yading@10: \input texinfo @c -*- texinfo -*-
yading@10: 
yading@10: @settitle FFmpeg FAQ
yading@10: @titlepage
yading@10: @center @titlefont{FFmpeg FAQ}
yading@10: @end titlepage
yading@10: 
yading@10: @top
yading@10: 
yading@10: @contents
yading@10: 
yading@10: @chapter General Questions
yading@10: 
yading@10: @section Why doesn't FFmpeg support feature [xyz]?
yading@10: 
yading@10: Because no one has taken on that task yet. FFmpeg development is
yading@10: driven by the tasks that are important to the individual developers.
yading@10: If there is a feature that is important to you, the best way to get
yading@10: it implemented is to undertake the task yourself or sponsor a developer.
yading@10: 
yading@10: @section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?
yading@10: 
yading@10: No. Windows DLLs are not portable, bloated and often slow.
yading@10: Moreover FFmpeg strives to support all codecs natively.
yading@10: A DLL loader is not conducive to that goal.
yading@10: 
yading@10: @section I cannot read this file although this format seems to be supported by ffmpeg.
yading@10: 
yading@10: Even if ffmpeg can read the container format, it may not support all its
yading@10: codecs. Please consult the supported codec list in the ffmpeg
yading@10: documentation.
yading@10: 
yading@10: @section Which codecs are supported by Windows?
yading@10: 
yading@10: Windows does not support standard formats like MPEG very well, unless you
yading@10: install some additional codecs.
yading@10: 
yading@10: The following list of video codecs should work on most Windows systems:
yading@10: @table @option
yading@10: @item msmpeg4v2
yading@10: .avi/.asf
yading@10: @item msmpeg4
yading@10: .asf only
yading@10: @item wmv1
yading@10: .asf only
yading@10: @item wmv2
yading@10: .asf only
yading@10: @item mpeg4
yading@10: Only if you have some MPEG-4 codec like ffdshow or Xvid installed.
yading@10: @item mpeg1video
yading@10: .mpg only
yading@10: @end table
yading@10: Note, ASF files often have .wmv or .wma extensions in Windows. It should also
yading@10: be mentioned that Microsoft claims a patent on the ASF format, and may sue
yading@10: or threaten users who create ASF files with non-Microsoft software. It is
yading@10: strongly advised to avoid ASF where possible.
yading@10: 
yading@10: The following list of audio codecs should work on most Windows systems:
yading@10: @table @option
yading@10: @item adpcm_ima_wav
yading@10: @item adpcm_ms
yading@10: @item pcm_s16le
yading@10: always
yading@10: @item libmp3lame
yading@10: If some MP3 codec like LAME is installed.
yading@10: @end table
yading@10: 
yading@10: 
yading@10: @chapter Compilation
yading@10: 
yading@10: @section @code{error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'}
yading@10: 
yading@10: This is a bug in gcc. Do not report it to us. Instead, please report it to
yading@10: the gcc developers. Note that we will not add workarounds for gcc bugs.
yading@10: 
yading@10: Also note that (some of) the gcc developers believe this is not a bug or
yading@10: not a bug they should fix:
yading@10: @url{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203}.
yading@10: Then again, some of them do not know the difference between an undecidable
yading@10: problem and an NP-hard problem...
yading@10: 
yading@10: @section I have installed this library with my distro's package manager. Why does @command{configure} not see it?
yading@10: 
yading@10: Distributions usually split libraries in several packages. The main package
yading@10: contains the files necessary to run programs using the library. The
yading@10: development package contains the files necessary to build programs using the
yading@10: library. Sometimes, docs and/or data are in a separate package too.
yading@10: 
yading@10: To build FFmpeg, you need to install the development package. It is usually
yading@10: called @file{libfoo-dev} or @file{libfoo-devel}. You can remove it after the
yading@10: build is finished, but be sure to keep the main package.
yading@10: 
yading@10: @chapter Usage
yading@10: 
yading@10: @section ffmpeg does not work; what is wrong?
yading@10: 
yading@10: Try a @code{make distclean} in the ffmpeg source directory before the build.
yading@10: If this does not help see
yading@10: (@url{http://ffmpeg.org/bugreports.html}).
yading@10: 
yading@10: @section How do I encode single pictures into movies?
yading@10: 
yading@10: First, rename your pictures to follow a numerical sequence.
