yading@10: =head1 NAME
yading@10: 
yading@10: ffmpeg-resampler - FFmpeg Resampler
yading@10: 
yading@10: =head1 DESCRIPTION
yading@10: 
yading@10: 
yading@10: The FFmpeg resampler provides an high-level interface to the
yading@10: libswresample library audio resampling utilities. In particular it
yading@10: allows to perform audio resampling, audio channel layout rematrixing,
yading@10: and convert audio format and packing layout.
yading@10: 
yading@10: 
yading@10: 
yading@10: =head1 RESAMPLER OPTIONS
yading@10: 
yading@10: 
yading@10: The audio resampler supports the following named options.
yading@10: 
yading@10: Options may be set by specifying -I<option> I<value> in the
yading@10: FFmpeg tools, I<option>=I<value> for the aresample filter,
yading@10: by setting the value explicitly in the
yading@10: C<SwrContext> options or using the F<libavutil/opt.h> API for
yading@10: programmatic use.
yading@10: 
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: 
yading@10: =item B<ich, in_channel_count>
yading@10: 
yading@10: Set the number of input channels. Default value is 0. Setting this
yading@10: value is not mandatory if the corresponding channel layout
yading@10: B<in_channel_layout> is set.
yading@10: 
yading@10: 
yading@10: =item B<och, out_channel_count>
yading@10: 
yading@10: Set the number of output channels. Default value is 0. Setting this
yading@10: value is not mandatory if the corresponding channel layout
yading@10: B<out_channel_layout> is set.
yading@10: 
yading@10: 
yading@10: =item B<uch, used_channel_count>
yading@10: 
yading@10: Set the number of used input channels. Default value is 0. This option is
yading@10: only used for special remapping.
yading@10: 
yading@10: 
yading@10: =item B<isr, in_sample_rate>
yading@10: 
yading@10: Set the input sample rate. Default value is 0.
yading@10: 
yading@10: 
yading@10: =item B<osr, out_sample_rate>
yading@10: 
yading@10: Set the output sample rate. Default value is 0.
yading@10: 
yading@10: 
yading@10: =item B<isf, in_sample_fmt>
yading@10: 
yading@10: Specify the input sample format. It is set by default to C<none>.
yading@10: 
yading@10: 
yading@10: =item B<osf, out_sample_fmt>
yading@10: 
yading@10: Specify the output sample format. It is set by default to C<none>.
yading@10: 
yading@10: 
yading@10: =item B<tsf, internal_sample_fmt>
yading@10: 
yading@10: Set the internal sample format. Default value is C<none>.
yading@10: This will automatically be chosen when it is not explicitly set.
yading@10: 
yading@10: 
yading@10: =item B<icl, in_channel_layout>
yading@10: 
yading@10: Set the input channel layout.
yading@10: 
yading@10: 
yading@10: =item B<ocl, out_channel_layout>
yading@10: 
yading@10: Set the output channel layout.
yading@10: 
yading@10: 
yading@10: =item B<clev, center_mix_level>
yading@10: 
yading@10: Set the center mix level. It is a value expressed in deciBel, and must be
yading@10: in the interval [-32,32].
yading@10: 
yading@10: 
yading@10: =item B<slev, surround_mix_level>
yading@10: 
yading@10: Set the surround mix level. It is a value expressed in deciBel, and must
yading@10: be in the interval [-32,32].
yading@10: 
yading@10: 
yading@10: =item B<lfe_mix_level>
yading@10: 
yading@10: Set LFE mix into non LFE level. It is used when there is a LFE input but no
yading@10: LFE output. It is a value expressed in deciBel, and must
yading@10: be in the interval [-32,32].
yading@10: 
yading@10: 
yading@10: =item B<rmvol, rematrix_volume>
yading@10: 
yading@10: Set rematrix volume. Default value is 1.0.
yading@10: 
yading@10: 
yading@10: =item B<flags, swr_flags>
yading@10: 
yading@10: Set flags used by the converter. Default value is 0.
yading@10: 
yading@10: It supports the following individual flags:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<res>
yading@10: 
yading@10: force resampling, this flag forces resampling to be used even when the
yading@10: input and output sample rates match.
