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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 I cannot read this file although this format seems to be supported by ffmpeg.
15 Even if ffmpeg can read the file format, it may not support all its
16 codecs. Please consult the supported codec list in the ffmpeg
17 documentation.
19 @section How do I encode JPEGs to another format ?
21 If the JPEGs are named img1.jpg, img2.jpg, img3.jpg,..., use:
23 @example
24 ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
25 @end example
27 @samp{%d} is replaced by the image number.
29 @file{img%03d.jpg} generates @file{img001.jpg}, @file{img002.jpg}, etc...
31 The same system is used for the other image formats.
33 @section How do I encode movie to single pictures ?
35 Use:
37 @example
38 ffmpeg -i movie.mpg movie%d.jpg
39 @end example
41 The @file{movie.mpg} used as input will be converted to
42 @file{movie1.jpg}, @file{movie2.jpg}, etc...
44 Instead of relying on file format self-recognition, you may also use
45 @table @option
46 @item -vcodec ppm
47 @item -vcodec png
48 @item -vcodec mjpeg
49 @end table
50 to force the encoding.
52 Applying that to the previous example:
53 @example
54 ffmpeg -i movie.mpg -f image2 -vcodec mjpeg menu%d.jpg
55 @end example
57 Beware that there is no "jpeg" codec. Use "mjpeg" instead.
59 @section FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it ?
61 No. FFmpeg only supports open source codecs. Windows DLLs are not
62 portable, bloated and often slow.
64 @section I get "Unsupported codec (id=86043) for input stream #0.1". What is the problem ?
66 This is the Qcelp codec, FFmpeg has no support for that codec currently. Try mencoder/mplayer it might work.
68 @section Why do I see a slight quality degradation with multithreaded MPEG* encoding ?
70 For multithreaded MPEG* encoding, the encoded slices must be independent,
71 otherwise thread n would practically have to wait for n-1 to finish, so it's
72 quite logical that there is a small reduction of quality. This is not a bug.
74 @section How can I read from the standard input or write to the standard output ?
76 Use @file{-} as filename.
78 @section Why does ffmpeg not decode audio in VOB files ?
80 The audio is AC3 (a.k.a. A/52). AC3 decoding is an optional component in ffmpeg
81 as the component that handles AC3 decoding (liba52) is currently released under
82 the GPL. If you have liba52 installed on your system, enable AC3 decoding
83 with @code{./configure --enable-liba52 --enable-gpl}. Take care: by
84 enabling AC3, you automatically change the license of libavcodec from
85 LGPL to GPL.
87 @section Which codecs are supported by Windows ?
89 Windows does not support standard formats like MPEG very well, unless you
90 install some additional codecs
92 The following list of video codecs should work on most Windows systems:
93 @table @option
94 @item msmpeg4v2
95 .avi/.asf
96 @item msmpeg4
97 .asf only
98 @item wmv1
99 .asf only
100 @item wmv2
101 .asf only
102 @item mpeg4
103 only if you have some MPEG-4 codec installed like ffdshow or XviD
104 @item mpeg1
105 .mpg only
106 @end table
107 Note, ASF files often have .wmv or .wma extensions in Windows. It should also
108 be mentioned that Microsoft claims a patent on the ASF format, and may sue
109 or threaten users who create ASF files with non-Microsoft software. It is
110 strongly advised to avoid ASF where possible.
112 The following list of audio codecs should work on most Windows systems:
113 @table @option
114 @item adpcm_ima_wav
115 @item adpcm_ms
116 @item pcm
117 @item mp3
118 if some MP3 codec like LAME is installed
119 @end table
121 @section Why does the chrominance data seem to be sampled at a different time from the luminance data on bt8x8 captures on Linux?
123 This is a well-known bug in the bt8x8 driver. For 2.4.26 there is a patch at
124 (@url{}). This may also
125 apply cleanly to other 2.4-series kernels.
127 @section How do I avoid the ugly aliasing artifacts in bt8x8 captures on Linux?
129 Pass 'combfilter=1 lumafilter=1' to the bttv driver. Note though that 'combfilter=1'
130 will cause somewhat too strong filtering. A fix is to apply (@url{})
131 or (@url{})
132 and pass 'combfilter=2'.