yading@10: For example, img1.jpg, img2.jpg, img3.jpg,...
yading@10: Then you may run:
yading@10: 
yading@10: @example
yading@10:   ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
yading@10: @end example
yading@10: 
yading@10: Notice that @samp{%d} is replaced by the image number.
yading@10: 
yading@10: @file{img%03d.jpg} means the sequence @file{img001.jpg}, @file{img002.jpg}, etc.
yading@10: 
yading@10: Use the @option{-start_number} option to declare a starting number for
yading@10: the sequence. This is useful if your sequence does not start with
yading@10: @file{img001.jpg} but is still in a numerical order. The following
yading@10: example will start with @file{img100.jpg}:
yading@10: 
yading@10: @example
yading@10:   ffmpeg -f image2 -start_number 100 -i img%d.jpg /tmp/a.mpg
yading@10: @end example
yading@10: 
yading@10: If you have large number of pictures to rename, you can use the
yading@10: following command to ease the burden. The command, using the bourne
yading@10: shell syntax, symbolically links all files in the current directory
yading@10: that match @code{*jpg} to the @file{/tmp} directory in the sequence of
yading@10: @file{img001.jpg}, @file{img002.jpg} and so on.
yading@10: 
yading@10: @example
yading@10:   x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s "$i" /tmp/img"$counter".jpg; x=$(($x+1)); done
yading@10: @end example
yading@10: 
yading@10: If you want to sequence them by oldest modified first, substitute
yading@10: @code{$(ls -r -t *jpg)} in place of @code{*jpg}.
yading@10: 
yading@10: Then run:
yading@10: 
yading@10: @example
yading@10:   ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg
yading@10: @end example
yading@10: 
yading@10: The same logic is used for any image format that ffmpeg reads.
yading@10: 
yading@10: You can also use @command{cat} to pipe images to ffmpeg:
yading@10: 
yading@10: @example
yading@10:   cat *.jpg | ffmpeg -f image2pipe -c:v mjpeg -i - output.mpg
yading@10: @end example
yading@10: 
yading@10: @section How do I encode movie to single pictures?
yading@10: 
yading@10: Use:
yading@10: 
yading@10: @example
yading@10:   ffmpeg -i movie.mpg movie%d.jpg
yading@10: @end example
yading@10: 
yading@10: The @file{movie.mpg} used as input will be converted to
yading@10: @file{movie1.jpg}, @file{movie2.jpg}, etc...
yading@10: 
yading@10: Instead of relying on file format self-recognition, you may also use
yading@10: @table @option
yading@10: @item -c:v ppm
yading@10: @item -c:v png
yading@10: @item -c:v mjpeg
yading@10: @end table
yading@10: to force the encoding.
yading@10: 
yading@10: Applying that to the previous example:
yading@10: @example
yading@10:   ffmpeg -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg
yading@10: @end example
yading@10: 
yading@10: Beware that there is no "jpeg" codec. Use "mjpeg" instead.
yading@10: 
yading@10: @section Why do I see a slight quality degradation with multithreaded MPEG* encoding?
yading@10: 
yading@10: For multithreaded MPEG* encoding, the encoded slices must be independent,
yading@10: otherwise thread n would practically have to wait for n-1 to finish, so it's
yading@10: quite logical that there is a small reduction of quality. This is not a bug.
yading@10: 
yading@10: @section How can I read from the standard input or write to the standard output?
yading@10: 
yading@10: Use @file{-} as file name.
yading@10: 
yading@10: @section -f jpeg doesn't work.
yading@10: 
yading@10: Try '-f image2 test%d.jpg'.
yading@10: 
yading@10: @section Why can I not change the frame rate?
yading@10: 
yading@10: Some codecs, like MPEG-1/2, only allow a small number of fixed frame rates.
yading@10: Choose a different codec with the -c:v command line option.
yading@10: 
yading@10: @section How do I encode Xvid or DivX video with ffmpeg?
yading@10: 
yading@10: Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4
yading@10: standard (note that there are many other coding formats that use this
yading@10: same standard). Thus, use '-c:v mpeg4' to encode in these formats. The
yading@10: default fourcc stored in an MPEG-4-coded file will be 'FMP4'. If you want
yading@10: a different fourcc, use the '-vtag' option. E.g., '-vtag xvid' will
yading@10: force the fourcc 'xvid' to be stored as the video fourcc rather than the
yading@10: default.
