb_iterations>.

I<struct_el> represents a structuring element, and has the syntax:
I<cols>xI<rows>+I<anchor_x>xI<anchor_y>/I<shape>

I<cols> and I<rows> represent the number of columns and rows of
the structuring element, I<anchor_x> and I<anchor_y> the anchor
point, and I<shape> the shape for the structuring element, and
can be one of the values "rect", "cross", "ellipse", "custom".

If the value for I<shape> is "custom", it must be followed by a
string of the form "=I<filename>". The file with name
I<filename> is assumed to represent a binary image, with each
printable character corresponding to a bright pixel. When a custom
I<shape> is used, I<cols> and I<rows> are ignored, the number
or columns and rows of the read file are assumed instead.

The default value for I<struct_el> is "3x3+0x0/rect".

I<nb_iterations> specifies the number of times the transform is
applied to the image, and defaults to 1.

Follow some example:
	
	# use the default values
	ocv=dilate
	
	# dilate using a structuring element with a 5x5 cross, iterate two times
	ocv=filter_name=dilate:filter_params=5x5+2x2/cross|2
	
	# read the shape from the file diamond.shape, iterate two times
	# the file diamond.shape may contain a pattern of characters like this:
	#   *
	#  ***
	# *****
	#  ***
	#   *
	# the specified cols and rows are ignored (but not the anchor point coordinates)
	ocv=dilate:0x0+2x2/custom=diamond.shape|2



=head3 erode


Erode an image by using a specific structuring element.
This filter corresponds to the libopencv function C<cvErode>.

The filter accepts the parameters: I<struct_el>:I<nb_iterations>,
with the same syntax and semantics as the dilate filter.


=head3 smooth


Smooth the input video.

The filter takes the following parameters:
I<type>|I<param1>|I<param2>|I<param3>|I<param4>.

I<type> is the type of smooth filter to apply, and can be one of
the following values: "blur", "blur_no_scale", "median", "gaussian",
"bilateral". The default value is "gaussian".

I<param1>, I<param2>, I<param3>, and I<param4> are
parameters whose meanings depend on smooth type. I<param1> and
I<param2> accept integer positive values or 0, I<param3> and
I<param4> accept float values.

The default value for I<param1> is 3, the default value for the
other parameters is 0.

These parameters correspond to the parameters assigned to the
libopencv function C<cvSmooth>.



=head2 overlay


Overlay one video on top of another.

It takes two inputs and one output, the first input is the "main"
video on which the second input is overlayed.

This filter accepts the following parameters:

A description of the accepted options follows.


=over 4


=item B<x>


=item B<y>

Set the expression for the x and y coordinates of the overlayed video
on the main video. Default value is "0" for both expressions. In case
the expression is invalid, it is set to a huge value (meaning that the
overlay will not be displayed within the output visible area).


=item B<enable>

Set the expression which enables the overlay. If the evaluation is
different from 0, the overlay is displayed on top of the input
frame. By default it is "1".


=item B<eval>

Set when the expressions for B<x>, B<y>, and
B<enable> are evaluated.

It accepts the following values:

=over 4


=item B<init>

only evaluate expressions once during the filter initialization or
when a command is processed


=item B<frame>

evaluate expressions for each incoming frame

=back


Default value is B<frame>.


=item B<shortest>

If set to 1, force the output to terminate when the shortest input
terminates. Default value is 0.


=item B<format>

Set the format for the output video.

It accepts the following values:

=over 4


=item B<yuv420>

force YUV420 output


=item B<yuv444>

force YUV444 output


=item B<rgb>

force RGB output

=back


Default value is B<yuv420>.


=item B<rgb> I<(deprecated)>

If set to 1, force the filter to accept inputs in the RGB
color space. Default value is 0. This option is deprecated, use
B<format> instead.


=item B<repeatlast>

If set to 1, force the filter to draw the last overlay frame over the
main input until the end of the stream. A value of 0 disables this
behavior, which is enabled by default.

=back


The B<x>, B<y>, and B<enable> expressions can
contain the following parameters.


=over 4


=item B<main_w, W>


=item B<main_h, H>

main input width and height


=item B<overlay_w, w>


=item B<overlay_h, h>

overlay input width and height


=item B<x>


=item B<y>

the computed values for I<x> and I<y>. They are evaluated for
each new frame.


=item B<hsub>


=item B<vsub>

horizontal and vertical chroma subsample values of the output
format. For example for the pixel format "yuv422p" I<hsub> is 2 and
I<vsub> is 1.


=item B<n>

the number of input frame, starting from 0


=item B<pos>

the position in the file of the input frame, NAN if unknown


=item B<t>

timestamp expressed in seconds, NAN if the input timestamp is unknown

=back


Note that the I<n>, I<pos>, I<t> variables are available only
when evaluation is done I<per frame>, and will evaluate to NAN
when B<eval> is set to B<init>.

Be aware that frames are taken from each input video in timestamp
order, hence, if their initial timestamps differ, it is a a good idea
to pass the two inputs through a I<setpts=PTS-STARTPTS> filter to
have them begin in the same zero timestamp, as it does the example for
the I<movie> filter.

You can chain together more overlays but you should test the
efficiency of such approach.


=head3 Commands


This filter supports the following commands:

=over 4


=item B<x>


=item B<y>


=item B<enable>

Modify the x/y and enable overlay of the overlay input.
The command accepts the same syntax of the corresponding option.

If the specified expression is not valid, it is kept at its current
value.

=back



=head3 Examples



=over 4


=item *

Draw the overlay at 10 pixels from the bottom right corner of the main
video:
	
	overlay=main_w-overlay_w-10:main_h-overlay_h-10


Using named options the example above becomes:
	
	overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10



=item *

Insert a transparent PNG logo in the bottom left corner of the input,
using the B<ffmpeg> tool with the C<-filter_complex> option:
	
	ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output



=item *

Insert 2 different transparent PNG logos (second logo on bottom
right corner) using the B<ffmpeg> tool:
	
	ffmpeg -i input -i logo1 -i logo2 -filter_complex 'overlay=x=10:y=H-h-10,overlay=x=W-w-10:y=H-h-10' output



=item *

Add a transparent color layer on top of the main video, C<WxH>
must specify the size of the main input to the overlay filter:
	
	color=color=red@.3:size=WxH [over]; [in][over] overlay [out]



=item *

Play an original video and a filtered version (here with the deshake
filter) side by side using the B<ffplay> tool:
	
	ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'


The above command is the same as:
	
	ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'



=item *

Make a sliding overlay appearing from the left to the right top part of the
screen starting since time 2:
	
	overlay=x='if(gte(t,2), -w+(t-2)*20, NAN)':y=0



=item *

Compose output by putting two input videos side to side:
	
	ffmpeg -i left.avi -i right.avi -filter_complex "
	nullsrc=size=200x100 [background];
	[0:v] setpts=PTS-STARTPTS, scale=100x100 [left];
	[1:v] setpts=PTS-STARTPTS, scale=100x100 [right];
	[background][left]       overlay=shortest=1       [background+left];
	[background+left][right] overlay=shortest=1:x=100 [left+right]
	"



=item *

Chain several overlays in cascade:
	
	nullsrc=s=200x200 [bg];
	testsrc=s=100x100, split=4 [in0][in1][in2][in3];
	[in0] lutrgb=r=0, [bg]   overlay=0:0     [mid0];
	[in1] lutrgb=g=0, [mid0] overlay=100:0   [mid1];
	[in2] lutrgb=b=0, [mid1] overlay=0:100   [mid2];
	[in3] null,       [mid2] overlay=100:100 [out0]



=back



=head2 pad


Add paddings to the input image, and place the original input at the
given coordinates I<x>, I<y>.

This filter accepts the following parameters:


=over 4


=item B<width, w>


=item B<height, h>

Specify an expression for the size of the output image with the
paddings added. If the value for I<width> or I<height> is 0, the
corresponding input size is used for the output.

The I<width> expression can reference the value set by the
I<height> expression, and vice versa.

The default value of I<width> and I<height> is 0.


=item B<x>


=item B<y>

Specify an expression for the offsets where to place the input image
in the padded area with respect to the top/left border of the output
image.

The I<x> expression can reference the value set by the I<y>
expression, and vice versa.

The default value of I<x> and I<y> is 0.


=item B<color>

Specify the color of the padded area, it can be the name of a color
(case insensitive match) or a 0xRRGGBB[AA] sequence.

The default value of I<color> is "black".

=back


The value for the I<width>, I<height>, I<x>, and I<y>
options are expressions containing the following constants:


=over 4


=item B<in_w, in_h>

the input video width and height


=item B<iw, ih>

same as I<in_w> and I<in_h>


=item B<out_w, out_h>

the output width and height, that is the size of the padded area as
specified by the I<width> and I<height> expressions


=item B<ow, oh>

same as I<out_w> and I<out_h>


=item B<x, y>

x and y offsets as specified by the I<x> and I<y>
expressions, or NAN if not yet specified


=item B<a>

same as I<iw> / I<ih>


=item B<sar>

input sample aspect ratio


=item B<dar>

input display aspect ratio, it is the same as (I<iw> / I<ih>) * I<sar>


=item B<hsub, vsub>

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" I<hsub> is 2 and I<vsub> is 1.