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: =item B<dither_scale>
yading@10: 
yading@10: Set the dither scale. Default value is 1.
yading@10: 
yading@10: 
yading@10: =item B<dither_method>
yading@10: 
yading@10: Set dither method. Default value is 0.
yading@10: 
yading@10: Supported values:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<rectangular>
yading@10: 
yading@10: select rectangular dither
yading@10: 
yading@10: =item B<triangular>
yading@10: 
yading@10: select triangular dither
yading@10: 
yading@10: =item B<triangular_hp>
yading@10: 
yading@10: select triangular dither with high pass
yading@10: 
yading@10: =item B<lipshitz>
yading@10: 
yading@10: select lipshitz noise shaping dither
yading@10: 
yading@10: =item B<shibata>
yading@10: 
yading@10: select shibata noise shaping dither
yading@10: 
yading@10: =item B<low_shibata>
yading@10: 
yading@10: select low shibata noise shaping dither
yading@10: 
yading@10: =item B<high_shibata>
yading@10: 
yading@10: select high shibata noise shaping dither
yading@10: 
yading@10: =item B<f_weighted>
yading@10: 
yading@10: select f-weighted noise shaping dither
yading@10: 
yading@10: =item B<modified_e_weighted>
yading@10: 
yading@10: select modified-e-weighted noise shaping dither
yading@10: 
yading@10: =item B<improved_e_weighted>
yading@10: 
yading@10: select improved-e-weighted noise shaping dither
yading@10: 
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: =item B<resampler>
yading@10: 
yading@10: Set resampling engine. Default value is swr.
yading@10: 
yading@10: Supported values:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<swr>
yading@10: 
yading@10: select the native SW Resampler; filter options precision and cheby are not
yading@10: applicable in this case.
yading@10: 
yading@10: =item B<soxr>
yading@10: 
yading@10: select the SoX Resampler (where available); compensation, and filter options
yading@10: filter_size, phase_shift, filter_type & kaiser_beta, are not applicable in this
yading@10: case.
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: =item B<filter_size>
yading@10: 
yading@10: For swr only, set resampling filter size, default value is 32.
yading@10: 
yading@10: 
yading@10: =item B<phase_shift>
yading@10: 
yading@10: For swr only, set resampling phase shift, default value is 10, and must be in
yading@10: the interval [0,30].
yading@10: 
yading@10: 
yading@10: =item B<linear_interp>
yading@10: 
yading@10: Use Linear Interpolation if set to 1, default value is 0.
yading@10: 
yading@10: 
yading@10: =item B<cutoff>
yading@10: 
yading@10: Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must be a float
yading@10: value between 0 and 1.  Default value is 0.97 with swr, and 0.91 with soxr
yading@10: (which, with a sample-rate of 44100, preserves the entire audio band to 20kHz).
yading@10: 
yading@10: 
yading@10: =item B<precision>
yading@10: 
yading@10: For soxr only, the precision in bits to which the resampled signal will be
yading@10: calculated.  The default value of 20 (which, with suitable dithering, is
yading@10: appropriate for a destination bit-depth of 16) gives SoX's 'High Quality'; a
yading@10: value of 28 gives SoX's 'Very High Quality'.
yading@10: 
yading@10: 
yading@10: =item B<cheby>
yading@10: 
yading@10: For soxr only, selects passband rolloff none (Chebyshev) & higher-precision
yading@10: approximation for 'irrational' ratios. Default value is 0.
yading@10: 
yading@10: 
yading@10: =item B<async>
yading@10: 
yading@10: For swr only, simple 1 parameter audio sync to timestamps using stretching,
yading@10: squeezing, filling and trimming. Setting this to 1 will enable filling and
yading@10: trimming, larger values represent the maximum amount in samples that the data
yading@10: may be stretched or squeezed for each second.
yading@10: Default value is 0, thus no compensation is applied to make the samples match
yading@10: the audio timestamps.