yading@10: 
yading@10: @section Which are good parameters for encoding high quality MPEG-4?
yading@10: 
yading@10: '-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2',
yading@10: things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'.
yading@10: 
yading@10: @section Which are good parameters for encoding high quality MPEG-1/MPEG-2?
yading@10: 
yading@10: '-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2'
yading@10: but beware the '-g 100' might cause problems with some decoders.
yading@10: Things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd.
yading@10: 
yading@10: @section Interlaced video looks very bad when encoded with ffmpeg, what is wrong?
yading@10: 
yading@10: You should use '-flags +ilme+ildct' and maybe '-flags +alt' for interlaced
yading@10: material, and try '-top 0/1' if the result looks really messed-up.
yading@10: 
yading@10: @section How can I read DirectShow files?
yading@10: 
yading@10: If you have built FFmpeg with @code{./configure --enable-avisynth}
yading@10: (only possible on MinGW/Cygwin platforms),
yading@10: then you may use any file that DirectShow can read as input.
yading@10: 
yading@10: Just create an "input.avs" text file with this single line ...
yading@10: @example
yading@10:   DirectShowSource("C:\path to your file\yourfile.asf")
yading@10: @end example
yading@10: ... and then feed that text file to ffmpeg:
yading@10: @example
yading@10:   ffmpeg -i input.avs
yading@10: @end example
yading@10: 
yading@10: For ANY other help on Avisynth, please visit the
yading@10: @uref{http://www.avisynth.org/, Avisynth homepage}.
yading@10: 
yading@10: @section How can I join video files?
yading@10: 
yading@10: To "join" video files is quite ambiguous. The following list explains the
yading@10: different kinds of "joining" and points out how those are addressed in
yading@10: FFmpeg. To join video files may mean:
yading@10: 
yading@10: @itemize
yading@10: 
yading@10: @item
yading@10: To put them one after the other: this is called to @emph{concatenate} them
yading@10: (in short: concat) and is addressed
yading@10: @ref{How can I concatenate video files, in this very faq}.
yading@10: 
yading@10: @item
yading@10: To put them together in the same file, to let the user choose between the
yading@10: different versions (example: different audio languages): this is called to
yading@10: @emph{multiplex} them together (in short: mux), and is done by simply
yading@10: invoking ffmpeg with several @option{-i} options.
yading@10: 
yading@10: @item
yading@10: For audio, to put all channels together in a single stream (example: two
yading@10: mono streams into one stereo stream): this is sometimes called to
yading@10: @emph{merge} them, and can be done using the
yading@10: @url{http://ffmpeg.org/ffmpeg-filters.html#amerge, @code{amerge}} filter.
yading@10: 
yading@10: @item
yading@10: For audio, to play one on top of the other: this is called to @emph{mix}
yading@10: them, and can be done by first merging them into a single stream and then
yading@10: using the @url{http://ffmpeg.org/ffmpeg-filters.html#pan, @code{pan}} filter to mix
yading@10: the channels at will.
yading@10: 
yading@10: @item
yading@10: For video, to display both together, side by side or one on top of a part of
yading@10: the other; it can be done using the
yading@10: @url{http://ffmpeg.org/ffmpeg-filters.html#overlay, @code{overlay}} video filter.
yading@10: 
yading@10: @end itemize
yading@10: 
yading@10: @anchor{How can I concatenate video files}
yading@10: @section How can I concatenate video files?
yading@10: 
yading@10: There are several solutions, depending on the exact circumstances.
yading@10: 
yading@10: @subsection Concatenating using the concat @emph{filter}
yading@10: 
yading@10: FFmpeg has a @url{http://ffmpeg.org/ffmpeg-filters.html#concat,
yading@10: @code{concat}} filter designed specifically for that, with examples in the
yading@10: documentation. This operation is recommended if you need to re-encode.
yading@10: 
yading@10: @subsection Concatenating using the concat @emph{demuxer}
yading@10: 
yading@10: FFmpeg has a @url{http://www.ffmpeg.org/ffmpeg-formats.html#concat,
yading@10: @code{concat}} demuxer which you can use when you want to avoid a re-encode and
yading@10: your format doesn't support file level concatenation.
