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@settitle FFmpeg FAQ
@titlepage
@sp 7
@center @titlefont{FFmpeg FAQ}
@sp 3
@end titlepage


@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.

@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 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 or sponsor a developer.

@section FFmpeg 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.
A DLL loader is not conducive to that goal.

@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 Is there a forum for FFmpeg? I do not like mailing lists.

Yes, (@url{http://dir.gmane.org/gmane.comp.video.ffmpeg.user}).

@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
documentation.

@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


@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 to movies?

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

Notice that @samp{%d} is replaced by the image number.

@file{img%03d.jpg} means the sequence @file{img001.jpg}, @file{img002.jpg}, etc...

The same logic is used for any image format that ffmpeg reads.

@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 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 AC-3 (a.k.a. A/52). AC-3 decoding is an optional component in FFmpeg
as the component that handles AC-3 decoding is currently released under the GPL.
Enable AC-3 decoding with @code{./configure --enable-gpl}. Take care: By
enabling AC-3, you automatically change the license of libavcodec from
LGPL to GPL.

@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 -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 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 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+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 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+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 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