@chapter General Problems
-@section ffserver doesn't not work.
-
-ffmpeg development is now concentrated on the codec and format
-handling. New developments broke ffserver, so don't expect it to work
-correctly. It is planned to fix it ASAP.
-
-@section I cannot read this file although this format seems to be suppored by ffmpeg.
+@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 I get audio/video synchro problems when grabbing.
-
-Currently, the grabbing stuff does not handle synchronisation
-correctly. You are free to correct it. It is planned to fix it ASAP.
+@section How do I encode JPEGs to another format ?
-@section How do I encode jpegs to another format ?
-
-If the jpegs are named img1.jpg, img2.jpg, img3.jpg,..., use:
+If the JPEGs are named img1.jpg, img2.jpg, img3.jpg,..., use:
@example
- ffmpeg -i img%d.jpg /tmp/a.mpg
+ ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
@end example
@samp{%d} is replaced by the image number.
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 Audio is not decoded in VOB files ?
+@section Why does ffmpeg not decode audio in VOB files ?
-AC3 decoding is optional as the codec is currently released under the
-GPL. Enable it with @code{./configure --enable-a52}. Take care: by
+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.
-@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
+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
+The following list of video codecs should work on most Windows systems:
@table @option
@item msmpeg4v2
.avi/.asf
@item wmv2
.asf only
@item mpeg4
-only if you have some mpeg4 codec installed like ffdshow or xvid
+only if you have some MPEG-4 codec installed like ffdshow or XviD
@item mpeg1
.mpg only
@end table
-note, asf often uses .wmv or .wma extensions in windows, it should also be
-mentioned that asf is patented, so microsoft may sue or threaten users who
-use it if they see any reason to do so, it is strongly recommanded to avoid asf
-for any use
+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
+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
+if some MP3 codec like LAME is installed
@end table
-@section The chrominance seems to come from a different time then the luminance on bt8x8 captures on linux?
+@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.mplayerhq.hu/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.mplayerhq.hu/michael/trunk/patches/bttv-comb-2.4.26.patch?view=co})
+or (@url{http://svn.mplayerhq.hu/michael/trunk/patches/bttv-comb-2.6.6.patch?view=co})
+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?
-well known bug in the bt8x8 driver, for 2.4.26 theres a patch at
-(@url{http://www.mplayerhq.hu/~michael/bttv-420-2.4.26.patch}), i suspect that
-this will also apply cleanly to other 2.4 kernels
+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 to avoid the ugly aliassing artefacts in bt8x8 captures on linux?
+@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 128kb -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 128kb -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 128kb -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
-pass 'combfilter=1 lumafilter=1' to the bttv driver, note though that 'combfilter=1'
-will cause somewhat too strong filtering, a fix is too apply (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.4.26.patch})
-or (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.6.6.patch})
-and pass 'combfilter=2'
+@section Which are good parameters for encoding high quality MPEG-4?
-@section -f jpeg doesnt work.
+'-mbd rd -flags +4mv+trell+aic -cmp 2 -subcmp 2 -g 300 -pass 1/2',
+things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'.
-try '-f image -img jpeg test%d.jpg'
+@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'
+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?
+
+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}
+(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/}.
+
+@section My bugreport/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
@chapter Development
-@section Are there examples of use of the FFmpeg libraries libavcodec and libavformat ?
+@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.
+
-Yes. Read the Developers Guide of the FFmpeg documentation.
+@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 on most systems available and I
-don't see the need to pollute the source code with @code{#ifdef}s
-related to the compiler.
+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 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 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} section in the FFmpeg documentation
-to have more information.
+@emph{Native Windows Compilation} and @emph{Visual C++ compatibility}
+sections in the FFmpeg documentation to find more information.
+
+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/}.
@section Can you add automake, libtool or autoconf support ?
-No. These tools are too blowted and they complicate the build. Moreover,
-since only @samp{gcc} is supported they would add little advantages in
-terms of portability.
+No. These tools are too bloated and they complicate the build.
+
+@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://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 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 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 tried to pass RTP packets into a decoder, but it doesn't work.
+
+Of course not, you MUST strip ALL RTP headers and assemble valid packets
+first, an MP3 decoder decodes MP3 packets not bastardized MP3 packets
+encapsulated in RTP. The same applies to all decoders, this is not specific
+to ffmpeg or libavcodec.
+
+@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?
+
+see @url{http://svn.mplayerhq.hu/michael/trunk/docs/}
@bye
projects / ffmpeg / blobdiff