yading@10: 
yading@10: @subsection Concatenating using the concat @emph{protocol} (file level)
yading@10: 
yading@10: FFmpeg has a @url{http://ffmpeg.org/ffmpeg-protocols.html#concat,
yading@10: @code{concat}} protocol designed specifically for that, with examples in the
yading@10: documentation.
yading@10: 
yading@10: A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow to concatenate
yading@10: video by merely concatenating the files containing them.
yading@10: 
yading@10: Hence you may concatenate your multimedia files by first transcoding them to
yading@10: these privileged formats, then using the humble @code{cat} command (or the
yading@10: equally humble @code{copy} under Windows), and finally transcoding back to your
yading@10: format of choice.
yading@10: 
yading@10: @example
yading@10: ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
yading@10: ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
yading@10: cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg
yading@10: ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
yading@10: @end example
yading@10: 
yading@10: Additionally, you can use the @code{concat} protocol instead of @code{cat} or
yading@10: @code{copy} which will avoid creation of a potentially huge intermediate file.
yading@10: 
yading@10: @example
yading@10: ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
yading@10: ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
yading@10: ffmpeg -i concat:"intermediate1.mpg|intermediate2.mpg" -c copy intermediate_all.mpg
yading@10: ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
yading@10: @end example
yading@10: 
yading@10: Note that you may need to escape the character "|" which is special for many
yading@10: shells.
yading@10: 
yading@10: Another option is usage of named pipes, should your platform support it:
yading@10: 
yading@10: @example
yading@10: mkfifo intermediate1.mpg
yading@10: mkfifo intermediate2.mpg
yading@10: ffmpeg -i input1.avi -qscale:v 1 -y intermediate1.mpg < /dev/null &
yading@10: ffmpeg -i input2.avi -qscale:v 1 -y intermediate2.mpg < /dev/null &
yading@10: cat intermediate1.mpg intermediate2.mpg |\
yading@10: ffmpeg -f mpeg -i - -c:v mpeg4 -acodec libmp3lame output.avi
yading@10: @end example
yading@10: 
yading@10: @subsection Concatenating using raw audio and video
yading@10: 
yading@10: Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also
yading@10: allow concatenation, and the transcoding step is almost lossless.
yading@10: When using multiple yuv4mpegpipe(s), the first line needs to be discarded
yading@10: from all but the first stream. This can be accomplished by piping through
yading@10: @code{tail} as seen below. Note that when piping through @code{tail} you
yading@10: must use command grouping, @code{@{  ;@}}, to background properly.
yading@10: 
yading@10: For example, let's say we want to concatenate two FLV files into an
yading@10: output.flv file:
yading@10: 
yading@10: @example
yading@10: mkfifo temp1.a
yading@10: mkfifo temp1.v
yading@10: mkfifo temp2.a
yading@10: mkfifo temp2.v
yading@10: mkfifo all.a
yading@10: mkfifo all.v
yading@10: ffmpeg -i input1.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp1.a < /dev/null &
yading@10: ffmpeg -i input2.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp2.a < /dev/null &
yading@10: ffmpeg -i input1.flv -an -f yuv4mpegpipe - > temp1.v < /dev/null &
yading@10: @{ ffmpeg -i input2.flv -an -f yuv4mpegpipe - < /dev/null | tail -n +2 > temp2.v ; @} &
yading@10: cat temp1.a temp2.a > all.a &
yading@10: cat temp1.v temp2.v > all.v &
yading@10: ffmpeg -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \
yading@10:        -f yuv4mpegpipe -i all.v \
yading@10:        -y output.flv
yading@10: rm temp[12].[av] all.[av]
yading@10: @end example
yading@10: 
yading@10: @section -profile option fails when encoding H.264 video with AAC audio
yading@10: 
yading@10: @command{ffmpeg} prints an error like
yading@10: 
yading@10: @example
yading@10: Undefined constant or missing '(' in 'baseline'
yading@10: Unable to parse option value "baseline"
yading@10: Error setting option profile to value baseline.
yading@10: @end example
yading@10: 
yading@10: Short answer: write @option{-profile:v} instead of @option{-profile}.
yading@10: 
yading@10: Long answer: this happens because the @option{-profile} option can apply to both
yading@10: video and audio.  Specifically the AAC encoder also defines some profiles, none
yading@10: of which are named @var{baseline}.