=back



=head3 Examples



=over 4


=item *

Add paddings with color "violet" to the input video. Output video
size is 640x480, the top-left corner of the input video is placed at
column 0, row 40:
	
	pad=640:480:0:40:violet


The example above is equivalent to the following command:
	
	pad=width=640:height=480:x=0:y=40:color=violet



=item *

Pad the input to get an output with dimensions increased by 3/2,
and put the input video at the center of the padded area:
	
	pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"



=item *

Pad the input to get a squared output with size equal to the maximum
value between the input width and height, and put the input video at
the center of the padded area:
	
	pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"



=item *

Pad the input to get a final w/h ratio of 16:9:
	
	pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"



=item *

In case of anamorphic video, in order to set the output display aspect
correctly, it is necessary to use I<sar> in the expression,
according to the relation:
	
	(ih * X / ih) * sar = output_dar
	X = output_dar / sar


Thus the previous example needs to be modified to:
	
	pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"



=item *

Double output size and put the input video in the bottom-right
corner of the output padded area:
	
	pad="2*iw:2*ih:ow-iw:oh-ih"


=back



=head2 pixdesctest


Pixel format descriptor test filter, mainly useful for internal
testing. The output video should be equal to the input video.

For example:
	
	format=monow, pixdesctest


can be used to test the monowhite pixel format descriptor definition.


=head2 pp


Enable the specified chain of postprocessing subfilters using libpostproc. This
library should be automatically selected with a GPL build (C<--enable-gpl>).
Subfilters must be separated by '/' and can be disabled by prepending a '-'.
Each subfilter and some options have a short and a long name that can be used
interchangeably, i.e. dr/dering are the same.

The filters accept the following options:


=over 4


=item B<subfilters>

Set postprocessing subfilters string.

=back


All subfilters share common options to determine their scope:


=over 4


=item B<a/autoq>

Honor the quality commands for this subfilter.


=item B<c/chrom>

Do chrominance filtering, too (default).


=item B<y/nochrom>

Do luminance filtering only (no chrominance).


=item B<n/noluma>

Do chrominance filtering only (no luminance).

=back


These options can be appended after the subfilter name, separated by a '|'.

Available subfilters are:


=over 4


=item B<hb/hdeblock[|difference[|flatness]]>

Horizontal deblocking filter

=over 4


=item B<difference>

Difference factor where higher values mean more deblocking (default: C<32>).

=item B<flatness>

Flatness threshold where lower values mean more deblocking (default: C<39>).

=back



=item B<vb/vdeblock[|difference[|flatness]]>

Vertical deblocking filter

=over 4


=item B<difference>

Difference factor where higher values mean more deblocking (default: C<32>).

=item B<flatness>

Flatness threshold where lower values mean more deblocking (default: C<39>).

=back



=item B<ha/hadeblock[|difference[|flatness]]>

Accurate horizontal deblocking filter

=over 4


=item B<difference>

Difference factor where higher values mean more deblocking (default: C<32>).

=item B<flatness>

Flatness threshold where lower values mean more deblocking (default: C<39>).

=back



=item B<va/vadeblock[|difference[|flatness]]>

Accurate vertical deblocking filter

=over 4


=item B<difference>

Difference factor where higher values mean more deblocking (default: C<32>).

=item B<flatness>

Flatness threshold where lower values mean more deblocking (default: C<39>).

=back


=back


The horizontal and vertical deblocking filters share the difference and
flatness values so you cannot set different horizontal and vertical
thresholds.


=over 4


=item B<h1/x1hdeblock>

Experimental horizontal deblocking filter


=item B<v1/x1vdeblock>

Experimental vertical deblocking filter


=item B<dr/dering>

Deringing filter


=item B<tn/tmpnoise[|threshold1[|threshold2[|threshold3]]], temporal noise reducer>


=over 4


=item B<threshold1>

larger -E<gt> stronger filtering

=item B<threshold2>

larger -E<gt> stronger filtering

=item B<threshold3>

larger -E<gt> stronger filtering

=back



=item B<al/autolevels[:f/fullyrange], automatic brightness / contrast correction>


=over 4


=item B<f/fullyrange>

Stretch luminance to C<0-255>.

=back



=item B<lb/linblenddeint>

Linear blend deinterlacing filter that deinterlaces the given block by
filtering all lines with a C<(1 2 1)> filter.


=item B<li/linipoldeint>

Linear interpolating deinterlacing filter that deinterlaces the given block by
linearly interpolating every second line.


=item B<ci/cubicipoldeint>

Cubic interpolating deinterlacing filter deinterlaces the given block by
cubically interpolating every second line.


=item B<md/mediandeint>

Median deinterlacing filter that deinterlaces the given block by applying a
median filter to every second line.


=item B<fd/ffmpegdeint>

FFmpeg deinterlacing filter that deinterlaces the given block by filtering every
second line with a C<(-1 4 2 4 -1)> filter.


=item B<l5/lowpass5>

Vertically applied FIR lowpass deinterlacing filter that deinterlaces the given
block by filtering all lines with a C<(-1 2 6 2 -1)> filter.


=item B<fq/forceQuant[|quantizer]>

Overrides the quantizer table from the input with the constant quantizer you
specify.

=over 4


=item B<quantizer>

Quantizer to use

=back



=item B<de/default>

Default pp filter combination (C<hb|a,vb|a,dr|a>)


=item B<fa/fast>

Fast pp filter combination (C<h1|a,v1|a,dr|a>)


=item B<ac>

High quality pp filter combination (C<ha|a|128|7,va|a,dr|a>)

=back



=head3 Examples



=over 4


=item *

Apply horizontal and vertical deblocking, deringing and automatic
brightness/contrast:
	
	pp=hb/vb/dr/al



=item *

Apply default filters without brightness/contrast correction:
	
	pp=de/-al



=item *

Apply default filters and temporal denoiser:
	
	pp=default/tmpnoise|1|2|3



=item *

Apply deblocking on luminance only, and switch vertical deblocking on or off
automatically depending on available CPU time:
	
	pp=hb|y/vb|a


=back



=head2 removelogo


Suppress a TV station logo, using an image file to determine which
pixels comprise the logo. It works by filling in the pixels that
comprise the logo with neighboring pixels.

The filters accept the following options:


=over 4


=item B<filename, f>

Set the filter bitmap file, which can be any image format supported by
libavformat. The width and height of the image file must match those of the
video stream being processed.

=back


Pixels in the provided bitmap image with a value of zero are not
considered part of the logo, non-zero pixels are considered part of
the logo. If you use white (255) for the logo and black (0) for the
rest, you will be safe. For making the filter bitmap, it is
recommended to take a screen capture of a black frame with the logo
visible, and then using a threshold filter followed by the erode
filter once or twice.

If needed, little splotches can be fixed manually. Remember that if
logo pixels are not covered, the filter quality will be much
reduced. Marking too many pixels as part of the logo does not hurt as
much, but it will increase the amount of blurring needed to cover over
the image and will destroy more information than necessary, and extra
pixels will slow things down on a large logo.


=head2 scale


Scale (resize) the input video, using the libswscale library.

The scale filter forces the output display aspect ratio to be the same
of the input, by changing the output sample aspect ratio.

The filter accepts the following options:


=over 4


=item B<width, w>

Output video width.
default value is C<iw>. See below
for the list of accepted constants.


=item B<height, h>

Output video height.
default value is C<ih>.
See below for the list of accepted constants.


=item B<interl>

Set the interlacing. It accepts the following values:


=over 4


=item B<1>

force interlaced aware scaling


=item B<0>

do not apply interlaced scaling


=item B<-1>

select interlaced aware scaling depending on whether the source frames
are flagged as interlaced or not

=back


Default value is C<0>.


=item B<flags>

Set libswscale scaling flags. If not explictly specified the filter
applies a bilinear scaling algorithm.


=item B<size, s>

Set the video size, the value must be a valid abbreviation or in the
form I<width>xI<height>.

=back


The values of the I<w> and I<h> options are expressions
containing the following constants:


=over 4


=item B<in_w, in_h>

the input width and height


=item B<iw, ih>

same as I<in_w> and I<in_h>


=item B<out_w, out_h>

the output (cropped) width and height


=item B<ow, oh>

same as I<out_w> and I<out_h>


=item B<a>

same as I<iw> / I<ih>


=item B<sar>

input sample aspect ratio


=item B<dar>

input display aspect ratio, it is the same as (I<iw> / I<ih>) * I<sar>


=item B<hsub, vsub>

horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" I<hsub> is 2 and I<vsub> is 1.

=back


If the input image format is different from the format requested by
the next filter, the scale filter will convert the input to the
requested format.

If the value for I<w> or I<h> is 0, the respective input
size is used for the output.

If the value for I<w> or I<h> is -1, the scale filter will use, for the
respective output size, a value that maintains the aspect ratio of the input
image.


