\input texinfo @c -*- texinfo -*-
-@settitle FFmpeg FAQ
+@settitle Libav FAQ
@titlepage
-@sp 7
-@center @titlefont{FFmpeg FAQ}
-@sp 3
+@center @titlefont{Libav FAQ}
@end titlepage
+@top
-@chapter General Questions
-
-@section When will the next FFmpeg version be released? / Why are FFmpeg releases so few and far between?
-
-Like most open source projects FFmpeg suffers from a certain lack of
-manpower. For this reason the developers have to prioritize the work
-they do and putting out releases is not at the top of the list, fixing
-bugs and reviewing patches takes precedence. Please don't complain or
-request more timely and/or frequent releases unless you are willing to
-help out creating them.
+@contents
-@section I have a problem with an old version of FFmpeg; where should I report it?
-Nowhere. Upgrade to the latest release or if there is no recent release upgrade
-to Subversion HEAD. You could also try to report it. Maybe you will get lucky and
-become the first person in history to get an answer different from "upgrade
-to Subversion HEAD".
+@chapter General Questions
-@section Why doesn't FFmpeg support feature [xyz]?
+@section Why doesn't Libav support feature [xyz]?
-Because no one has taken on that task yet. FFmpeg development is
+Because no one has taken on that task yet. Libav development is
driven by the tasks that are important to the individual developers.
If there is a feature that is important to you, the best way to get
it implemented is to undertake the task yourself or sponsor a developer.
-@section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?
+@section Libav does not support codec XXX. Can you include a Windows DLL loader to support it?
No. Windows DLLs are not portable, bloated and often slow.
-Moreover FFmpeg strives to support all codecs natively.
+Moreover Libav strives to support all codecs natively.
A DLL loader is not conducive to that goal.
-@section My bug report/mail to ffmpeg-devel/user has not received any replies.
-
-Likely reasons
-@itemize
-@item We are busy and haven't had time yet to read your report or
-investigate the issue.
-@item You didn't follow bugreports.html.
-@item You didn't use Subversion HEAD.
-@item You reported a segmentation fault without gdb output.
-@item You describe a problem but not how to reproduce it.
-@item It's unclear if you use ffmpeg as command line tool or use
-libav* from another application.
-@item You speak about a video having problems on playback but
-not what you use to play it.
-@item We have no faint clue what you are talking about besides
-that it is related to FFmpeg.
-@end itemize
-
-@section Is there a forum for FFmpeg? I do not like mailing lists.
-
-You may view our mailing lists with a more forum-alike look here:
-@url{http://dir.gmane.org/gmane.comp.video.ffmpeg.user},
-but, if you post, please remember that our mailing list rules still apply there.
-
-@section I cannot read this file although this format seems to be supported by ffmpeg.
-
-Even if ffmpeg can read the container format, it may not support all its
-codecs. Please consult the supported codec list in the ffmpeg
+@section I cannot read this file although this format seems to be supported by avconv.
+
+Even if avconv can read the container format, it may not support all its
+codecs. Please consult the supported codec list in the avconv
documentation.
@section Which codecs are supported by Windows?
.asf only
@item mpeg4
Only if you have some MPEG-4 codec like ffdshow or Xvid installed.
-@item mpeg1
+@item mpeg1video
.mpg only
@end table
Note, ASF files often have .wmv or .wma extensions in Windows. It should also
@table @option
@item adpcm_ima_wav
@item adpcm_ms
-@item pcm
+@item pcm_s16le
always
-@item mp3
+@item libmp3lame
If some MP3 codec like LAME is installed.
@end table
@chapter Usage
-@section ffmpeg does not work; what is wrong?
-
-Try a @code{make distclean} in the ffmpeg source directory before the build. If this does not help see
-(@url{http://ffmpeg.org/bugreports.html}).
-
@section How do I encode single pictures into movies?
First, rename your pictures to follow a numerical sequence.
Then you may run:
@example
- ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
+ avconv -f image2 -i img%d.jpg /tmp/a.mpg
@end example
Notice that @samp{%d} is replaced by the image number.
@file{img001.jpg}, @file{img002.jpg} and so on.