yading@10: 
yading@10: The solution is to apply the @option{-profile} option to the video stream only
yading@10: by using @url{http://ffmpeg.org/ffmpeg.html#Stream-specifiers-1, Stream specifiers}.
yading@10: Appending @code{:v} to it will do exactly that.
yading@10: 
yading@10: @section Using @option{-f lavfi}, audio becomes mono for no apparent reason.
yading@10: 
yading@10: Use @option{-dumpgraph -} to find out exactly where the channel layout is
yading@10: lost.
yading@10: 
yading@10: Most likely, it is through @code{auto-inserted aresample}. Try to understand
yading@10: why the converting filter was needed at that place.
yading@10: 
yading@10: Just before the output is a likely place, as @option{-f lavfi} currently
yading@10: only support packed S16.
yading@10: 
yading@10: Then insert the correct @code{aformat} explicitly in the filtergraph,
yading@10: specifying the exact format.
yading@10: 
yading@10: @example
yading@10: aformat=sample_fmts=s16:channel_layouts=stereo
yading@10: @end example
yading@10: 
yading@10: @section Why does FFmpeg not see the subtitles in my VOB file?
yading@10: 
yading@10: VOB and a few other formats do not have a global header that describes
yading@10: everything present in the file. Instead, applications are supposed to scan
yading@10: the file to see what it contains. Since VOB files are frequently large, only
yading@10: the beginning is scanned. If the subtitles happen only later in the file,
yading@10: they will not be initally detected.
yading@10: 
yading@10: Some applications, including the @code{ffmpeg} command-line tool, can only
yading@10: work with streams that were detected during the initial scan; streams that
yading@10: are detected later are ignored.
yading@10: 
yading@10: The size of the initial scan is controlled by two options: @code{probesize}
yading@10: (default ~5 Mo) and @code{analyzeduration} (default 5,000,000 µs = 5 s). For
yading@10: the subtitle stream to be detected, both values must be large enough.
yading@10: 
yading@10: @section Why was the @command{ffmpeg} @option{-sameq} option removed? What to use instead?
yading@10: 
yading@10: The @option{-sameq} option meant "same quantizer", and made sense only in a
yading@10: very limited set of cases. Unfortunately, a lot of people mistook it for
yading@10: "same quality" and used it in places where it did not make sense: it had
yading@10: roughly the expected visible effect, but achieved it in a very inefficient
yading@10: way.
yading@10: 
yading@10: Each encoder has its own set of options to set the quality-vs-size balance,
yading@10: use the options for the encoder you are using to set the quality level to a
yading@10: point acceptable for your tastes. The most common options to do that are
yading@10: @option{-qscale} and @option{-qmax}, but you should peruse the documentation
yading@10: of the encoder you chose.
yading@10: 
yading@10: @chapter Development
yading@10: 
yading@10: @section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?
yading@10: 
yading@10: Yes. Check the @file{doc/examples} directory in the source
yading@10: repository, also available online at:
yading@10: @url{https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples}.
yading@10: 
yading@10: Examples are also installed by default, usually in
yading@10: @code{$PREFIX/share/ffmpeg/examples}.
yading@10: 
yading@10: Also you may read the Developers Guide of the FFmpeg documentation. Alternatively,
yading@10: examine the source code for one of the many open source projects that
yading@10: already incorporate FFmpeg at (@url{projects.html}).
yading@10: 
yading@10: @section Can you support my C compiler XXX?
yading@10: 
yading@10: It depends. If your compiler is C99-compliant, then patches to support
yading@10: it are likely to be welcome if they do not pollute the source code
yading@10: with @code{#ifdef}s related to the compiler.
yading@10: 
yading@10: @section Is Microsoft Visual C++ supported?
yading@10: 
yading@10: Yes. Please see the @uref{platform.html, Microsoft Visual C++}
yading@10: section in the FFmpeg documentation.
yading@10: 
yading@10: @section Can you add automake, libtool or autoconf support?
yading@10: 
yading@10: No. These tools are too bloated and they complicate the build.
yading@10: 
yading@10: @section Why not rewrite FFmpeg in object-oriented C++?
yading@10: 
yading@10: FFmpeg is already organized in a highly modular manner and does not need to
yading@10: be rewritten in a formal object language. Further, many of the developers
yading@10: favor straight C; it works for them. For more arguments on this matter,
yading@10: read @uref{http://www.tux.org/lkml/#s15, "Programming Religion"}.