=head3 Examples



=over 4


=item *

Scale the input video to a size of 200x100:
	
	scale=w=200:h=100


This is equivalent to:
	
	scale=w=200:h=100


or:
	
	scale=200x100



=item *

Specify a size abbreviation for the output size:
	
	scale=qcif


which can also be written as:
	
	scale=size=qcif



=item *

Scale the input to 2x:
	
	scale=w=2*iw:h=2*ih



=item *

The above is the same as:
	
	scale=2*in_w:2*in_h



=item *

Scale the input to 2x with forced interlaced scaling:
	
	scale=2*iw:2*ih:interl=1



=item *

Scale the input to half size:
	
	scale=w=iw/2:h=ih/2



=item *

Increase the width, and set the height to the same size:
	
	scale=3/2*iw:ow



=item *

Seek for Greek harmony:
	
	scale=iw:1/PHI*iw
	scale=ih*PHI:ih



=item *

Increase the height, and set the width to 3/2 of the height:
	
	scale=w=3/2*oh:h=3/5*ih



=item *

Increase the size, but make the size a multiple of the chroma
subsample values:
	
	scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"



=item *

Increase the width to a maximum of 500 pixels, keep the same input
aspect ratio:
	
	scale=w='min(500\, iw*3/2):h=-1'


=back



=head2 separatefields


The C<separatefields> takes a frame-based video input and splits
each frame into its components fields, producing a new half height clip
with twice the frame rate and twice the frame count.

This filter use field-dominance information in frame to decide which
of each pair of fields to place first in the output.
If it gets it wrong use setfield filter before C<separatefields> filter.


=head2 setdar, setsar


The C<setdar> filter sets the Display Aspect Ratio for the filter
output video.

This is done by changing the specified Sample (aka Pixel) Aspect
Ratio, according to the following equation:
	
	<DAR> = <HORIZONTAL_RESOLUTION> / <VERTICAL_RESOLUTION> * <SAR>


Keep in mind that the C<setdar> filter does not modify the pixel
dimensions of the video frame. Also the display aspect ratio set by
this filter may be changed by later filters in the filterchain,
e.g. in case of scaling or if another "setdar" or a "setsar" filter is
applied.

The C<setsar> filter sets the Sample (aka Pixel) Aspect Ratio for
the filter output video.

Note that as a consequence of the application of this filter, the
output display aspect ratio will change according to the equation
above.

Keep in mind that the sample aspect ratio set by the C<setsar>
filter may be changed by later filters in the filterchain, e.g. if
another "setsar" or a "setdar" filter is applied.

The filters accept the following options:


=over 4


=item B<r, ratio, dar (C<setdar> only), sar (C<setsar> only)>

Set the aspect ratio used by the filter.

The parameter can be a floating point number string, an expression, or
a string of the form I<num>:I<den>, where I<num> and
I<den> are the numerator and denominator of the aspect ratio. If
the parameter is not specified, it is assumed the value "0".
In case the form "I<num>:I<den>" is used, the C<:> character
should be escaped.


=item B<max>

Set the maximum integer value to use for expressing numerator and
denominator when reducing the expressed aspect ratio to a rational.
Default value is C<100>.


=back



=head3 Examples



=over 4



=item *

To change the display aspect ratio to 16:9, specify one of the following:
	
	setdar=dar=1.77777
	setdar=dar=16/9
	setdar=dar=1.77777



=item *

To change the sample aspect ratio to 10:11, specify:
	
	setsar=sar=10/11



=item *

To set a display aspect ratio of 16:9, and specify a maximum integer value of
1000 in the aspect ratio reduction, use the command:
	
	setdar=ratio=16/9:max=1000



=back




=head2 setfield


Force field for the output video frame.

The C<setfield> filter marks the interlace type field for the
output frames. It does not change the input frame, but only sets the
corresponding property, which affects how the frame is treated by
following filters (e.g. C<fieldorder> or C<yadif>).

The filter accepts the following options:


=over 4



=item B<mode>

Available values are:


=over 4


=item B<auto>

Keep the same field property.


=item B<bff>

Mark the frame as bottom-field-first.


=item B<tff>

Mark the frame as top-field-first.


=item B<prog>

Mark the frame as progressive.

=back


=back



=head2 showinfo


Show a line containing various information for each input video frame.
The input video is not modified.

The shown line contains a sequence of key/value pairs of the form
I<key>:I<value>.

A description of each shown parameter follows:


=over 4


=item B<n>

sequential number of the input frame, starting from 0


=item B<pts>

Presentation TimeStamp of the input frame, expressed as a number of
time base units. The time base unit depends on the filter input pad.


=item B<pts_time>

Presentation TimeStamp of the input frame, expressed as a number of
seconds


=item B<pos>

position of the frame in the input stream, -1 if this information in
unavailable and/or meaningless (for example in case of synthetic video)


=item B<fmt>

pixel format name


=item B<sar>

sample aspect ratio of the input frame, expressed in the form
I<num>/I<den>


=item B<s>

size of the input frame, expressed in the form
I<width>xI<height>


=item B<i>

interlaced mode ("P" for "progressive", "T" for top field first, "B"
for bottom field first)


=item B<iskey>

1 if the frame is a key frame, 0 otherwise


=item B<type>

picture type of the input frame ("I" for an I-frame, "P" for a
P-frame, "B" for a B-frame, "?" for unknown type).
Check also the documentation of the C<AVPictureType> enum and of
the C<av_get_picture_type_char> function defined in
F<libavutil/avutil.h>.


=item B<checksum>

Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame


=item B<plane_checksum>

Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
expressed in the form "[I<c0> I<c1> I<c2> I<c3>]"

=back



=head2 smartblur


Blur the input video without impacting the outlines.

The filter accepts the following options:


=over 4


=item B<luma_radius, lr>

Set the luma radius. The option value must be a float number in
the range [0.1,5.0] that specifies the variance of the gaussian filter
used to blur the image (slower if larger). Default value is 1.0.


=item B<luma_strength, ls>

Set the luma strength. The option value must be a float number
in the range [-1.0,1.0] that configures the blurring. A value included
in [0.0,1.0] will blur the image whereas a value included in
[-1.0,0.0] will sharpen the image. Default value is 1.0.


=item B<luma_threshold, lt>

Set the luma threshold used as a coefficient to determine
whether a pixel should be blurred or not. The option value must be an
integer in the range [-30,30]. A value of 0 will filter all the image,
a value included in [0,30] will filter flat areas and a value included
in [-30,0] will filter edges. Default value is 0.


=item B<chroma_radius, cr>

Set the chroma radius. The option value must be a float number in
the range [0.1,5.0] that specifies the variance of the gaussian filter
used to blur the image (slower if larger). Default value is 1.0.


=item B<chroma_strength, cs>

Set the chroma strength. The option value must be a float number
in the range [-1.0,1.0] that configures the blurring. A value included
in [0.0,1.0] will blur the image whereas a value included in
[-1.0,0.0] will sharpen the image. Default value is 1.0.


=item B<chroma_threshold, ct>

Set the chroma threshold used as a coefficient to determine
whether a pixel should be blurred or not. The option value must be an
integer in the range [-30,30]. A value of 0 will filter all the image,
a value included in [0,30] will filter flat areas and a value included
in [-30,0] will filter edges. Default value is 0.

=back


If a chroma option is not explicitly set, the corresponding luma value
is set.


=head2 stereo3d


Convert between different stereoscopic image formats.

The filters accept the following options:


=over 4


=item B<in>

Set stereoscopic image format of input.

Available values for input image formats are:

=over 4


=item B<sbsl>

side by side parallel (left eye left, right eye right)


=item B<sbsr>

side by side crosseye (right eye left, left eye right)


=item B<sbs2l>

side by side parallel with half width resolution
(left eye left, right eye right)


=item B<sbs2r>

side by side crosseye with half width resolution
(right eye left, left eye right)


=item B<abl>

above-below (left eye above, right eye below)


=item B<abr>

above-below (right eye above, left eye below)


=item B<ab2l>

above-below with half height resolution
(left eye above, right eye below)


=item B<ab2r>

above-below with half height resolution
(right eye above, left eye below)

Default value is B<sbsl>.

=back



=item B<out>

Set stereoscopic image format of output.

Available values for output image formats are all the input formats as well as:

=over 4


=item B<arbg>

anaglyph red/blue gray
(red filter on left eye, blue filter on right eye)


=item B<argg>

anaglyph red/green gray
(red filter on left eye, green filter on right eye)


=item B<arcg>

anaglyph red/cyan gray
(red filter on left eye, cyan filter on right eye)


=item B<arch>

anaglyph red/cyan half colored
(red filter on left eye, cyan filter on right eye)


=item B<arcc>

anaglyph red/cyan color
(red filter on left eye, cyan filter on right eye)


=item B<arcd>

anaglyph red/cyan color optimized with the least squares projection of dubois
(red filter on left eye, cyan filter on right eye)


=item B<agmg>

anaglyph green/magenta gray
(green filter on left eye, magenta filter on right eye)


=item B<agmh>

anaglyph green/magenta half colored
(green filter on left eye, magenta filter on right eye)


=item B<agmc>

anaglyph green/magenta colored
(green filter on left eye, magenta filter on right eye)


=item B<agmd>

anaglyph green/magenta color optimized with the least squares projection of dubois
(green filter on left eye, magenta filter on right eye)


=item B<aybg>

anaglyph yellow/blue gray
(yellow filter on left eye, blue filter on right eye)


=item B<aybh>

anaglyph yellow/blue half colored
(yellow filter on left eye, blue filter on right eye)


=item B<aybc>

anaglyph yellow/blue colored
(yellow filter on left eye, blue filter on right eye)


=item B<aybd>

anaglyph yellow/blue color optimized with the least squares projection of dubois
(yellow filter on left eye, blue filter on right eye)


=item B<irl>

interleaved rows (left eye has top row, right eye starts on next row)


=item B<irr>

interleaved rows (right eye has top row, left eye starts on next row)


=item B<ml>

mono output (left eye only)


=item B<mr>

mono output (right eye only)

=back


Default value is B<arcd>.