@example
- x=1; for i in *jpg; do counter=$(printf %03d $x); ln "$i" /tmp/img"$counter".jpg; x=$(($x+1)); done
+ x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s "$i" /tmp/img"$counter".jpg; x=$(($x+1)); done
@end example
If you want to sequence them by oldest modified first, substitute
Then run:
@example
- ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg
+ avconv -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg
@end example
-The same logic is used for any image format that ffmpeg reads.
+The same logic is used for any image format that avconv reads.
@section How do I encode movie to single pictures?
Use:
@example
- ffmpeg -i movie.mpg movie%d.jpg
+ avconv -i movie.mpg movie%d.jpg
@end example
The @file{movie.mpg} used as input will be converted to
Instead of relying on file format self-recognition, you may also use
@table @option
-@item -vcodec ppm
-@item -vcodec png
-@item -vcodec mjpeg
+@item -c:v ppm
+@item -c:v png
+@item -c:v mjpeg
@end table
to force the encoding.
Applying that to the previous example:
@example
- ffmpeg -i movie.mpg -f image2 -vcodec mjpeg menu%d.jpg
+ avconv -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg
@end example
Beware that there is no "jpeg" codec. Use "mjpeg" instead.
Use @file{-} as file name.
-@section Why does the chrominance data seem to be sampled at a different time from the luminance data on bt8x8 captures on Linux?
-
-This is a well-known bug in the bt8x8 driver. For 2.4.26 there is a patch at
-(@url{http://svn.ffmpeg.org/michael/trunk/patches/bttv-420-2.4.26.patch?view=co}). This may also
-apply cleanly to other 2.4-series kernels.
-
-@section How do I avoid the ugly aliasing artifacts in bt8x8 captures on Linux?
-
-Pass 'combfilter=1 lumafilter=1' to the bttv driver. Note though that 'combfilter=1'
-will cause somewhat too strong filtering. A fix is to apply (@url{http://svn.ffmpeg.org/michael/trunk/patches/bttv-comb-2.4.26.patch?view=co})
-or (@url{http://svn.ffmpeg.org/michael/trunk/patches/bttv-comb-2.6.6.patch?view=co})
-and pass 'combfilter=2'.
-
@section -f jpeg doesn't work.
Try '-f image2 test%d.jpg'.
@section Why can I not change the framerate?
Some codecs, like MPEG-1/2, only allow a small number of fixed framerates.
-Choose a different codec with the -vcodec command line option.
+Choose a different codec with the -c:v command line option.
-@section How do I encode Xvid or DivX video with ffmpeg?
+@section How do I encode Xvid or DivX video with avconv?
Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4
standard (note that there are many other coding formats that use this
-same standard). Thus, use '-vcodec mpeg4' to encode in these formats. The
+same standard). Thus, use '-c:v mpeg4' to encode in these formats. The
default fourcc stored in an MPEG-4-coded file will be 'FMP4'. If you want
a different fourcc, use the '-vtag' option. E.g., '-vtag xvid' will
force the fourcc 'xvid' to be stored as the video fourcc rather than the
default.
-@section How do I encode videos which play on the iPod?
-
-@table @option
-@item needed stuff
--acodec libfaac -vcodec mpeg4 width<=320 height<=240
-@item working stuff
-4mv, title
-@item non-working stuff
-B-frames
-@item example command line
-ffmpeg -i input -acodec libfaac -ab 128kb -vcodec mpeg4 -b 1200kb -mbd 2 -flags +4mv -trellis 2 -aic 2 -cmp 2 -subcmp 2 -s 320x180 -metadata title=X output.mp4
-@end table
-
-@section How do I encode videos which play on the PSP?
