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1 \input texinfo @c -*- texinfo -*-
3 @settitle FFmpeg FAQ
4 @titlepage
5 @sp 7
6 @center @titlefont{FFmpeg FAQ}
7 @sp 3
8 @end titlepage
11 @chapter General Problems
13 @section ffserver does not work.
15 ffmpeg development is now concentrated on the codec and format
16 handling. New developments broke ffserver, so don't expect it to work
17 correctly. If you have time and experience, please help us fix it.
19 @section I cannot read this file although this format seems to be supported by ffmpeg.
21 Even if ffmpeg can read the file format, it may not support all its
22 codecs. Please consult the supported codec list in the ffmpeg
23 documentation.
25 @section I get audio/video synchronization problems when grabbing.
27 Currently, the grabbing stuff does not handle synchronisation
28 correctly. You are free to correct it. A fix is planned.
30 @section How do I encode JPEGs to another format ?
32 If the JPEGs are named img1.jpg, img2.jpg, img3.jpg,..., use:
34 @example
35 ffmpeg -i img%d.jpg /tmp/a.mpg
36 @end example
38 @samp{%d} is replaced by the image number.
40 @file{img%03d.jpg} generates @file{img001.jpg}, @file{img002.jpg}, etc...
42 The same system is used for the other image formats.
44 @section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it ?
46 No. FFmpeg only supports open source codecs. Windows DLLs are not
47 portable, bloated and often slow.
49 @section Why do I see a slight quality degradation with multithreaded MPEG* encoding ?
51 For multithreaded MPEG* encoding, the encoded slices must be independent,
52 otherwise thread n would practically have to wait for n-1 to finish, so it's
53 quite logical that there is a small reduction of quality. This is not a bug.
55 @section How can I read from the standard input or write to the standard output ?
57 Use @file{-} as filename.
59 @section Why does ffmpeg not decode audio in VOB files ?
61 The audio is AC3 (a.k.a. A/52). AC3 decoding is an optional component in ffmpeg
62 as the component that handles AC3 decoding (liba52) is currently released under
63 the GPL. If you have liba52 installed on your system, enable AC3 decoding
64 with @code{./configure --enable-a52}. Take care: by
65 enabling AC3, you automatically change the license of libavcodec from
66 LGPL to GPL.
68 @section Which codecs are supported by Windows ?
70 Windows does not support standard formats like MPEG very well, unless you
71 install some additional codecs
73 The following list of video codecs should work on most Windows systems:
74 @table @option
75 @item msmpeg4v2
76 .avi/.asf
77 @item msmpeg4
78 .asf only
79 @item wmv1
80 .asf only
81 @item wmv2
82 .asf only
83 @item mpeg4
84 only if you have some MPEG-4 codec installed like ffdshow or XviD
85 @item mpeg1
86 .mpg only
87 @end table
88 Note, ASF files often have .wmv or .wma extensions in Windows. It should also
89 be mentioned that Microsoft claims a patent on the ASF format, and may sue
90 or threaten users who create ASF files with non-Microsoft software. It is
91 strongly advised to avoid ASF where possible.
93 The following list of audio codecs should work on most Windows systems:
94 @table @option
95 @item adpcm_ima_wav
96 @item adpcm_ms
97 @item pcm
98 @item mp3
99 if some MP3 codec like LAME is installed
100 @end table
102 @section Why does the chrominance data seem to be sampled at a different time from the luminance data on bt8x8 captures on Linux?
104 This is a well-known bug in the bt8x8 driver. For 2.4.26 there is a patch at
105 (@url{http://www.mplayerhq.hu/~michael/bttv-420-2.4.26.patch}). This may also
106 apply cleanly to other 2.4-series kernels.
108 @section How do I avoid the ugly aliasing artifacts in bt8x8 captures on Linux?
110 Pass 'combfilter=1 lumafilter=1' to the bttv driver. Note though that 'combfilter=1'
111 will cause somewhat too strong filtering. A fix is to apply (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.4.26.patch})
112 or (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.6.6.patch})
113 and pass 'combfilter=2'.
115 @section I have a problem with an old version of ffmpeg; where should I report it?
116 Nowhere. Upgrade to the latest release or if there is no recent release upgrade
117 to CVS. You could also try to report it. Maybe you will get lucky and
118 become the first person in history to get an answer different from "upgrade
119 to CVS".
121 @section -f jpeg doesn't work.
123 Try '-f image -img jpeg test%d.jpg'.
125 @section Why can I not change the framerate?
127 Some codecs, like MPEG-1/2, only allow a small number of fixed framerates.
128 Choose a different codec with the -vcodec command line option.
130 @section ffmpeg does not work; What is wrong?
132 Try a 'make distclean' in the ffmpeg source directory. If this does not help see
133 (@url{ffmpeg-bugreport.html}).
135 @section How do I encode XviD or DivX video with ffmpeg?
137 Both XviD and DivX (version 4+) are implementations of the ISO MPEG-4
138 standard (note that there are many other coding formats that use this
139 same standard). Thus, use '-vcodec mpeg4' to encode these formats. The
140 default fourcc stored in an MPEG-4-coded file will be 'FMP4'. If you want
141 a different fourcc, use the '-vtag' option. E.g., '-vtag xvid' will
142 force the fourcc 'xvid' to be stored as the video fourcc rather than the
143 default.
145 @chapter Development
147 @section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat ?
149 Yes. Read the Developers Guide of the FFmpeg documentation. Alternatively,
150 examine the source code for one of the many open source projects that
151 already incorporate ffmpeg at (@url{projects.php}).
153 @section Can you support my C compiler XXX ?
155 No. Only GCC is supported. GCC is ported to most systems available and there
156 is no need to pollute the source code with @code{#ifdef}s
157 related to the compiler.
159 @section Can I use FFmpeg or libavcodec under Windows ?
161 Yes, but the MinGW tools @emph{must} be used to compile FFmpeg. You
162 can link the resulting DLLs with any other Windows program. Read the
163 @emph{Native Windows Compilation} section in the FFmpeg documentation
164 to find more information.
166 @section Can you add automake, libtool or autoconf support ?
168 No. These tools are too bloated and they complicate the build. Moreover,
169 since only @samp{gcc} is supported they would add little advantages in
170 terms of portability.
172 @section Why not rewrite ffmpeg in object-oriented C++ ?
174 ffmpeg is already organized in a highly modular manner and does not need to
175 be rewritten in a formal object language. Further, many of the developers
176 favor straight C; it works for them. For more arguments on this matter,
177 read "Programming Religion" at (@url{http://lkml.org/faq/lkmlfaq-15.html}).
179 @section Why are the ffmpeg programs devoid of debugging symbols ?
181 The build process creates ffmpeg_g, ffplay_g, etc. which contain full debug
182 information. Those binaries are strip'd to create ffmpeg, ffplay, etc. If
183 you need the debug information, used the *_g versions.
185 @bye