=back




=head2 subtitles


Draw subtitles on top of input video using the libass library.

To enable compilation of this filter you need to configure FFmpeg with
C<--enable-libass>. This filter also requires a build with libavcodec and
libavformat to convert the passed subtitles file to ASS (Advanced Substation
Alpha) subtitles format.

The filter accepts the following options:


=over 4


=item B<filename, f>

Set the filename of the subtitle file to read. It must be specified.


=item B<original_size>

Specify the size of the original video, the video for which the ASS file
was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
necessary to correctly scale the fonts if the aspect ratio has been changed.


=item B<charenc>

Set subtitles input character encoding. C<subtitles> filter only. Only
useful if not UTF-8.

=back


If the first key is not specified, it is assumed that the first value
specifies the B<filename>.

For example, to render the file F<sub.srt> on top of the input
video, use the command:
	
	subtitles=sub.srt


which is equivalent to:
	
	subtitles=filename=sub.srt



=head2 super2xsai


Scale the input by 2x and smooth using the Super2xSaI (Scale and
Interpolate) pixel art scaling algorithm.

Useful for enlarging pixel art images without reducing sharpness.


=head2 swapuv

Swap U & V plane.


=head2 telecine


Apply telecine process to the video.

This filter accepts the following options:


=over 4


=item B<first_field>


=over 4


=item B<top, t>

top field first

=item B<bottom, b>

bottom field first
The default value is C<top>.

=back



=item B<pattern>

A string of numbers representing the pulldown pattern you wish to apply.
The default value is C<23>.

=back


	
	Some typical patterns:
	
	NTSC output (30i):
	27.5p: 32222
	24p: 23 (classic)
	24p: 2332 (preferred)
	20p: 33
	18p: 334
	16p: 3444
	
	PAL output (25i):
	27.5p: 12222
	24p: 222222222223 ("Euro pulldown")
	16.67p: 33
	16p: 33333334



=head2 thumbnail

Select the most representative frame in a given sequence of consecutive frames.

The filter accepts the following options:


=over 4


=item B<n>

Set the frames batch size to analyze; in a set of I<n> frames, the filter
will pick one of them, and then handle the next batch of I<n> frames until
the end. Default is C<100>.

=back


Since the filter keeps track of the whole frames sequence, a bigger I<n>
value will result in a higher memory usage, so a high value is not recommended.


=head3 Examples



=over 4


=item *

Extract one picture each 50 frames:
	
	thumbnail=50



=item *

Complete example of a thumbnail creation with B<ffmpeg>:
	
	ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png


=back



=head2 tile


Tile several successive frames together.

The filter accepts the following options:


=over 4



=item B<layout>

Set the grid size (i.e. the number of lines and columns) in the form
"I<w>xI<h>".


=item B<nb_frames>

Set the maximum number of frames to render in the given area. It must be less
than or equal to I<w>xI<h>. The default value is C<0>, meaning all
the area will be used.


=item B<margin>

Set the outer border margin in pixels.


=item B<padding>

Set the inner border thickness (i.e. the number of pixels between frames). For
more advanced padding options (such as having different values for the edges),
refer to the pad video filter.


=back



=head3 Examples



=over 4


=item *

Produce 8x8 PNG tiles of all keyframes (B<-skip_frame nokey>) in a movie:
	
	ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png

The B<-vsync 0> is necessary to prevent B<ffmpeg> from
duplicating each output frame to accomodate the originally detected frame
rate.


=item *

Display C<5> pictures in an area of C<3x2> frames,
with C<7> pixels between them, and C<2> pixels of initial margin, using
mixed flat and named options:
	
	tile=3x2:nb_frames=5:padding=7:margin=2


=back



=head2 tinterlace


Perform various types of temporal field interlacing.

Frames are counted starting from 1, so the first input frame is
considered odd.

The filter accepts the following options:


=over 4



=item B<mode>

Specify the mode of the interlacing. This option can also be specified
as a value alone. See below for a list of values for this option.

Available values are:


=over 4


=item B<merge, 0>

Move odd frames into the upper field, even into the lower field,
generating a double height frame at half frame rate.


=item B<drop_odd, 1>

Only output even frames, odd frames are dropped, generating a frame with
unchanged height at half frame rate.


=item B<drop_even, 2>

Only output odd frames, even frames are dropped, generating a frame with
unchanged height at half frame rate.


=item B<pad, 3>

Expand each frame to full height, but pad alternate lines with black,
generating a frame with double height at the same input frame rate.


=item B<interleave_top, 4>

Interleave the upper field from odd frames with the lower field from
even frames, generating a frame with unchanged height at half frame rate.


=item B<interleave_bottom, 5>

Interleave the lower field from odd frames with the upper field from
even frames, generating a frame with unchanged height at half frame rate.


=item B<interlacex2, 6>

Double frame rate with unchanged height. Frames are inserted each
containing the second temporal field from the previous input frame and
the first temporal field from the next input frame. This mode relies on
the top_field_first flag. Useful for interlaced video displays with no
field synchronisation.

=back


Numeric values are deprecated but are accepted for backward
compatibility reasons.

Default mode is C<merge>.


=item B<flags>

Specify flags influencing the filter process.

Available value for I<flags> is:


=over 4


=item B<low_pass_filter, vlfp>

Enable vertical low-pass filtering in the filter.
Vertical low-pass filtering is required when creating an interlaced
destination from a progressive source which contains high-frequency
vertical detail. Filtering will reduce interlace 'twitter' and Moire
patterning.

Vertical low-pass filtering can only be enabled for B<mode>
I<interleave_top> and I<interleave_bottom>.


=back


=back



=head2 transpose


Transpose rows with columns in the input video and optionally flip it.

This filter accepts the following options:


=over 4



=item B<dir>

The direction of the transpose.


=over 4


=item B<0, 4, cclock_flip>

Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
	
	L.R     L.l
	. . ->  . .
	l.r     R.r



=item B<1, 5, clock>

Rotate by 90 degrees clockwise, that is:
	
	L.R     l.L
	. . ->  . .
	l.r     r.R



=item B<2, 6, cclock>

Rotate by 90 degrees counterclockwise, that is:
	
	L.R     R.r
	. . ->  . .
	l.r     L.l



=item B<3, 7, clock_flip>

Rotate by 90 degrees clockwise and vertically flip, that is:
	
	L.R     r.R
	. . ->  . .
	l.r     l.L


=back


For values between 4-7, the transposition is only done if the input
video geometry is portrait and not landscape. These values are
deprecated, the C<passthrough> option should be used instead.


=item B<passthrough>

Do not apply the transposition if the input geometry matches the one
specified by the specified value. It accepts the following values:

=over 4


=item B<none>

Always apply transposition.

=item B<portrait>

Preserve portrait geometry (when I<height> E<gt>= I<width>).

=item B<landscape>

Preserve landscape geometry (when I<width> E<gt>= I<height>).

=back


Default value is C<none>.

=back


For example to rotate by 90 degrees clockwise and preserve portrait
layout:
	
	transpose=dir=1:passthrough=portrait


The command above can also be specified as:
	
	transpose=1:portrait



=head2 unsharp


Sharpen or blur the input video.

It accepts the following parameters:


=over 4


=item B<luma_msize_x, lx>


=item B<chroma_msize_x, cx>

Set the luma/chroma matrix horizontal size. It must be an odd integer
between 3 and 63, default value is 5.


=item B<luma_msize_y, ly>


=item B<chroma_msize_y, cy>

Set the luma/chroma matrix vertical size. It must be an odd integer
between 3 and 63, default value is 5.


=item B<luma_amount, la>


=item B<chroma_amount, ca>

Set the luma/chroma effect strength. It can be a float number,
reasonable values lay between -1.5 and 1.5.

Negative values will blur the input video, while positive values will
sharpen it, a value of zero will disable the effect.

Default value is 1.0 for B<luma_amount>, 0.0 for
B<chroma_amount>.

=back


All parameters are optional and default to the
equivalent of the string '5:5:1.0:5:5:0.0'.


=head3 Examples



=over 4


=item *

Apply strong luma sharpen effect:
	
	unsharp=luma_msize_x=7:luma_msize_y=7:luma_amount=2.5



=item *

Apply strong blur of both luma and chroma parameters:
	
	unsharp=7:7:-2:7:7:-2


=back



=head2 vflip


Flip the input video vertically.

	
	ffmpeg -i in.avi -vf "vflip" out.avi




=head2 yadif


Deinterlace the input video ("yadif" means "yet another deinterlacing
filter").

This filter accepts the following options:



=over 4



=item B<mode>

The interlacing mode to adopt, accepts one of the following values:


=over 4


=item B<0, send_frame>

output 1 frame for each frame

=item B<1, send_field>

output 1 frame for each field

=item B<2, send_frame_nospatial>

like C<send_frame> but skip spatial interlacing check

=item B<3, send_field_nospatial>

like C<send_field> but skip spatial interlacing check

=back


Default value is C<send_frame>.