-
-@table @option
-@item needed stuff
--acodec libfaac -vcodec mpeg4 width*height<=76800 width%16=0 height%16=0 -ar 24000 -r 30000/1001 or 15000/1001 -f psp
-@item working stuff
-4mv, title
-@item non-working stuff
-B-frames
-@item example command line
-ffmpeg -i input -acodec libfaac -ab 128kb -vcodec mpeg4 -b 1200kb -ar 24000 -mbd 2 -flags +4mv -trellis 2 -aic 2 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -metadata title=X -f psp output.mp4
-@item needed stuff for H.264
--acodec libfaac -vcodec libx264 width*height<=76800 width%16=0? height%16=0? -ar 48000 -coder 1 -r 30000/1001 or 15000/1001 -f psp
-@item working stuff for H.264
-title, loop filter
-@item non-working stuff for H.264
-CAVLC
-@item example command line
-ffmpeg -i input -acodec libfaac -ab 128kb -vcodec libx264 -b 1200kb -ar 48000 -mbd 2 -coder 1 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -metadata title=X -f psp -flags loop -trellis 2 -partitions parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 output.mp4
-@item higher resolution for newer PSP firmwares, width<=480, height<=272
--vcodec libx264 -level 21 -coder 1 -f psp
-@item example command line
-ffmpeg -i input -acodec libfaac -ab 128kb -ac 2 -ar 48000 -vcodec libx264 -level 21 -b 640kb -coder 1 -f psp -flags +loop -trellis 2 -partitions +parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 -g 250 -s 480x272 output.mp4
-@end table
-
@section Which are good parameters for encoding high quality MPEG-4?
-'-mbd rd -flags +4mv+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2',
+'-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2',
things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'.
@section Which are good parameters for encoding high quality MPEG-1/MPEG-2?
but beware the '-g 100' might cause problems with some decoders.
Things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd.
-@section Interlaced video looks very bad when encoded with ffmpeg, what is wrong?
+@section Interlaced video looks very bad when encoded with avconv, what is wrong?
You should use '-flags +ilme+ildct' and maybe '-flags +alt' for interlaced
material, and try '-top 0/1' if the result looks really messed-up.
@section How can I read DirectShow files?
-If you have built FFmpeg with @code{./configure --enable-avisynth}
+If you have built Libav with @code{./configure --enable-avisynth}
(only possible on MinGW/Cygwin platforms),
then you may use any file that DirectShow can read as input.
-(Be aware that this feature has been recently added,
-so you will need to help yourself in case of problems.)
Just create an "input.avs" text file with this single line ...
@example
DirectShowSource("C:\path to your file\yourfile.asf")
@end example
-... and then feed that text file to FFmpeg:
+... and then feed that text file to avconv:
@example
- ffmpeg -i input.avs
+ avconv -i input.avs
@end example
-For ANY other help on Avisynth, please visit @url{http://www.avisynth.org/}.
+For ANY other help on AviSynth, please visit the
+@uref{http://www.avisynth.org/, AviSynth homepage}.
@section How can I join video files?
format of choice.
@example
-ffmpeg -i input1.avi -sameq intermediate1.mpg
-ffmpeg -i input2.avi -sameq intermediate2.mpg
+avconv -i input1.avi intermediate1.mpg
+avconv -i input2.avi intermediate2.mpg
cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg
-ffmpeg -i intermediate_all.mpg -sameq output.avi
+avconv -i intermediate_all.mpg output.avi
@end example
-Notice that you should either use @code{-sameq} or set a reasonably high
-bitrate for your intermediate and output files, if you want to preserve
-video quality.
+Notice that you should set a reasonably high bitrate for your intermediate and
+output files, if you want to preserve video quality.
Also notice that you may avoid the huge intermediate files by taking advantage
of named pipes, should your platform support it:
@example
mkfifo intermediate1.mpg
mkfifo intermediate2.mpg
-ffmpeg -i input1.avi -sameq -y intermediate1.mpg < /dev/null &
-ffmpeg -i input2.avi -sameq -y intermediate2.mpg < /dev/null &
+avconv -i input1.avi -y intermediate1.mpg < /dev/null &
+avconv -i input2.avi -y intermediate2.mpg < /dev/null &
cat intermediate1.mpg intermediate2.mpg |\
-ffmpeg -f mpeg -i - -sameq -vcodec mpeg4 -acodec libmp3lame output.avi
+avconv -f mpeg -i - -c:v mpeg4 -acodec libmp3lame output.avi
@end example
Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also
mkfifo temp2.v
mkfifo all.a
mkfifo all.v
-ffmpeg -i input1.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp1.a < /dev/null &
-ffmpeg -i input2.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp2.a < /dev/null &
-ffmpeg -i input1.flv -an -f yuv4mpegpipe - > temp1.v < /dev/null &
-@{ ffmpeg -i input2.flv -an -f yuv4mpegpipe - < /dev/null | tail -n +2 > temp2.v ; @} &
+avconv -i input1.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp1.a < /dev/null &
+avconv -i input2.flv -vn -f u16le -acodec pcm_s16le -ac 2 -ar 44100 - > temp2.a < /dev/null &
+avconv -i input1.flv -an -f yuv4mpegpipe - > temp1.v < /dev/null &
+@{ avconv -i input2.flv -an -f yuv4mpegpipe - < /dev/null | tail -n +2 > temp2.v ; @} &
cat temp1.a temp2.a > all.a &
cat temp1.v temp2.v > all.v &
-ffmpeg -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \
+avconv -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \
-f yuv4mpegpipe -i all.v \
- -sameq -y output.flv
+ -y output.flv
rm temp[12].[av] all.[av]
@end example
-@section FFmpeg does not adhere to the -maxrate setting, some frames are bigger than maxrate/fps.
