X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=doc%2Ffaq.texi;h=b400124f694152bb2509d1f158f707eb0e49762a;hb=f912fd767e55bbb5a1554bd99bacab007659609c;hp=71a5b9ea1bce9f524d2d3404d2495410850800be;hpb=123bff4bf16cc315fb81de5eb92d24db404bb367;p=ffmpeg diff --git a/doc/faq.texi b/doc/faq.texi index 71a5b9ea1bc..b400124f694 100644 --- a/doc/faq.texi +++ b/doc/faq.texi @@ -1,93 +1,39 @@ \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 Problems +@contents -@section I cannot read this file although this format seems to be supported by ffmpeg. +@chapter General Questions -Even if ffmpeg can read the file format, it may not support all its -codecs. Please consult the supported codec list in the ffmpeg -documentation. - -@section How do I encode JPEGs to another format ? - -If the JPEGs are named img1.jpg, img2.jpg, img3.jpg,..., use: - -@example - ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg -@end example - -@samp{%d} is replaced by the image number. - -@file{img%03d.jpg} generates @file{img001.jpg}, @file{img002.jpg}, etc... - -The same system is used for the other image formats. - -@section How do I encode movie to single pictures ? - -Use: - -@example - ffmpeg -i movie.mpg movie%d.jpg -@end example - -The @file{movie.mpg} used as input will be converted to -@file{movie1.jpg}, @file{movie2.jpg}, etc... - -Instead of relying on file format self-recognition, you may also use -@table @option -@item -vcodec ppm -@item -vcodec png -@item -vcodec 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 -@end example - -Beware that there is no "jpeg" codec. Use "mjpeg" instead. - -@section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it ? - -No. FFmpeg only supports open source codecs. Windows DLLs are not -portable, bloated and often slow. - -@section I get "Unsupported codec (id=86043) for input stream #0.1". What is the problem ? +@section Why doesn't Libav support feature [xyz]? -This is the Qcelp codec, FFmpeg has no support for that codec currently. Try mencoder/mplayer it might work. - -@section Why do I see a slight quality degradation with multithreaded MPEG* encoding ? - -For multithreaded MPEG* encoding, the encoded slices must be independent, -otherwise thread n would practically have to wait for n-1 to finish, so it's -quite logical that there is a small reduction of quality. This is not a bug. +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 How can I read from the standard input or write to the standard output ? +@section Libav does not support codec XXX. Can you include a Windows DLL loader to support it? -Use @file{-} as filename. +No. Windows DLLs are not portable, bloated and often slow. +Moreover Libav strives to support all codecs natively. +A DLL loader is not conducive to that goal. -@section Why does ffmpeg not decode audio in VOB files ? +@section I cannot read this file although this format seems to be supported by avconv. -The audio is AC3 (a.k.a. A/52). AC3 decoding is an optional component in ffmpeg -as the component that handles AC3 decoding (liba52) is currently released under -the GPL. If you have liba52 installed on your system, enable AC3 decoding -with @code{./configure --enable-liba52 --enable-gpl}. Take care: by -enabling AC3, you automatically change the license of libavcodec from -LGPL to GPL. +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 ? +@section Which codecs are supported by Windows? Windows does not support standard formats like MPEG very well, unless you -install some additional codecs +install some additional codecs. The following list of video codecs should work on most Windows systems: @table @option @@ -100,8 +46,8 @@ The following list of video codecs should work on most Windows systems: @item wmv2 .asf only @item mpeg4 -only if you have some MPEG-4 codec installed like ffdshow or XviD -@item mpeg1 +Only if you have some MPEG-4 codec like ffdshow or Xvid installed. +@item mpeg1video .mpg only @end table Note, ASF files often have .wmv or .wma extensions in Windows. It should also @@ -113,29 +59,98 @@ The following list of audio codecs should work on most Windows systems: @table @option @item adpcm_ima_wav @item adpcm_ms -@item pcm -@item mp3 -if some MP3 codec like LAME is installed +@item pcm_s16le +always +@item libmp3lame +If some MP3 codec like LAME is installed. @end table -@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://mplayerhq.hu/~michael/bttv-420-2.4.26.patch}). This may also -apply cleanly to other 2.4-series kernels. +@chapter Compilation + +@section @code{error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'} + +This is a bug in gcc. Do not report it to us. Instead, please report it to +the gcc developers. Note that we will not add workarounds for gcc bugs. + +Also note that (some of) the gcc developers believe this is not a bug or +not a bug they should fix: +@url{http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203}. +Then again, some of them do not know the difference between an undecidable +problem and an NP-hard problem... + +@chapter Usage + +@section How do I encode single pictures into movies? + +First, rename your pictures to follow a numerical sequence. +For example, img1.jpg, img2.jpg, img3.jpg,... +Then you may run: + +@example + avconv -f image2 -i img%d.jpg /tmp/a.mpg +@end example + +Notice that @samp{%d} is replaced by the image number. + +@file{img%03d.jpg} means the sequence @file{img001.jpg}, @file{img002.jpg}, etc... + +If you have large number of pictures to rename, you can use the +following command to ease the burden. The command, using the bourne +shell syntax, symbolically links all files in the current directory +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 $x); ln -s "$i" /tmp/img"$counter".jpg; x=$(($x+1)); done +@end example + +If you want to sequence them by oldest modified first, substitute +@code{$(ls -r -t *jpg)} in place of @code{*jpg}. -@section How do I avoid the ugly aliasing artifacts in bt8x8 captures on Linux? +Then run: -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://mplayerhq.hu/~michael/bttv-comb-2.4.26.patch}) -or (@url{http://mplayerhq.hu/~michael/bttv-comb-2.6.6.patch}) -and pass 'combfilter=2'. +@example + avconv -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg +@end example + +The same logic is used for any image format that avconv reads. + +@section How do I encode movie to single pictures? -@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". +Use: + +@example + avconv -i movie.mpg movie%d.jpg +@end example + +The @file{movie.mpg} used as input will be converted to +@file{movie1.jpg}, @file{movie2.jpg}, etc... + +Instead of relying on file format self-recognition, you may also use +@table @option +@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 + avconv -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg +@end example + +Beware that there is no "jpeg" codec. Use "mjpeg" instead. + +@section Why do I see a slight quality degradation with multithreaded MPEG* encoding? + +For multithreaded MPEG* encoding, the encoded slices must be independent, +otherwise thread n would practically have to wait for n-1 to finish, so it's +quite logical that there is a small reduction of quality. This is not a bug. + +@section How can I read from the standard input or write to the standard output? + +Use @file{-} as file name. @section -f jpeg doesn't work. @@ -144,187 +159,196 @@ 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. - -@section ffmpeg does not work; What is wrong? +Choose a different codec with the -c:v command line option. -Try a 'make distclean' in the ffmpeg source directory before the build. If this does not help see -(@url{http://ffmpeg.org/bugreports.php}). +@section How do I encode Xvid or DivX video with avconv? -@section How do I encode XviD or DivX video with ffmpeg? - -Both XviD and DivX (version 4+) are implementations of the ISO MPEG-4 +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 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 aac -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 aac -ab 128 -vcodec mpeg4 -b 1200kb -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -s 320x180 -title X output.mp4 -@end table - -@section How do I encode videos which play on the PSP? - -@table @option -@item needed stuff --acodec aac -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 aac -ab 128 -vcodec mpeg4 -b 1200kb -ar 24000 -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -title X -f psp output.mp4 -@item needed stuff for H.264 --acodec aac -vcodec h264 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 aac -ab 128 -vcodec h264 -b 1200kb -ar 48000 -mbd 2 -coder 1 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -title X -f psp -flags loop -trellis 2 -partitions parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 output.mp4 -@end table - @section Which are good parameters for encoding high quality MPEG-4? -'-mbd rd -flags +4mv+trell+aic -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? -'-mbd rd -flags +trell -cmp 2 -subcmp 2 -g 100 -pass 1/2' +'-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2' 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, whats 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}. -@chapter Development +@section How can I join video files? -@section When will the next FFmpeg version be released? / Why are FFmpeg releases so few and far between? +A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow to join video files by +merely concatenating them. -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. +Hence you may concatenate your multimedia files by first transcoding them to +these privileged formats, then using the humble @code{cat} command (or the +equally humble @code{copy} under Windows), and finally transcoding back to your +format of choice. -@section Why doesn't FFmpeg support feature [xyz]? +@example +avconv -i input1.avi intermediate1.mpg +avconv -i input2.avi intermediate2.mpg +cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg +avconv -i intermediate_all.mpg output.avi +@end example -Because no one has taken on that task yet. FFmpeg 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. +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: -@section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat ? +@example +mkfifo intermediate1.mpg +mkfifo intermediate2.mpg +avconv -i input1.avi -y intermediate1.mpg < /dev/null & +avconv -i input2.avi -y intermediate2.mpg < /dev/null & +cat intermediate1.mpg intermediate2.mpg |\ +avconv -f mpeg -i - -c:v mpeg4 -acodec libmp3lame output.avi +@end example -Yes. Read the Developers Guide of the FFmpeg documentation. Alternatively, -examine the source code for one of the many open source projects that -already incorporate ffmpeg at (@url{projects.php}). +Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also +allow concatenation, and the transcoding step is almost lossless. +When using multiple yuv4mpegpipe(s), the first line needs to be discarded +from all but the first stream. This can be accomplished by piping through +@code{tail} as seen below. Note that when piping through @code{tail} you +must use command grouping, @code{@{ ;@}}, to background properly. -@section Can you support my C compiler XXX ? +For example, let's say we want to join two FLV files into an output.flv file: -It depends. If your compiler is C99-compliant, then patches to support -it are likely to be welcome if they do not pollute the source code -with @code{#ifdef}s related to the compiler. +@example +mkfifo temp1.a +mkfifo temp1.v +mkfifo temp2.a +mkfifo temp2.v +mkfifo all.a +mkfifo all.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 & +avconv -f u16le -acodec pcm_s16le -ac 2 -ar 44100 -i all.a \ + -f yuv4mpegpipe -i all.v \ + -y output.flv +rm temp[12].[av] all.[av] +@end example -@section Visual C++ produces many errors. +@section -profile option fails when encoding H.264 video with AAC audio -Visual C++ is not compliant to the C standard and does not support -the inline assembly used in FFmpeg. -If you wish - for whatever weird reason - to use Visual C++ for your -project then you can link the Visual C++ code with libav* as long as -you compile the latter with a working C compiler. For more information, see -the @emph{Visual C++ compatibility} section in the FFmpeg documentation. +@command{avconv} prints an error like -There have been efforts to make FFmpeg compatible with Visual C++ in the -past. However, they have all been rejected as too intrusive, especially -since MinGW does the job perfectly adequately. None of the core developers -work with Visual C++ and thus this item is low priority. Should you find -the silver bullet that solves this problem, feel free to shoot it at us. +@example +Undefined constant or missing '(' in 'baseline' +Unable to parse option value "baseline" +Error setting option profile to value baseline. +@end example -@section Can I use FFmpeg or libavcodec under Windows ? +Short answer: write @option{-profile:v} instead of @option{-profile}. -Yes, but the MinGW tools @emph{must} be used to compile FFmpeg. You -can link the resulting DLLs with any other Windows program. Read the -@emph{Native Windows Compilation} and @emph{Visual C++ compatibility} -sections in the FFmpeg documentation to find more information. +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}. -To get help and instructions for using FFmpeg under Windows, check out -the FFmpeg Windows Help Forum at -@url{http://arrozcru.no-ip.org/ffmpeg/}. +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 Can you add automake, libtool or autoconf support ? +@section Are there examples illustrating how to use the Libav libraries, particularly libavcodec and libavformat? + +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 Libav at (@url{projects.html}). + +@section Can you support my C compiler XXX? + +It depends. If your compiler is C99-compliant, then patches to support +it are likely to be welcome if they do not pollute the source code +with @code{#ifdef}s related to the compiler. + +@section Is Microsoft Visual C++ supported? + +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}). +read @uref{http://www.tux.org/lkml/#s15, "Programming Religion"}. -@section Why are the ffmpeg programs devoid of debugging symbols ? +@section I do not like the LGPL, can I contribute code under the GPL instead? -The build process creates ffmpeg_g, ffplay_g, etc. which contain full debug -information. Those binaries are strip'd to create ffmpeg, ffplay, etc. If -you need the debug information, used the *_g versions. +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 do not like the LGPL, can I contribute code under the GPL instead ? +@section I'm using Libav from within my C++ application but the linker complains about missing symbols which seem to be available. -Yes, as long as the code is optional and can easily and cleanly be placed -under #ifdef CONFIG_GPL without breaking anything. So for example a new codec -or filter would be OK under GPL while a bugfix to LGPL code would not. +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 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'm using libavutil from within my C++ application but the compiler complains about 'UINT64_C' was not declared in this scope + +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 want to compile xyz.c alone but my compiler produced many errors. +@section I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat? -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. +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 I have a file in memory / a API different from *open/*read/ libc how do i use it with libavformat ? +@section Why is @code{make fate} not running all tests? -You have to implement a URLProtocol, see libavformat/file.c in FFmpeg -and libmpdemux/demux_lavf.c in MPlayer sources. +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 I get "No compatible shell script interpreter found." in MSys. +@section Why is @code{make fate} not finding the samples? -The standard MSys bash (2.04) is broken. You need to install 2.05 or later. +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