=item B<parity>

The picture field parity assumed for the input interlaced video, accepts one of
the following values:


=over 4


=item B<0, tff>

assume top field first

=item B<1, bff>

assume bottom field first

=item B<-1, auto>

enable automatic detection

=back


Default value is C<auto>.
If interlacing is unknown or decoder does not export this information,
top field first will be assumed.


=item B<deint>

Specify which frames to deinterlace. Accept one of the following
values:


=over 4


=item B<0, all>

deinterlace all frames

=item B<1, interlaced>

only deinterlace frames marked as interlaced

=back


Default value is C<all>.

=back




=head1 VIDEO SOURCES


Below is a description of the currently available video sources.


=head2 buffer


Buffer video frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular
through the interface defined in F<libavfilter/vsrc_buffer.h>.

This source accepts the following options:


=over 4



=item B<video_size>

Specify the size (width and height) of the buffered video frames.


=item B<width>

Input video width.


=item B<height>

Input video height.


=item B<pix_fmt>

A string representing the pixel format of the buffered video frames.
It may be a number corresponding to a pixel format, or a pixel format
name.


=item B<time_base>

Specify the timebase assumed by the timestamps of the buffered frames.


=item B<frame_rate>

Specify the frame rate expected for the video stream.


=item B<pixel_aspect, sar>

Specify the sample aspect ratio assumed by the video frames.


=item B<sws_param>

Specify the optional parameters to be used for the scale filter which
is automatically inserted when an input change is detected in the
input size or format.

=back


For example:
	
	buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=1


will instruct the source to accept video frames with size 320x240 and
with format "yuv410p", assuming 1/24 as the timestamps timebase and
square pixels (1:1 sample aspect ratio).
Since the pixel format with name "yuv410p" corresponds to the number 6
(check the enum AVPixelFormat definition in F<libavutil/pixfmt.h>),
this example corresponds to:
	
	buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1


Alternatively, the options can be specified as a flat string, but this
syntax is deprecated:

I<width>:I<height>:I<pix_fmt>:I<time_base.num>:I<time_base.den>:I<pixel_aspect.num>:I<pixel_aspect.den>[:I<sws_param>]


=head2 cellauto


Create a pattern generated by an elementary cellular automaton.

The initial state of the cellular automaton can be defined through the
B<filename>, and B<pattern> options. If such options are
not specified an initial state is created randomly.

At each new frame a new row in the video is filled with the result of
the cellular automaton next generation. The behavior when the whole
frame is filled is defined by the B<scroll> option.

This source accepts the following options:


=over 4


=item B<filename, f>

Read the initial cellular automaton state, i.e. the starting row, from
the specified file.
In the file, each non-whitespace character is considered an alive
cell, a newline will terminate the row, and further characters in the
file will be ignored.


=item B<pattern, p>

Read the initial cellular automaton state, i.e. the starting row, from
the specified string.

Each non-whitespace character in the string is considered an alive
cell, a newline will terminate the row, and further characters in the
string will be ignored.


=item B<rate, r>

Set the video rate, that is the number of frames generated per second.
Default is 25.


=item B<random_fill_ratio, ratio>

Set the random fill ratio for the initial cellular automaton row. It
is a floating point number value ranging from 0 to 1, defaults to
1/PHI.

This option is ignored when a file or a pattern is specified.


=item B<random_seed, seed>

Set the seed for filling randomly the initial row, must be an integer
included between 0 and UINT32_MAX. If not specified, or if explicitly
set to -1, the filter will try to use a good random seed on a best
effort basis.


=item B<rule>

Set the cellular automaton rule, it is a number ranging from 0 to 255.
Default value is 110.


=item B<size, s>

Set the size of the output video.

If B<filename> or B<pattern> is specified, the size is set
by default to the width of the specified initial state row, and the
height is set to I<width> * PHI.

If B<size> is set, it must contain the width of the specified
pattern string, and the specified pattern will be centered in the
larger row.

If a filename or a pattern string is not specified, the size value
defaults to "320x518" (used for a randomly generated initial state).


=item B<scroll>

If set to 1, scroll the output upward when all the rows in the output
have been already filled. If set to 0, the new generated row will be
written over the top row just after the bottom row is filled.
Defaults to 1.


=item B<start_full, full>

If set to 1, completely fill the output with generated rows before
outputting the first frame.
This is the default behavior, for disabling set the value to 0.


=item B<stitch>

If set to 1, stitch the left and right row edges together.
This is the default behavior, for disabling set the value to 0.

=back



=head3 Examples



=over 4


=item *

Read the initial state from F<pattern>, and specify an output of
size 200x400.
	
	cellauto=f=pattern:s=200x400



=item *

Generate a random initial row with a width of 200 cells, with a fill
ratio of 2/3:
	
	cellauto=ratio=2/3:s=200x200



=item *

Create a pattern generated by rule 18 starting by a single alive cell
centered on an initial row with width 100:
	
	cellauto=p=@s=100x400:full=0:rule=18



=item *

Specify a more elaborated initial pattern:
	
	cellauto=p='@@ @ @@':s=100x400:full=0:rule=18



=back



=head2 mandelbrot


Generate a Mandelbrot set fractal, and progressively zoom towards the
point specified with I<start_x> and I<start_y>.

This source accepts the following options:


=over 4



=item B<end_pts>

Set the terminal pts value. Default value is 400.


=item B<end_scale>

Set the terminal scale value.
Must be a floating point value. Default value is 0.3.


=item B<inner>

Set the inner coloring mode, that is the algorithm used to draw the
Mandelbrot fractal internal region.

It shall assume one of the following values:

=over 4


=item B<black>

Set black mode.

=item B<convergence>

Show time until convergence.

=item B<mincol>

Set color based on point closest to the origin of the iterations.

=item B<period>

Set period mode.

=back


Default value is I<mincol>.


=item B<bailout>

Set the bailout value. Default value is 10.0.


=item B<maxiter>

Set the maximum of iterations performed by the rendering
algorithm. Default value is 7189.


=item B<outer>

Set outer coloring mode.
It shall assume one of following values:

=over 4


=item B<iteration_count>

Set iteration cound mode.

=item B<normalized_iteration_count>

set normalized iteration count mode.

=back

Default value is I<normalized_iteration_count>.


=item B<rate, r>

Set frame rate, expressed as number of frames per second. Default
value is "25".


=item B<size, s>

Set frame size. Default value is "640x480".


=item B<start_scale>

Set the initial scale value. Default value is 3.0.


=item B<start_x>

Set the initial x position. Must be a floating point value between
-100 and 100. Default value is -0.743643887037158704752191506114774.


=item B<start_y>

Set the initial y position. Must be a floating point value between
-100 and 100. Default value is -0.131825904205311970493132056385139.

=back



=head2 mptestsrc


Generate various test patterns, as generated by the MPlayer test filter.

The size of the generated video is fixed, and is 256x256.
This source is useful in particular for testing encoding features.

This source accepts the following options:


=over 4



=item B<rate, r>

Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
I<frame_rate_num>/I<frame_rate_den>, an integer number, a float
number or a valid video frame rate abbreviation. The default value is
"25".


=item B<duration, d>

Set the video duration of the sourced video. The accepted syntax is:
	
	[-]HH:MM:SS[.m...]
	[-]S+[.m...]

See also the function C<av_parse_time()>.

If not specified, or the expressed duration is negative, the video is
supposed to be generated forever.


=item B<test, t>


Set the number or the name of the test to perform. Supported tests are:

=over 4


=item B<dc_luma>


=item B<dc_chroma>


=item B<freq_luma>


=item B<freq_chroma>


=item B<amp_luma>


=item B<amp_chroma>


=item B<cbp>


=item B<mv>


=item B<ring1>


=item B<ring2>


=item B<all>


=back


Default value is "all", which will cycle through the list of all tests.

=back


For example the following:
	
	testsrc=t=dc_luma


will generate a "dc_luma" test pattern.


=head2 frei0r_src


Provide a frei0r source.

To enable compilation of this filter you need to install the frei0r
header and configure FFmpeg with C<--enable-frei0r>.

This source accepts the following options:


=over 4



=item B<size>

The size of the video to generate, may be a string of the form
I<width>xI<height> or a frame size abbreviation.


=item B<framerate>

Framerate of the generated video, may be a string of the form
I<num>/I<den> or a frame rate abbreviation.


=item B<filter_name>

The name to the frei0r source to load. For more information regarding frei0r and
how to set the parameters read the section frei0r in the description of
the video filters.


=item B<filter_params>

A '|'-separated list of parameters to pass to the frei0r source.


=back


For example, to generate a frei0r partik0l source with size 200x200
and frame rate 10 which is overlayed on the overlay filter main input:
	
	frei0r_src=size=200x200:framerate=10:filter_name=partik0l:filter_params=1234 [overlay]; [in][overlay] overlay



=head2 life


Generate a life pattern.

This source is based on a generalization of John Conway's life game.

The sourced input represents a life grid, each pixel represents a cell
which can be in one of two possible states, alive or dead. Every cell
interacts with its eight neighbours, which are the cells that are
horizontally, vertically, or diagonally adjacent.

At each interaction the grid evolves according to the adopted rule,
which specifies the number of neighbor alive cells which will make a
cell stay alive or born. The B<rule> option allows to specify
the rule to adopt.

This source accepts the following options:


=over 4


=item B<filename, f>

Set the file from which to read the initial grid state. In the file,
each non-whitespace character is considered an alive cell, and newline
is used to delimit the end of each row.