+@section -profile option fails when encoding H.264 video with AAC audio
-Read the MPEG spec about video buffer verifier.
+@command{avconv} prints an error like
-@section I want CBR, but no matter what I do frame sizes differ.
-
-You do not understand what CBR is, please read the MPEG spec.
-Read about video buffer verifier and constant bitrate.
-The one sentence summary is that there is a buffer and the input rate is
-constant, the output can vary as needed.
+@example
+Undefined constant or missing '(' in 'baseline'
+Unable to parse option value "baseline"
+Error setting option profile to value baseline.
+@end example
-@section How do I check if a stream is CBR?
+Short answer: write @option{-profile:v} instead of @option{-profile}.
-To quote the MPEG-2 spec:
-"There is no way to tell that a bitstream is constant bitrate without
-examining all of the vbv_delay values and making complicated computations."
+Long answer: this happens because the @option{-profile} option can apply to both
+video and audio. Specifically the AAC encoder also defines some profiles, none
+of which are named @var{baseline}.
+The solution is to apply the @option{-profile} option to the video stream only
+by using @url{http://libav.org/avconv.html#Stream-specifiers-1, Stream specifiers}.
+Appending @code{:v} to it will do exactly that.
@chapter Development
-@section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?
+@section Are there examples illustrating how to use the Libav libraries, particularly libavcodec and libavformat?
-Yes. Read the Developers Guide of the FFmpeg documentation. Alternatively,
+Yes. Read the Developers Guide of the Libav documentation. Alternatively,
examine the source code for one of the many open source projects that
-already incorporate FFmpeg at (@url{projects.html}).
+already incorporate Libav at (@url{projects.html}).
@section Can you support my C compiler XXX?
@section Is Microsoft Visual C++ supported?
-No. Microsoft Visual C++ is not compliant to the C99 standard and does
-not - among other things - support the inline assembly used in FFmpeg.
-If you wish to use MSVC++ for your
-project then you can link the MSVC++ code with libav* as long as
-you compile the latter with a working C compiler. For more information, see
-the @emph{Microsoft Visual C++ compatibility} section in the FFmpeg
-documentation.
-
-There have been efforts to make FFmpeg compatible with MSVC++ in the
-past. However, they have all been rejected as too intrusive, especially
-since MinGW does the job adequately. None of the core developers
-work with MSVC++ and thus this item is low priority. Should you find
-the silver bullet that solves this problem, feel free to shoot it at us.
-
-We strongly recommend you to move over from MSVC++ to MinGW tools.
-
-@section Can I use FFmpeg or libavcodec under Windows?
-
-Yes, but the Cygwin or MinGW tools @emph{must} be used to compile FFmpeg.
-Read the @emph{Windows} section in the FFmpeg documentation to find more
-information.
-
-To get help and instructions for building FFmpeg under Windows, check out
-the FFmpeg Windows Help Forum at
-@url{http://ffmpeg.arrozcru.org/}.
+Yes. Please see the @uref{platform.html, Microsoft Visual C++}
+section in the Libav documentation.
@section Can you add automake, libtool or autoconf support?
No. These tools are too bloated and they complicate the build.
-@section Why not rewrite ffmpeg in object-oriented C++?
+@section Why not rewrite Libav in object-oriented C++?