yading@10: 
yading@10: @section Why are the ffmpeg programs devoid of debugging symbols?
yading@10: 
yading@10: The build process creates ffmpeg_g, ffplay_g, etc. which contain full debug
yading@10: information. Those binaries are stripped to create ffmpeg, ffplay, etc. If
yading@10: you need the debug information, use the *_g versions.
yading@10: 
yading@10: @section I do not like the LGPL, can I contribute code under the GPL instead?
yading@10: 
yading@10: Yes, as long as the code is optional and can easily and cleanly be placed
yading@10: under #if CONFIG_GPL without breaking anything. So, for example, a new codec
yading@10: or filter would be OK under GPL while a bug fix to LGPL code would not.
yading@10: 
yading@10: @section I'm using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.
yading@10: 
yading@10: FFmpeg builds static libraries by default. In static libraries, dependencies
yading@10: are not handled. That has two consequences. First, you must specify the
yading@10: libraries in dependency order: @code{-lavdevice} must come before
yading@10: @code{-lavformat}, @code{-lavutil} must come after everything else, etc.
yading@10: Second, external libraries that are used in FFmpeg have to be specified too.
yading@10: 
yading@10: An easy way to get the full list of required libraries in dependency order
yading@10: is to use @code{pkg-config}.
yading@10: 
yading@10: @example
yading@10:   c99 -o program program.c $(pkg-config --cflags --libs libavformat libavcodec)
yading@10: @end example
yading@10: 
yading@10: See @file{doc/example/Makefile} and @file{doc/example/pc-uninstalled} for
yading@10: more details.
yading@10: 
yading@10: @section I'm using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.
yading@10: 
yading@10: FFmpeg is a pure C project, so to use the libraries within your C++ application
yading@10: you need to explicitly state that you are using a C library. You can do this by
yading@10: encompassing your FFmpeg includes using @code{extern "C"}.
yading@10: 
yading@10: See @url{http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3}
yading@10: 
yading@10: @section I'm using libavutil from within my C++ application but the compiler complains about 'UINT64_C' was not declared in this scope
yading@10: 
yading@10: FFmpeg is a pure C project using C99 math features, in order to enable C++
yading@10: to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS
yading@10: 
yading@10: @section I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?
yading@10: 
yading@10: You have to create a custom AVIOContext using @code{avio_alloc_context},
yading@10: see @file{libavformat/aviobuf.c} in FFmpeg and @file{libmpdemux/demux_lavf.c} in MPlayer or MPlayer2 sources.
yading@10: 
yading@10: @section Where can I find libav* headers for Pascal/Delphi?
yading@10: 
yading@10: see @url{http://www.iversenit.dk/dev/ffmpeg-headers/}
yading@10: 
yading@10: @section Where is the documentation about ffv1, msmpeg4, asv1, 4xm?
yading@10: 
yading@10: see @url{http://www.ffmpeg.org/~michael/}
yading@10: 
yading@10: @section How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?
yading@10: 
yading@10: Even if peculiar since it is network oriented, RTP is a container like any
yading@10: other. You have to @emph{demux} RTP before feeding the payload to libavcodec.
yading@10: In this specific case please look at RFC 4629 to see how it should be done.
yading@10: 
yading@10: @section AVStream.r_frame_rate is wrong, it is much larger than the frame rate.
yading@10: 
yading@10: r_frame_rate is NOT the average frame rate, it is the smallest frame rate
yading@10: that can accurately represent all timestamps. So no, it is not
yading@10: wrong if it is larger than the average!
yading@10: For example, if you have mixed 25 and 30 fps content, then r_frame_rate
yading@10: will be 150.
yading@10: 
yading@10: @section Why is @code{make fate} not running all tests?
yading@10: 
yading@10: Make sure you have the fate-suite samples and the @code{SAMPLES} Make variable
yading@10: or @code{FATE_SAMPLES} environment variable or the @code{--samples}
yading@10: @command{configure} option is set to the right path.
yading@10: 
yading@10: @section Why is @code{make fate} not finding the samples?
yading@10: 
yading@10: Do you happen to have a @code{~} character in the samples path to indicate a
yading@10: home directory? The value is used in ways where the shell cannot expand it,
yading@10: causing FATE to not find files. Just replace @code{~} by the full path.
yading@10: 
yading@10: @bye