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diff --git a/contrib/ffmpeg/doc/faq.texi b/contrib/ffmpeg/doc/faq.texi new file mode 100644 index 000000000..9f1e8ec2d --- /dev/null +++ b/contrib/ffmpeg/doc/faq.texi @@ -0,0 +1,312 @@ +\input texinfo @c -*- texinfo -*- + +@settitle FFmpeg FAQ +@titlepage +@sp 7 +@center @titlefont{FFmpeg FAQ} +@sp 3 +@end titlepage + + +@chapter General Problems + +@section I cannot read this file although this format seems to be supported by ffmpeg. + +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 ? + +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. + +@section How can I read from the standard input or write to the standard output ? + +Use @file{-} as filename. + +@section Why does ffmpeg not decode audio in VOB files ? + +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-a52}. Take care: by +enabling AC3, you automatically change the license of libavcodec from +LGPL to GPL. + +@section Which codecs are supported by Windows ? + +Windows does not support standard formats like MPEG very well, unless you +install some additional codecs + +The following list of video codecs should work on most Windows systems: +@table @option +@item msmpeg4v2 +.avi/.asf +@item msmpeg4 +.asf only +@item wmv1 +.asf only +@item wmv2 +.asf only +@item mpeg4 +only if you have some MPEG-4 codec installed like ffdshow or XviD +@item mpeg1 +.mpg only +@end table +Note, ASF files often have .wmv or .wma extensions in Windows. It should also +be mentioned that Microsoft claims a patent on the ASF format, and may sue +or threaten users who create ASF files with non-Microsoft software. It is +strongly advised to avoid ASF where possible. + +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 +@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. + +@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://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'. + +@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". + +@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. + +@section ffmpeg does not work; What is wrong? + +Try a 'make distclean' in the ffmpeg source directory. If this does not help see +(@url{http://ffmpeg.org/bugreports.php}). + +@section How do I encode XviD or DivX video with ffmpeg? + +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 +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 How can I read DirectShow files? + +If you have built FFmpeg 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: +@example + ffmpeg -i input.avs +@end example + +For ANY other help on Avisynth, please visit @url{http://www.avisynth.org/}. + +@chapter Development + +@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. + +@section Why doesn't FFmpeg support feature [xyz]? + +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. + + +@section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat ? + +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}). + +@section Can you support my C compiler XXX ? + +No. Only GCC is supported. GCC is ported to most systems available and there +is no need to pollute the source code with @code{#ifdef}s +related to the compiler. + +@section Can I use FFmpeg or libavcodec under Windows ? + +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. + +@section Can you add automake, libtool or autoconf support ? + +No. These tools are too bloated and they complicate the build. Moreover, +since only @samp{gcc} is supported they would add little advantages in +terms of portability. + +@section Why not rewrite ffmpeg in object-oriented C++ ? + +ffmpeg 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://lkml.org/faq/lkmlfaq-15.html}). + +@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 strip'd to create ffmpeg, ffplay, etc. If +you need the debug information, used the *_g versions. + +@section I do not like the LGPL, can I contribute code under the GPL instead ? + +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. + +@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 Visual C++ produces many errors. + +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. + +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. + +@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. + +@bye |