If this option is not specified, the initial grid is generated
randomly.


=item B<rate, r>

Set the video rate, that is the number of frames generated per second.
Default is 25.


=item B<random_fill_ratio, ratio>

Set the random fill ratio for the initial random grid. It is a
floating point number value ranging from 0 to 1, defaults to 1/PHI.
It is ignored when a file is specified.


=item B<random_seed, seed>

Set the seed for filling the initial random grid, must be an integer
included between 0 and UINT32_MAX. If not specified, or if explicitly
set to -1, the filter will try to use a good random seed on a best
effort basis.


=item B<rule>

Set the life rule.

A rule can be specified with a code of the kind "SI<NS>/BI<NB>",
where I<NS> and I<NB> are sequences of numbers in the range 0-8,
I<NS> specifies the number of alive neighbor cells which make a
live cell stay alive, and I<NB> the number of alive neighbor cells
which make a dead cell to become alive (i.e. to "born").
"s" and "b" can be used in place of "S" and "B", respectively.

Alternatively a rule can be specified by an 18-bits integer. The 9
high order bits are used to encode the next cell state if it is alive
for each number of neighbor alive cells, the low order bits specify
the rule for "borning" new cells. Higher order bits encode for an
higher number of neighbor cells.
For example the number 6153 = C<(12E<lt>E<lt>9)+9> specifies a stay alive
rule of 12 and a born rule of 9, which corresponds to "S23/B03".

Default value is "S23/B3", which is the original Conway's game of life
rule, and will keep a cell alive if it has 2 or 3 neighbor alive
cells, and will born a new cell if there are three alive cells around
a dead cell.


=item B<size, s>

Set the size of the output video.

If B<filename> is specified, the size is set by default to the
same size of the input file. If B<size> is set, it must contain
the size specified in the input file, and the initial grid defined in
that file is centered in the larger resulting area.

If a filename is not specified, the size value defaults to "320x240"
(used for a randomly generated initial grid).


=item B<stitch>

If set to 1, stitch the left and right grid edges together, and the
top and bottom edges also. Defaults to 1.


=item B<mold>

Set cell mold speed. If set, a dead cell will go from B<death_color> to
B<mold_color> with a step of B<mold>. B<mold> can have a
value from 0 to 255.


=item B<life_color>

Set the color of living (or new born) cells.


=item B<death_color>

Set the color of dead cells. If B<mold> is set, this is the first color
used to represent a dead cell.


=item B<mold_color>

Set mold color, for definitely dead and moldy cells.

=back



=head3 Examples



=over 4


=item *

Read a grid from F<pattern>, and center it on a grid of size
300x300 pixels:
	
	life=f=pattern:s=300x300



=item *

Generate a random grid of size 200x200, with a fill ratio of 2/3:
	
	life=ratio=2/3:s=200x200



=item *

Specify a custom rule for evolving a randomly generated grid:
	
	life=rule=S14/B34



=item *

Full example with slow death effect (mold) using B<ffplay>:
	
	ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16


=back



=head2 color, nullsrc, rgbtestsrc, smptebars, smptehdbars, testsrc


The C<color> source provides an uniformly colored input.

The C<nullsrc> source returns unprocessed video frames. It is
mainly useful to be employed in analysis / debugging tools, or as the
source for filters which ignore the input data.

The C<rgbtestsrc> source generates an RGB test pattern useful for
detecting RGB vs BGR issues. You should see a red, green and blue
stripe from top to bottom.

The C<smptebars> source generates a color bars pattern, based on
the SMPTE Engineering Guideline EG 1-1990.

The C<smptehdbars> source generates a color bars pattern, based on
the SMPTE RP 219-2002.

The C<testsrc> source generates a test video pattern, showing a
color pattern, a scrolling gradient and a timestamp. This is mainly
intended for testing purposes.

The sources accept the following options:


=over 4



=item B<color, c>

Specify the color of the source, only used in the C<color>
source. It can be the name of a color (case insensitive match) or a
0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
default value is "black".


=item B<size, s>

Specify the size of the sourced video, it may be a string of the form
I<width>xI<height>, or the name of a size abbreviation. The
default value is "320x240".


=item B<rate, r>

Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
I<frame_rate_num>/I<frame_rate_den>, an integer number, a float
number or a valid video frame rate abbreviation. The default value is
"25".


=item B<sar>

Set the sample aspect ratio of the sourced video.


=item B<duration, d>

Set the video duration of the sourced video. The accepted syntax is:
	
	[-]HH[:MM[:SS[.m...]]]
	[-]S+[.m...]

See also the function C<av_parse_time()>.

If not specified, or the expressed duration is negative, the video is
supposed to be generated forever.


=item B<decimals, n>

Set the number of decimals to show in the timestamp, only used in the
C<testsrc> source.

The displayed timestamp value will correspond to the original
timestamp value multiplied by the power of 10 of the specified
value. Default value is 0.

=back


For example the following:
	
	testsrc=duration=5.3:size=qcif:rate=10


will generate a video with a duration of 5.3 seconds, with size
176x144 and a frame rate of 10 frames per second.

The following graph description will generate a red source
with an opacity of 0.2, with size "qcif" and a frame rate of 10
frames per second.
	
	color=c=red@0.2:s=qcif:r=10


If the input content is to be ignored, C<nullsrc> can be used. The
following command generates noise in the luminance plane by employing
the C<geq> filter:
	
	nullsrc=s=256x256, geq=random(1)*255:128:128




=head1 VIDEO SINKS


Below is a description of the currently available video sinks.


=head2 buffersink


Buffer video frames, and make them available to the end of the filter
graph.

This sink is mainly intended for a programmatic use, in particular
through the interface defined in F<libavfilter/buffersink.h>
or the options system.

It accepts a pointer to an AVBufferSinkContext structure, which
defines the incoming buffers' formats, to be passed as the opaque
parameter to C<avfilter_init_filter> for initialization.


=head2 nullsink


Null video sink, do absolutely nothing with the input video. It is
mainly useful as a template and to be employed in analysis / debugging
tools.



=head1 MULTIMEDIA FILTERS


Below is a description of the currently available multimedia filters.


=head2 aperms, perms


Set read/write permissions for the output frames.

These filters are mainly aimed at developers to test direct path in the
following filter in the filtergraph.

The filters accept the following options:


=over 4


=item B<mode>

Select the permissions mode.

It accepts the following values:

=over 4


=item B<none>

Do nothing. This is the default.

=item B<ro>

Set all the output frames read-only.

=item B<rw>

Set all the output frames directly writable.

=item B<toggle>

Make the frame read-only if writable, and writable if read-only.

=item B<random>

Set each output frame read-only or writable randomly.

=back



=item B<seed>

Set the seed for the I<random> mode, must be an integer included between
C<0> and C<UINT32_MAX>. If not specified, or if explicitly set to
C<-1>, the filter will try to use a good random seed on a best effort
basis.

=back


Note: in case of auto-inserted filter between the permission filter and the
following one, the permission might not be received as expected in that
following filter. Inserting a format or aformat filter before the
perms/aperms filter can avoid this problem.


=head2 aselect, select

Select frames to pass in output.

This filter accepts the following options:


=over 4



=item B<expr, e>

Set expression, which is evaluated for each input frame.

If the expression is evaluated to zero, the frame is discarded.

If the evaluation result is negative or NaN, the frame is sent to the
first output; otherwise it is sent to the output with index
C<ceil(val)-1>, assuming that the input index starts from 0.

For example a value of C<1.2> corresponds to the output with index
C<ceil(1.2)-1 = 2-1 = 1>, that is the second output.


=item B<outputs, n>

Set the number of outputs. The output to which to send the selected
frame is based on the result of the evaluation. Default value is 1.

=back


The expression can contain the following constants:


=over 4


=item B<n>

the sequential number of the filtered frame, starting from 0


=item B<selected_n>

the sequential number of the selected frame, starting from 0


=item B<prev_selected_n>

the sequential number of the last selected frame, NAN if undefined


=item B<TB>

timebase of the input timestamps


=item B<pts>

the PTS (Presentation TimeStamp) of the filtered video frame,
expressed in I<TB> units, NAN if undefined


=item B<t>

the PTS (Presentation TimeStamp) of the filtered video frame,
expressed in seconds, NAN if undefined


=item B<prev_pts>

the PTS of the previously filtered video frame, NAN if undefined


=item B<prev_selected_pts>

the PTS of the last previously filtered video frame, NAN if undefined


=item B<prev_selected_t>

the PTS of the last previously selected video frame, NAN if undefined


=item B<start_pts>

the PTS of the first video frame in the video, NAN if undefined


=item B<start_t>

the time of the first video frame in the video, NAN if undefined


=item B<pict_type> I<(video only)>

the type of the filtered frame, can assume one of the following
values:

=over 4


=item B<I>


=item B<P>


=item B<B>


=item B<S>


=item B<SI>


=item B<SP>


=item B<BI>


=back



=item B<interlace_type> I<(video only)>

the frame interlace type, can assume one of the following values:

=over 4


=item B<PROGRESSIVE>

the frame is progressive (not interlaced)

=item B<TOPFIRST>

the frame is top-field-first

=item B<BOTTOMFIRST>

the frame is bottom-field-first

=back



=item B<consumed_sample_n> I<(audio only)>

the number of selected samples before the current frame


=item B<samples_n> I<(audio only)>

the number of samples in the current frame


=item B<sample_rate> I<(audio only)>

the input sample rate


=item B<key>

1 if the filtered frame is a key-frame, 0 otherwise


=item B<pos>

the position in the file of the filtered frame, -1 if the information
is not available (e.g. for synthetic video)


=item B<scene> I<(video only)>

value between 0 and 1 to indicate a new scene; a low value reflects a low
probability for the current frame to introduce a new scene, while a higher
value means the current frame is more likely to be one (see the example below)


=back


The default value of the select expression is "1".