yading@10: 
yading@10: 
yading@10: =item B<first_pts>
yading@10: 
yading@10: For swr only, assume the first pts should be this value. The time unit is 1 / sample rate.
yading@10: This allows for padding/trimming at the start of stream. By default, no
yading@10: assumption is made about the first frame's expected pts, so no padding or
yading@10: trimming is done. For example, this could be set to 0 to pad the beginning with
yading@10: silence if an audio stream starts after the video stream or to trim any samples
yading@10: with a negative pts due to encoder delay.
yading@10: 
yading@10: 
yading@10: =item B<min_comp>
yading@10: 
yading@10: For swr only, set the minimum difference between timestamps and audio data (in
yading@10: seconds) to trigger stretching/squeezing/filling or trimming of the
yading@10: data to make it match the timestamps. The default is that
yading@10: stretching/squeezing/filling and trimming is disabled
yading@10: (B<min_comp> = C<FLT_MAX>).
yading@10: 
yading@10: 
yading@10: =item B<min_hard_comp>
yading@10: 
yading@10: For swr only, set the minimum difference between timestamps and audio data (in
yading@10: seconds) to trigger adding/dropping samples to make it match the
yading@10: timestamps.  This option effectively is a threshold to select between
yading@10: hard (trim/fill) and soft (squeeze/stretch) compensation. Note that
yading@10: all compensation is by default disabled through B<min_comp>.
yading@10: The default is 0.1.
yading@10: 
yading@10: 
yading@10: =item B<comp_duration>
yading@10: 
yading@10: For swr only, set duration (in seconds) over which data is stretched/squeezed
yading@10: to make it match the timestamps. Must be a non-negative double float value,
yading@10: default value is 1.0.
yading@10: 
yading@10: 
yading@10: =item B<max_soft_comp>
yading@10: 
yading@10: For swr only, set maximum factor by which data is stretched/squeezed to make it
yading@10: match the timestamps. Must be a non-negative double float value, default value
yading@10: is 0.
yading@10: 
yading@10: 
yading@10: =item B<matrix_encoding>
yading@10: 
yading@10: Select matrixed stereo encoding.
yading@10: 
yading@10: It accepts the following values:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<none>
yading@10: 
yading@10: select none
yading@10: 
yading@10: =item B<dolby>
yading@10: 
yading@10: select Dolby
yading@10: 
yading@10: =item B<dplii>
yading@10: 
yading@10: select Dolby Pro Logic II
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: Default value is C<none>.
yading@10: 
yading@10: 
yading@10: =item B<filter_type>
yading@10: 
yading@10: For swr only, select resampling filter type. This only affects resampling
yading@10: operations.
yading@10: 
yading@10: It accepts the following values:
yading@10: 
yading@10: =over 4
yading@10: 
yading@10: 
yading@10: =item B<cubic>
yading@10: 
yading@10: select cubic
yading@10: 
yading@10: =item B<blackman_nuttall>
yading@10: 
yading@10: select Blackman Nuttall Windowed Sinc
yading@10: 
yading@10: =item B<kaiser>
yading@10: 
yading@10: select Kaiser Windowed Sinc
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: =item B<kaiser_beta>
yading@10: 
yading@10: For swr only, set Kaiser Window Beta value. Must be an integer in the
yading@10: interval [2,16], default value is 9.
yading@10: 
yading@10: 
yading@10: =back
yading@10: 
yading@10: 
yading@10: 
yading@10: 
yading@10: =head1 SEE ALSO
yading@10: 
yading@10: 
yading@10: 
yading@10: ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libswresample(3)
yading@10: 
yading@10: 
yading@10: =head1 AUTHORS
yading@10: 
yading@10: 
yading@10: The FFmpeg developers.
yading@10: 
yading@10: For details about the authorship, see the Git history of the project
yading@10: (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
yading@10: B<git log> in the FFmpeg source directory, or browsing the
yading@10: online repository at E<lt>B<http://source.ffmpeg.org>E<gt>.
yading@10: 
yading@10: Maintainers for the specific components are listed in the file
yading@10: F<MAINTAINERS> in the source code tree.
yading@10: 
yading@10: 
yading@10: