codecs. Please consult the supported codec list in the ffmpeg
documentation.
-@section How do I encode JPEGs to another format ?
+@section How do I encode single pictures to movies?
-If the JPEGs are named img1.jpg, img2.jpg, img3.jpg,..., use:
+First, rename your pictures to follow a numerical sequence.
+For example, img1.jpg, img2.jpg, img3.jpg,...
+Then you may run:
@example
ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
@end example
-@samp{%d} is replaced by the image number.
+Notice that @samp{%d} is replaced by the image number.
-@file{img%03d.jpg} generates @file{img001.jpg}, @file{img002.jpg}, etc...
+@file{img%03d.jpg} means the sequence @file{img001.jpg}, @file{img002.jpg}, etc...
-The same system is used for the other image formats.
+The same logic is used for any image format that ffmpeg reads.
-@section How do I encode movie to single pictures ?
+@section How do I encode movie to single pictures?
Use:
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 ?
+@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 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 ?
+@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 ?
+@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 ?
+@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
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
install some additional codecs
@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
+(@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://mplayerhq.hu/~michael/bttv-comb-2.4.26.patch})
-or (@url{http://mplayerhq.hu/~michael/bttv-comb-2.6.6.patch})
+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?
@section ffmpeg does not work; What is wrong?
Try a 'make distclean' in the ffmpeg source directory before the build. If this does not help see
-(@url{http://ffmpeg.org/bugreports.php}).
+(@url{http://ffmpeg.org/bugreports.html}).
@section How do I encode XviD or DivX video with ffmpeg?
@table @option
@item needed stuff
--acodec aac -vcodec mpeg4 width<=320 height<=240
+-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 aac -ab 128 -vcodec mpeg4 -b 1200kb -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -s 320x180 -title X output.mp4
+ffmpeg -i input -acodec libfaac -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
+-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 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
+ffmpeg -i input -acodec libfaac -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
+-acodec libfaac -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
+ffmpeg -i input -acodec libfaac -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
@section Which are good parameters for encoding high quality MPEG-4?
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
+
+@section How can I join video files?
+
+A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow to join video files by
+merely concatenating 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.
+
+@example
+ffmpeg -i input1.avi -sameq intermediate1.mpg
+ffmpeg -i input2.avi -sameq intermediate2.mpg
+cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg
+ffmpeg -i intermediate_all.mpg -sameq 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.
+
+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 &
+cat intermediate1.mpg intermediate2.mpg |\
+ffmpeg -f mpeg -i - -sameq -vcodec mpeg4 -acodec libmp3lame output.avi
+@end example
+
+Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also
+allow concatenation, and the transcoding step is almost lossless.
+
+For example, let's say we want to join two FLV files into an output.flv file:
+
+@example
+mkfifo temp1.a
+mkfifo temp1.v
+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 - > temp2.v < /dev/null &
+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 \
+ -f yuv4mpegpipe -i all.v \
+ -sameq -y output.flv
+rm temp[12].[av] all.[av]
+@end example
+
+@section Is there a forum for FFmpeg? I do not like mailing lists.
+
+Yes, (@url{http://dir.gmane.org/gmane.comp.video.ffmpeg.user}).
+
+@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 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.
+
+@section How do I check if a stream is CBR?
+
+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."
+
+
@chapter Development
@section When will the next FFmpeg version be released? / Why are FFmpeg releases so few and far between?
it implemented is to undertake the task yourself.
-@section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat ?
+@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}).
+already incorporate ffmpeg at (@url{projects.html}).
-@section Can you support my C compiler XXX ?
+@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 Visual C++ produces many errors.
+@section Microsoft Visual C++ produces many errors.
-Visual C++ is not compliant to the C standard and does not support
+Microsoft 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
+If you wish - for whatever weird reason - 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{Visual C++ compatibility} section in the FFmpeg documentation.
+the @emph{Microsoft Visual C++ compatibility} section in the FFmpeg
+documentation.
-There have been efforts to make FFmpeg compatible with Visual C++ in the
+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 perfectly adequately. None of the core developers
-work with Visual C++ and thus this item is low priority. Should you find
+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.
-@section Can I use FFmpeg or libavcodec under Windows ?
+@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.
+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 using FFmpeg under Windows, check out
+To get help and instructions for building 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 ?
+@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 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 ?
+@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 ?
+@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
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 ?
+@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
+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"}.
+
+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.
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.
+
+The standard MSys install doesn't come with pr. You need to get it from the coreutils package.
+
@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.
+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?
+
+see @url{http://svn.mplayerhq.hu/michael/trunk/docs/}
+
+@section How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?
+
+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.
+
+@section AVStream.r_frame_rate is wrong, it is much larger than the framerate.
+
+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.
@bye
projects / ffmpeg / blobdiff