=head3 Examples



=over 4


=item *

Select all frames in input:
	
	select


The example above is the same as:
	
	select=1



=item *

Skip all frames:
	
	select=0



=item *

Select only I-frames:
	
	select='eq(pict_type\,I)'



=item *

Select one frame every 100:
	
	select='not(mod(n\,100))'



=item *

Select only frames contained in the 10-20 time interval:
	
	select='gte(t\,10)*lte(t\,20)'



=item *

Select only I frames contained in the 10-20 time interval:
	
	select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'



=item *

Select frames with a minimum distance of 10 seconds:
	
	select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'



=item *

Use aselect to select only audio frames with samples number E<gt> 100:
	
	aselect='gt(samples_n\,100)'



=item *

Create a mosaic of the first scenes:
	
	ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png


Comparing I<scene> against a value between 0.3 and 0.5 is generally a sane
choice.


=item *

Send even and odd frames to separate outputs, and compose them:
	
	select=n=2:e='mod(n, 2)+1' [odd][even]; [odd] pad=h=2*ih [tmp]; [tmp][even] overlay=y=h


=back



=head2 asendcmd, sendcmd


Send commands to filters in the filtergraph.

These filters read commands to be sent to other filters in the
filtergraph.

C<asendcmd> must be inserted between two audio filters,
C<sendcmd> must be inserted between two video filters, but apart
from that they act the same way.

The specification of commands can be provided in the filter arguments
with the I<commands> option, or in a file specified by the
I<filename> option.

These filters accept the following options:

=over 4


=item B<commands, c>

Set the commands to be read and sent to the other filters.

=item B<filename, f>

Set the filename of the commands to be read and sent to the other
filters.

=back



=head3 Commands syntax


A commands description consists of a sequence of interval
specifications, comprising a list of commands to be executed when a
particular event related to that interval occurs. The occurring event
is typically the current frame time entering or leaving a given time
interval.

An interval is specified by the following syntax:
	
	<START>[-<END>] <COMMANDS>;


The time interval is specified by the I<START> and I<END> times.
I<END> is optional and defaults to the maximum time.

The current frame time is considered within the specified interval if
it is included in the interval [I<START>, I<END>), that is when
the time is greater or equal to I<START> and is lesser than
I<END>.

I<COMMANDS> consists of a sequence of one or more command
specifications, separated by ",", relating to that interval.  The
syntax of a command specification is given by:
	
	[<FLAGS>] <TARGET> <COMMAND> <ARG>


I<FLAGS> is optional and specifies the type of events relating to
the time interval which enable sending the specified command, and must
be a non-null sequence of identifier flags separated by "+" or "|" and
enclosed between "[" and "]".

The following flags are recognized:

=over 4


=item B<enter>

The command is sent when the current frame timestamp enters the
specified interval. In other words, the command is sent when the
previous frame timestamp was not in the given interval, and the
current is.


=item B<leave>

The command is sent when the current frame timestamp leaves the
specified interval. In other words, the command is sent when the
previous frame timestamp was in the given interval, and the
current is not.

=back


If I<FLAGS> is not specified, a default value of C<[enter]> is
assumed.

I<TARGET> specifies the target of the command, usually the name of
the filter class or a specific filter instance name.

I<COMMAND> specifies the name of the command for the target filter.

I<ARG> is optional and specifies the optional list of argument for
the given I<COMMAND>.

Between one interval specification and another, whitespaces, or
sequences of characters starting with C<#> until the end of line,
are ignored and can be used to annotate comments.

A simplified BNF description of the commands specification syntax
follows:
	
	<COMMAND_FLAG>  ::= "enter" | "leave"
	<COMMAND_FLAGS> ::= <COMMAND_FLAG> [(+|"|")<COMMAND_FLAG>]
	<COMMAND>       ::= ["[" <COMMAND_FLAGS> "]"] <TARGET> <COMMAND> [<ARG>]
	<COMMANDS>      ::= <COMMAND> [,<COMMANDS>]
	<INTERVAL>      ::= <START>[-<END>] <COMMANDS>
	<INTERVALS>     ::= <INTERVAL>[;<INTERVALS>]



=head3 Examples



=over 4


=item *

Specify audio tempo change at second 4:
	
	asendcmd=c='4.0 atempo tempo 1.5',atempo



=item *

Specify a list of drawtext and hue commands in a file.
	
	# show text in the interval 5-10
	5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
	         [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
	
	# desaturate the image in the interval 15-20
	15.0-20.0 [enter] hue s 0,
	          [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
	          [leave] hue s 1,
	          [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
	
	# apply an exponential saturation fade-out effect, starting from time 25
	25 [enter] hue s exp(25-t)


A filtergraph allowing to read and process the above command list
stored in a file F<test.cmd>, can be specified with:
	
	sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue


=back




=head2 asetpts, setpts


Change the PTS (presentation timestamp) of the input frames.

C<asetpts> works on audio frames, C<setpts> on video frames.

This filter accepts the following options:


=over 4



=item B<expr>

The expression which is evaluated for each frame to construct its timestamp.


=back


The expression is evaluated through the eval API and can contain the following
constants:


=over 4


=item B<FRAME_RATE>

frame rate, only defined for constant frame-rate video


=item B<PTS>

the presentation timestamp in input


=item B<N>

the count of the input frame, starting from 0.


=item B<NB_CONSUMED_SAMPLES>

the number of consumed samples, not including the current frame (only
audio)


=item B<NB_SAMPLES>

the number of samples in the current frame (only audio)


=item B<SAMPLE_RATE>

audio sample rate


=item B<STARTPTS>

the PTS of the first frame


=item B<STARTT>

the time in seconds of the first frame


=item B<INTERLACED>

tell if the current frame is interlaced


=item B<T>

the time in seconds of the current frame


=item B<TB>

the time base


=item B<POS>

original position in the file of the frame, or undefined if undefined
for the current frame


=item B<PREV_INPTS>

previous input PTS


=item B<PREV_INT>

previous input time in seconds


=item B<PREV_OUTPTS>

previous output PTS


=item B<PREV_OUTT>

previous output time in seconds


=item B<RTCTIME>

wallclock (RTC) time in microseconds. This is deprecated, use time(0)
instead.


=item B<RTCSTART>

wallclock (RTC) time at the start of the movie in microseconds

=back



=head3 Examples



=over 4


=item *

Start counting PTS from zero
	
	setpts=PTS-STARTPTS



=item *

Apply fast motion effect:
	
	setpts=0.5*PTS



=item *

Apply slow motion effect:
	
	setpts=2.0*PTS



=item *

Set fixed rate of 25 frames per second:
	
	setpts=N/(25*TB)



=item *

Set fixed rate 25 fps with some jitter:
	
	setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'



=item *

Apply an offset of 10 seconds to the input PTS:
	
	setpts=PTS+10/TB



=item *

Generate timestamps from a "live source" and rebase onto the current timebase:
	
	setpts='(RTCTIME - RTCSTART) / (TB * 1000000)'


=back



=head2 ebur128


EBU R128 scanner filter. This filter takes an audio stream as input and outputs
it unchanged. By default, it logs a message at a frequency of 10Hz with the
Momentary loudness (identified by C<M>), Short-term loudness (C<S>),
Integrated loudness (C<I>) and Loudness Range (C<LRA>).

The filter also has a video output (see the I<video> option) with a real
time graph to observe the loudness evolution. The graphic contains the logged
message mentioned above, so it is not printed anymore when this option is set,
unless the verbose logging is set. The main graphing area contains the
short-term loudness (3 seconds of analysis), and the gauge on the right is for
the momentary loudness (400 milliseconds).

More information about the Loudness Recommendation EBU R128 on
E<lt>B<http://tech.ebu.ch/loudness>E<gt>.

The filter accepts the following options:


=over 4



=item B<video>

Activate the video output. The audio stream is passed unchanged whether this
option is set or no. The video stream will be the first output stream if
activated. Default is C<0>.


=item B<size>

Set the video size. This option is for video only. Default and minimum
resolution is C<640x480>.


=item B<meter>

Set the EBU scale meter. Default is C<9>. Common values are C<9> and
C<18>, respectively for EBU scale meter +9 and EBU scale meter +18. Any
other integer value between this range is allowed.


=item B<metadata>

Set metadata injection. If set to C<1>, the audio input will be segmented
into 100ms output frames, each of them containing various loudness information
in metadata.  All the metadata keys are prefixed with C<lavfi.r128.>.

Default is C<0>.


=item B<framelog>

Force the frame logging level.

Available values are:

=over 4


=item B<info>

information logging level

=item B<verbose>

verbose logging level

=back


By default, the logging level is set to I<info>. If the B<video> or
the B<metadata> options are set, it switches to I<verbose>.