-FFmpeg is already organized in a highly modular manner and does not need to
+Libav is already organized in a highly modular manner and does not need to
be rewritten in a formal object language. Further, many of the developers
favor straight C; it works for them. For more arguments on this matter,
-read "Programming Religion" at (@url{http://www.tux.org/lkml/#s15}).
-
-@section Why are the ffmpeg programs devoid of debugging symbols?
-
-The build process creates ffmpeg_g, ffplay_g, etc. which contain full debug
-information. Those binaries are stripped to create ffmpeg, ffplay, etc. If
-you need the debug information, used the *_g versions.
+read @uref{http://www.tux.org/lkml/#s15, "Programming Religion"}.
@section I do not like the LGPL, can I contribute code under the GPL instead?
under #if CONFIG_GPL without breaking anything. So for example a new codec
or filter would be OK under GPL while a bug fix to LGPL code would not.
-@section I want to compile xyz.c alone but my compiler produced many errors.
-
-Common code is in its own files in libav* and is used by the individual
-codecs. They will not work without the common parts, you have to compile
-the whole libav*. If you wish, disable some parts with configure switches.
-You can also try to hack it and remove more, but if you had problems fixing
-the compilation failure then you are probably not qualified for this.
-
-@section I'm using libavcodec from within my C++ application but the linker complains about missing symbols which seem to be available.
+@section I'm using Libav from within my C++ application but the linker complains about missing symbols which seem to be available.
-FFmpeg is a pure C project, so to use the libraries within your C++ application
+Libav is a pure C project, so to use the libraries within your C++ application
you need to explicitly state that you are using a C library. You can do this by
-encompassing your FFmpeg includes using @code{extern "C"}.
+encompassing your Libav includes using @code{extern "C"}.
See @url{http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3}
-@section I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?
-
-You have to implement a URLProtocol, see libavformat/file.c in FFmpeg
-and libmpdemux/demux_lavf.c in MPlayer sources.
-
-@section I get "No compatible shell script interpreter found." in MSys.
-
-The standard MSys bash (2.04) is broken. You need to install 2.05 or later.
-
-@section I get "./configure: line <xxx>: pr: command not found" in MSys.
+@section I'm using libavutil from within my C++ application but the compiler complains about 'UINT64_C' was not declared in this scope
-The standard MSys install doesn't come with pr. You need to get it from the coreutils package.
+Libav is a pure C project using C99 math features, in order to enable C++
+to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS
-@section I tried to pass RTP packets into a decoder, but it doesn't work.
-
-RTP is a container format like any other, you must first depacketize the
-codec frames/samples stored in RTP and then feed to the decoder.
-
-@section Where can I find libav* headers for Pascal/Delphi?
-
-see @url{http://www.iversenit.dk/dev/ffmpeg-headers/}
-
-@section Where is the documentation about ffv1, msmpeg4, asv1, 4xm?
+@section I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?
-see @url{http://svn.ffmpeg.org/michael/trunk/docs/}
+You have to create a custom AVIOContext using @code{avio_alloc_context},
+see @file{libavformat/aviobuf.c} in Libav and @file{libmpdemux/demux_lavf.c} in MPlayer2 sources.
-@section How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?
+@section Why is @code{make fate} not running all tests?
-Even if peculiar since it is network oriented, RTP is a container like any
-other. You have to @emph{demux} RTP before feeding the payload to libavcodec.
-In this specific case please look at RFC 4629 to see how it should be done.
+Make sure you have the fate-suite samples and the @code{SAMPLES} Make variable
+or @code{FATE_SAMPLES} environment variable or the @code{--samples}
+@command{configure} option is set to the right path.
-@section AVStream.r_frame_rate is wrong, it is much larger than the framerate.
+@section Why is @code{make fate} not finding the samples?
-r_frame_rate is NOT the average framerate, it is the smallest framerate
-that can accurately represent all timestamps. So no, it is not
-wrong if it is larger than the average!
-For example, if you have mixed 25 and 30 fps content, then r_frame_rate
-will be 150.
+Do you happen to have a @code{~} character in the samples path to indicate a
+home directory? The value is used in ways where the shell cannot expand it,
+causing FATE to not find files. Just replace @code{~} by the full path.
@bye
projects / ffmpeg / blobdiff