mirror of https://git.ffmpeg.org/ffmpeg.git
186 lines
6.6 KiB
Plaintext
186 lines
6.6 KiB
Plaintext
\input texinfo @c -*- texinfo -*-
|
|
|
|
@settitle FFmpeg FAQ
|
|
@titlepage
|
|
@sp 7
|
|
@center @titlefont{FFmpeg FAQ}
|
|
@sp 3
|
|
@end titlepage
|
|
|
|
|
|
@chapter General Problems
|
|
|
|
@section ffserver does 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. If you have time and experience, please help us fix it.
|
|
|
|
@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 synchronization problems when grabbing.
|
|
|
|
Currently, the grabbing stuff does not handle synchronisation
|
|
correctly. You are free to correct it. A fix is planned.
|
|
|
|
@section How do I encode JPEGs to another format ?
|
|
|
|
If the JPEGs are named img1.jpg, img2.jpg, img3.jpg,..., use:
|
|
|
|
@example
|
|
ffmpeg -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 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 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://www.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://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 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 CVS. 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 CVS".
|
|
|
|
@section -f jpeg doesn't work.
|
|
|
|
Try '-f image -img jpeg 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{ffmpeg-bugreport.html}).
|
|
|
|
@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.
|
|
|
|
@chapter Development
|
|
|
|
@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} section 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.
|
|
|
|
@bye
|