=back



=head3 Examples



=over 4


=item *

Real-time graph using B<ffplay>, with a EBU scale meter +18:
	
	ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"



=item *

Run an analysis with B<ffmpeg>:
	
	ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -


=back



=head2 settb, asettb


Set the timebase to use for the output frames timestamps.
It is mainly useful for testing timebase configuration.

This filter accepts the following options:


=over 4



=item B<expr, tb>

The expression which is evaluated into the output timebase.


=back


The value for B<tb> is an arithmetic expression representing a
rational. The expression can contain the constants "AVTB" (the default
timebase), "intb" (the input timebase) and "sr" (the sample rate,
audio only). Default value is "intb".


=head3 Examples



=over 4


=item *

Set the timebase to 1/25:
	
	settb=expr=1/25



=item *

Set the timebase to 1/10:
	
	settb=expr=0.1



=item *

Set the timebase to 1001/1000:
	
	settb=1+0.001



=item *

Set the timebase to 2*intb:
	
	settb=2*intb



=item *

Set the default timebase value:
	
	settb=AVTB


=back



=head2 concat


Concatenate audio and video streams, joining them together one after the
other.

The filter works on segments of synchronized video and audio streams. All
segments must have the same number of streams of each type, and that will
also be the number of streams at output.

The filter accepts the following options:


=over 4



=item B<n>

Set the number of segments. Default is 2.


=item B<v>

Set the number of output video streams, that is also the number of video
streams in each segment. Default is 1.


=item B<a>

Set the number of output audio streams, that is also the number of video
streams in each segment. Default is 0.


=item B<unsafe>

Activate unsafe mode: do not fail if segments have a different format.


=back


The filter has I<v>+I<a> outputs: first I<v> video outputs, then
I<a> audio outputs.

There are I<n>x(I<v>+I<a>) inputs: first the inputs for the first
segment, in the same order as the outputs, then the inputs for the second
segment, etc.

Related streams do not always have exactly the same duration, for various
reasons including codec frame size or sloppy authoring. For that reason,
related synchronized streams (e.g. a video and its audio track) should be
concatenated at once. The concat filter will use the duration of the longest
stream in each segment (except the last one), and if necessary pad shorter
audio streams with silence.

For this filter to work correctly, all segments must start at timestamp 0.

All corresponding streams must have the same parameters in all segments; the
filtering system will automatically select a common pixel format for video
streams, and a common sample format, sample rate and channel layout for
audio streams, but other settings, such as resolution, must be converted
explicitly by the user.

Different frame rates are acceptable but will result in variable frame rate
at output; be sure to configure the output file to handle it.


=head3 Examples



=over 4


=item *

Concatenate an opening, an episode and an ending, all in bilingual version
(video in stream 0, audio in streams 1 and 2):
	
	ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
	  '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
	   concat=n=3:v=1:a=2 [v] [a1] [a2]' \
	  -map '[v]' -map '[a1]' -map '[a2]' output.mkv



=item *

Concatenate two parts, handling audio and video separately, using the
(a)movie sources, and adjusting the resolution:
	
	movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
	movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
	[v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]

Note that a desync will happen at the stitch if the audio and video streams
do not have exactly the same duration in the first file.


=back



=head2 showspectrum


Convert input audio to a video output, representing the audio frequency
spectrum.

The filter accepts the following options:


=over 4


=item B<size, s>

Specify the video size for the output. Default value is C<640x512>.


=item B<slide>

Specify if the spectrum should slide along the window. Default value is
C<0>.


=item B<mode>

Specify display mode.

It accepts the following values:

=over 4


=item B<combined>

all channels are displayed in the same row

=item B<separate>

all channels are displayed in separate rows

=back


Default value is B<combined>.


=item B<color>

Specify display color mode.

It accepts the following values:

=over 4


=item B<channel>

each channel is displayed in a separate color

=item B<intensity>

each channel is is displayed using the same color scheme

=back


Default value is B<channel>.


=item B<scale>

Specify scale used for calculating intensity color values.

It accepts the following values:

=over 4


=item B<lin>

linear

=item B<sqrt>

square root, default

=item B<cbrt>

cubic root

=item B<log>

logarithmic

=back


Default value is B<sqrt>.


=item B<saturation>

Set saturation modifier for displayed colors. Negative values provide
alternative color scheme. C<0> is no saturation at all.
Saturation must be in [-10.0, 10.0] range.
Default value is C<1>.

=back


The usage is very similar to the showwaves filter; see the examples in that
section.


=head3 Examples



=over 4


=item *

Large window with logarithmic color scaling:
	
	showspectrum=s=1280x480:scale=log



=item *

Complete example for a colored and sliding spectrum per channel using B<ffplay>:
	
	ffplay -f lavfi 'amovie=input.mp3, asplit [a][out1];
	             [a] showspectrum=mode=separate:color=intensity:slide=1:scale=cbrt [out0]'


=back



=head2 showwaves


Convert input audio to a video output, representing the samples waves.

The filter accepts the following options:


=over 4


=item B<size, s>

Specify the video size for the output. Default value is "600x240".


=item B<mode>

Set display mode.

Available values are:

=over 4


=item B<point>

Draw a point for each sample.


=item B<line>

Draw a vertical line for each sample.

=back


Default value is C<point>.


=item B<n>

Set the number of samples which are printed on the same column. A
larger value will decrease the frame rate. Must be a positive
integer. This option can be set only if the value for I<rate>
is not explicitly specified.


=item B<rate, r>

Set the (approximate) output frame rate. This is done by setting the
option I<n>. Default value is "25".


=back



=head3 Examples



=over 4


=item *

Output the input file audio and the corresponding video representation
at the same time:
	
	amovie=a.mp3,asplit[out0],showwaves[out1]



=item *

Create a synthetic signal and show it with showwaves, forcing a
frame rate of 30 frames per second:
	
	aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]


=back



=head2 split, asplit


Split input into several identical outputs.

C<asplit> works with audio input, C<split> with video.

The filter accepts a single parameter which specifies the number of outputs. If
unspecified, it defaults to 2.


=head3 Examples



=over 4


=item *

Create two separate outputs from the same input:
	
	[in] split [out0][out1]



=item *

To create 3 or more outputs, you need to specify the number of
outputs, like in:
	
	[in] asplit=3 [out0][out1][out2]



=item *

Create two separate outputs from the same input, one cropped and
one padded:
	
	[in] split [splitout1][splitout2];
	[splitout1] crop=100:100:0:0    [cropout];
	[splitout2] pad=200:200:100:100 [padout];



=item *

Create 5 copies of the input audio with B<ffmpeg>:
	
	ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT


=back




=head1 MULTIMEDIA SOURCES


Below is a description of the currently available multimedia sources.


=head2 amovie


This is the same as movie source, except it selects an audio
stream by default.



=head2 movie


Read audio and/or video stream(s) from a movie container.

This filter accepts the following options:


=over 4


=item B<filename>

The name of the resource to read (not necessarily a file but also a device or a
stream accessed through some protocol).


=item B<format_name, f>

Specifies the format assumed for the movie to read, and can be either
the name of a container or an input device. If not specified the
format is guessed from I<movie_name> or by probing.


=item B<seek_point, sp>

Specifies the seek point in seconds, the frames will be output
starting from this seek point, the parameter is evaluated with
C<av_strtod> so the numerical value may be suffixed by an IS
postfix. Default value is "0".


=item B<streams, s>

Specifies the streams to read. Several streams can be specified,
separated by "+". The source will then have as many outputs, in the
same order. The syntax is explained in the ``Stream specifiers''
section in the ffmpeg manual. Two special names, "dv" and "da" specify
respectively the default (best suited) video and audio stream. Default
is "dv", or "da" if the filter is called as "amovie".


=item B<stream_index, si>

Specifies the index of the video stream to read. If the value is -1,
the best suited video stream will be automatically selected. Default
value is "-1". Deprecated. If the filter is called "amovie", it will select
audio instead of video.


=item B<loop>

Specifies how many times to read the stream in sequence.
If the value is less than 1, the stream will be read again and again.
Default value is "1".

Note that when the movie is looped the source timestamps are not
changed, so it will generate non monotonically increasing timestamps.

=back


This filter allows to overlay a second video on top of main input of
a filtergraph as shown in this graph:
	
	input -----------> deltapts0 --> overlay --> output
	                                    ^
	                                    |
	movie --> scale--> deltapts1 -------+



=head3 Examples



=over 4


=item *

Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
on top of the input labelled as "in":
	
	movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [over];
	[in] setpts=PTS-STARTPTS [main];
	[main][over] overlay=16:16 [out]



=item *

Read from a video4linux2 device, and overlay it on top of the input
labelled as "in":
	
	movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [over];
	[in] setpts=PTS-STARTPTS [main];
	[main][over] overlay=16:16 [out]



=item *

Read the first video stream and the audio stream with id 0x81 from
dvd.vob; the video is connected to the pad named "video" and the audio is
connected to the pad named "audio":
	
	movie=dvd.vob:s=v:0+#0x81 [video] [audio]


=back




=head1 SEE ALSO



ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libavfilter(3)


=head1 AUTHORS


The FFmpeg developers.

For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
B<git log> in the FFmpeg source directory, or browsing the
online repository at E<lt>B<http://source.ffmpeg.org>E<gt>.

Maintainers for the specific components are listed in the file
F<MAINTAINERS> in the source code tree.