X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=doc%2Ffaq.texi;h=b400124f694152bb2509d1f158f707eb0e49762a;hb=5c08ae4f37281441188447cd04dcaf7cd7ce031f;hp=6229666f208f50089bc1e0b4d9e7d759e489d2dc;hpb=e7f6c252a247688c6b68429d084a3573aa6800a4;p=ffmpeg diff --git a/doc/faq.texi b/doc/faq.texi index 6229666f208..b400124f694 100644 --- a/doc/faq.texi +++ b/doc/faq.texi @@ -1,71 +1,33 @@ \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? @@ -85,7 +47,7 @@ The following list of video codecs should work on most Windows systems: .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 @@ -97,9 +59,9 @@ The following list of audio codecs should work on most Windows systems: @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 @@ -119,11 +81,6 @@ problem and an NP-hard problem... @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. @@ -131,7 +88,7 @@ For example, img1.jpg, img2.jpg, img3.jpg,... 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. @@ -145,7 +102,7 @@ that match @code{*jpg} to the @file{/tmp} directory in the sequence of @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 @@ -154,17 +111,17 @@ 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 @@ -172,15 +129,15 @@ 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. @@ -195,19 +152,6 @@ quite logical that there is a small reduction of quality. This is not a bug. 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'. @@ -215,59 +159,21 @@ 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? @@ -276,14 +182,14 @@ things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'. 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. @@ -291,12 +197,13 @@ 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? @@ -309,15 +216,14 @@ equally humble @code{copy} under Windows), and finally transcoding back to your 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: @@ -325,10 +231,10 @@ 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 @@ -347,43 +253,45 @@ mkfifo temp2.a 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. - -Read the MPEG spec about video buffer verifier. +@section -profile option fails when encoding H.264 video with AAC audio -@section I want CBR, but no matter what I do frame sizes differ. +@command{avconv} prints an error like -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? @@ -393,48 +301,19 @@ with @code{#ifdef}s related to the compiler. @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? @@ -442,55 +321,34 @@ Yes, as long as the code is optional and can easily and cleanly be placed 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. +@section I'm using Libav from within my C++ application but the linker complains about missing symbols which seem to be available. -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. - -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 @file{libavformat/file.c} in -FFmpeg and @file{libmpdemux/demux_lavf.c} in MPlayer sources. - -@section I get "No compatible shell script interpreter 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 bash (2.04) is broken. You need to install 2.05 or later. +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 get "./configure: line : pr: command not found" in MSys. - -The standard MSys install doesn't come with pr. You need to get it from the coreutils package. - -@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://www.ffmpeg.org/~michael/} +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