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158 lines
5.0 KiB
Plaintext
158 lines
5.0 KiB
Plaintext
\input texinfo @c -*- texinfo -*-
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@settitle FFmpeg FAQ
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@titlepage
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@sp 7
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@center @titlefont{FFmpeg FAQ}
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@sp 3
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@end titlepage
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@chapter General Problems
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@section ffserver doesn't not work.
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ffmpeg development is now concentrated on the codec and format
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handling. New developments broke ffserver, so don't expect it to work
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correctly. If you have time and experience, please help us fix it.
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@section I cannot read this file although this format seems to be suppored by ffmpeg.
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Even if ffmpeg can read the file format, it may not support all its
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codecs. Please consult the supported codec list in the ffmpeg
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documentation.
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@section I get audio/video synchro problems when grabbing.
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Currently, the grabbing stuff does not handle synchronisation
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correctly. You are free to correct it. It is planned to fix it ASAP.
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@section How do I encode jpegs to another format ?
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If the jpegs are named img1.jpg, img2.jpg, img3.jpg,..., use:
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@example
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ffmpeg -i img%d.jpg /tmp/a.mpg
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@end example
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@samp{%d} is replaced by the image number.
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@file{img%03d.jpg} generates @file{img001.jpg}, @file{img002.jpg}, etc...
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The same system is used for the other image formats.
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@section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it ?
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No. FFmpeg only supports open source codecs. Windows DLLs are not
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portable, bloated and often slow.
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@section Why do I see a slight quality degradation with multithreaded MPEG* encoding ?
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For multithreaded MPEG* encoding, the encoded slices must be independent,
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otherwise thread n would practically have to wait for n-1 to finish, so its
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quite logic that there is a small reduction of quality, this is not a bug
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@section How can I read from the standard input or write to the standard output ?
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Use @file{-} as filename.
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@section Why Audio is not decoded in VOB files ?
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AC3 decoding is optional as the codec is currently released under the
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GPL. Enable it with @code{./configure --enable-a52}. Take care: by
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enabling AC3, you automatically change the license of libavcodec from
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LGPL to GPL.
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@section Which codecs are supported by windows ?
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Windows does not support standard formats like mpeg very well, unless you
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install some additional codecs
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The following list of video codecs should work on most windows systems
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@table @option
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@item msmpeg4v2
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.avi/.asf
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@item msmpeg4
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.asf only
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@item wmv1
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.asf only
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@item wmv2
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.asf only
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@item mpeg4
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only if you have some mpeg4 codec installed like ffdshow or xvid
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@item mpeg1
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.mpg only
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@end table
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note, asf often uses .wmv or .wma extensions in windows, it should also be
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mentioned that asf is patented, so microsoft may sue or threaten users who
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use it if they see any reason to do so, it is strongly recommanded to avoid asf
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for any use
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The following list of audio codecs should work on most windows systems
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@table @option
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@item adpcm_ima_wav
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@item adpcm_ms
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@item pcm
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@item mp3
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if some mp3 codec like lame is installed
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@end table
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@section The chrominance seems to come from a different time then the luminance on bt8x8 captures on linux?
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well known bug in the bt8x8 driver, for 2.4.26 theres a patch at
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(@url{http://www.mplayerhq.hu/~michael/bttv-420-2.4.26.patch}), i suspect that
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this will also apply cleanly to other 2.4 kernels
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@section How to avoid the ugly aliassing artefacts in bt8x8 captures on linux?
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pass 'combfilter=1 lumafilter=1' to the bttv driver, note though that 'combfilter=1'
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will cause somewhat too strong filtering, a fix is too apply (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.4.26.patch})
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or (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.6.6.patch})
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and pass 'combfilter=2'
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@section I have a problem with an old version of ffmpeg, where should i report it?
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Nowhere, upgrade to the latest release or if there is no recent release upgrade
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to cvs, you could also try to report it, maybe you are lucky and
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will become the first person in history to get a different awnser from "upgrade
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to cvs".
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@section -f jpeg doesnt work.
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try '-f image -img jpeg test%d.jpg'
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@section i cant change the framerate
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some codecs, like mpeg1/2 only allow a small number of fixed framerates,
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choose a different codec with -vcodec
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@chapter Development
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@section Are there examples of use of the FFmpeg libraries libavcodec and libavformat ?
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Yes. Read the Developers Guide of the FFmpeg documentation.
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@section Can you support my C compiler XXX ?
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No. Only GCC is supported. GCC is ported on most systems available and I
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don't see the need to pollute the source code with @code{#ifdef}s
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related to the compiler.
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@section Can I use FFmpeg or libavcodec under Windows ?
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Yes, but the MinGW tools @emph{must} be used to compile FFmpeg. You
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can link the resulting DLLs with any other Windows program. Read the
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@emph{Native Windows Compilation} section in the FFmpeg documentation
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to have more information.
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@section Can you add automake, libtool or autoconf support ?
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No. These tools are too blowted and they complicate the build. Moreover,
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since only @samp{gcc} is supported they would add little advantages in
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terms of portability.
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@section ffmpeg doesnt contain any debugging symbols ?
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try ffmpeg_g, ffplay_g, ...
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@bye
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