* adding Michael's explanation to the FAQ
[libav.git] / doc / faq.texi
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1\input texinfo @c -*- texinfo -*-
2
3@settitle FFmpeg FAQ
4@titlepage
5@sp 7
6@center @titlefont{FFmpeg FAQ}
7@sp 3
8@end titlepage
9
10
11@chapter General Problems
12
13@section ffserver doesn't not work.
14
15ffmpeg development is now concentrated on the codec and format
16handling. New developments broke ffserver, so don't expect it to work
f2fe8752 17correctly. If you have time and experience, please help us fix it.
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18
19@section I cannot read this file although this format seems to be suppored by ffmpeg.
20
21Even if ffmpeg can read the file format, it may not support all its
22codecs. Please consult the supported codec list in the ffmpeg
23documentation.
24
25@section I get audio/video synchro problems when grabbing.
26
27Currently, the grabbing stuff does not handle synchronisation
28correctly. You are free to correct it. It is planned to fix it ASAP.
29
30@section How do I encode jpegs to another format ?
31
32If the jpegs are named img1.jpg, img2.jpg, img3.jpg,..., use:
33
34@example
35 ffmpeg -i img%d.jpg /tmp/a.mpg
36@end example
37
38@samp{%d} is replaced by the image number.
39
40@file{img%03d.jpg} generates @file{img001.jpg}, @file{img002.jpg}, etc...
41
42The same system is used for the other image formats.
43
44@section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it ?
45
46No. FFmpeg only supports open source codecs. Windows DLLs are not
47portable, bloated and often slow.
48
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49@section Why do I see a slight quality degradation with multithreaded MPEG* encoding ?
50
51For multithreaded MPEG* encoding, the encoded slices must be independent,
52otherwise thread n would practically have to wait for n-1 to finish, so its
53quite logic that there is a small reduction of quality, this is not a bug
54
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55@section How can I read from the standard input or write to the standard output ?
56
57Use @file{-} as filename.
58
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59@section Why Audio is not decoded in VOB files ?
60
61AC3 decoding is optional as the codec is currently released under the
62GPL. Enable it with @code{./configure --enable-a52}. Take care: by
63enabling AC3, you automatically change the license of libavcodec from
64LGPL to GPL.
65
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66@section Which codecs are supported by windows ?
67
68Windows does not support standard formats like mpeg very well, unless you
69install some additional codecs
70
71The following list of video codecs should work on most windows systems
72@table @option
73@item msmpeg4v2
74.avi/.asf
75@item msmpeg4
76.asf only
77@item wmv1
78.asf only
79@item wmv2
80.asf only
81@item mpeg4
82only if you have some mpeg4 codec installed like ffdshow or xvid
83@item mpeg1
84.mpg only
85@end table
86note, asf often uses .wmv or .wma extensions in windows, it should also be
87mentioned that asf is patented, so microsoft may sue or threaten users who
88use it if they see any reason to do so, it is strongly recommanded to avoid asf
89for any use
90
91The following list of audio codecs should work on most windows systems
92@table @option
93@item adpcm_ima_wav
94@item adpcm_ms
95@item pcm
96@item mp3
97if some mp3 codec like lame is installed
98@end table
99
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100@section The chrominance seems to come from a different time then the luminance on bt8x8 captures on linux?
101
102well known bug in the bt8x8 driver, for 2.4.26 theres a patch at
103(@url{http://www.mplayerhq.hu/~michael/bttv-420-2.4.26.patch}), i suspect that
104this will also apply cleanly to other 2.4 kernels
105
106@section How to avoid the ugly aliassing artefacts in bt8x8 captures on linux?
107
108pass 'combfilter=1 lumafilter=1' to the bttv driver, note though that 'combfilter=1'
109will cause somewhat too strong filtering, a fix is too apply (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.4.26.patch})
fc3e9202 110or (@url{http://www.mplayerhq.hu/~michael/bttv-comb-2.6.6.patch})
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111and pass 'combfilter=2'
112
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113@section I have a problem with an old version of ffmpeg, where should i report it?
114Nowhere, upgrade to the latest release or if there is no recent release upgrade
115to cvs, you could also try to report it, maybe you are lucky and
116will become the first person in history to get a different awnser from "upgrade
117to cvs".
118
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119@section -f jpeg doesnt work.
120
121try '-f image -img jpeg test%d.jpg'
122
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123@chapter Development
124
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125@section Are there examples of use of the FFmpeg libraries libavcodec and libavformat ?
126
127Yes. Read the Developers Guide of the FFmpeg documentation.
128
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129@section Can you support my C compiler XXX ?
130
131No. Only GCC is supported. GCC is ported on most systems available and I
132don't see the need to pollute the source code with @code{#ifdef}s
133related to the compiler.
134
988a9f9e 135@section Can I use FFmpeg or libavcodec under Windows ?
7ff56c72 136
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137Yes, but the MinGW tools @emph{must} be used to compile FFmpeg. You
138can link the resulting DLLs with any other Windows program. Read the
139@emph{Native Windows Compilation} section in the FFmpeg documentation
140to have more information.
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141
142@section Can you add automake, libtool or autoconf support ?
143
144No. These tools are too blowted and they complicate the build. Moreover,
145since only @samp{gcc} is supported they would add little advantages in
146terms of portability.
147
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148@section ffmpeg doesnt contain any debugging symbols ?
149
150try ffmpeg_g, ffplay_g, ...
151
7ff56c72 152@bye