134 @section I have a problem with an old version of ffmpeg; where should I report it?
135 Nowhere. Upgrade to the latest release or if there is no recent release upgrade
136 to Subversion HEAD. You could also try to report it. Maybe you will get lucky and
137 become the first person in history to get an answer different from "upgrade
138 to Subversion HEAD".
140 @section -f jpeg doesn't work.
142 Try '-f image2 test%d.jpg'.
144 @section Why can I not change the framerate?
146 Some codecs, like MPEG-1/2, only allow a small number of fixed framerates.
147 Choose a different codec with the -vcodec command line option.
149 @section ffmpeg does not work; What is wrong?
151 Try a 'make distclean' in the ffmpeg source directory before the build. If this does not help see
152 (@url{}).
154 @section How do I encode XviD or DivX video with ffmpeg?
156 Both XviD and DivX (version 4+) are implementations of the ISO MPEG-4
157 standard (note that there are many other coding formats that use this
158 same standard). Thus, use '-vcodec mpeg4' to encode these formats. The
159 default fourcc stored in an MPEG-4-coded file will be 'FMP4'. If you want
160 a different fourcc, use the '-vtag' option. E.g., '-vtag xvid' will
161 force the fourcc 'xvid' to be stored as the video fourcc rather than the
162 default.
164 @section How do I encode videos which play on the iPod?
166 @table @option
167 @item needed stuff
168 -acodec aac -vcodec mpeg4 width<=320 height<=240
169 @item working stuff
170 4mv, title
171 @item non-working stuff
172 B-frames
173 @item example command line
174 ffmpeg -i input -acodec aac -ab 128kb -vcodec mpeg4 -b 1200kb -mbd 2 -flags +4mv+trell -aic 2 -cmp 2 -subcmp 2 -s 320x180 -title X output.mp4
175 @end table
177 @section How do I encode videos which play on the PSP?
179 @table @option
180 @item needed stuff
181 -acodec aac -vcodec mpeg4 width*height<=76800 width%16=0 height%16=0 -ar 24000 -r 30000/1001 or 15000/1001 -f psp
182 @item working stuff
183 4mv, title
184 @item non-working stuff
185 B-frames
186 @item example command line
187 ffmpeg -i input -acodec aac -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
188 @item needed stuff for H.264
189 -acodec aac -vcodec h264 width*height<=76800 width%16=0? height%16=0? -ar 48000 -coder 1 -r 30000/1001 or 15000/1001 -f psp
190 @item working stuff for H.264
191 title, loop filter
192 @item non-working stuff for H.264
194 @item example command line
195 ffmpeg -i input -acodec aac -ab 128kb -vcodec h264 -b 1200kb -ar 48000 -mbd 2 -coder 1 -cmp 2 -subcmp 2 -s 368x192 -r 30000/1001 -title X -f psp -flags loop -trellis 2 -partitions parti4x4+parti8x8+partp4x4+partp8x8+partb8x8 output.mp4
196 @end table
198 @section Which are good parameters for encoding high quality MPEG-4?
200 '-mbd rd -flags +4mv+trell+aic -cmp 2 -subcmp 2 -g 300 -pass 1/2',
201 things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd'.
203 @section Which are good parameters for encoding high quality MPEG-1/MPEG-2?
205 '-mbd rd -flags +trell -cmp 2 -subcmp 2 -g 100 -pass 1/2'
206 but beware the '-g 100' might cause problems with some decoders.
207 Things to try: '-bf 2', '-flags qprd', '-flags mv0', '-flags skiprd.
209 @section Interlaced video looks very bad when encoded with ffmpeg, whats wrong?
211 You should use '-flags +ilme+ildct' and maybe '-flags +alt' for interlaced
212 material, and try '-top 0/1' if the result looks really messed-up.
214 @section How can I read DirectShow files?
216 If you have built FFmpeg with @code{./configure --enable-avisynth}
217 (only possible on MinGW/Cygwin platforms),
218 then you may use any file that DirectShow can read as input.
219 (Be aware that this feature has been recently added,
220 so you will need to help yourself in case of problems.)
222 Just create an "input.avs" text file with this single line ...
223 @example
224 DirectShowSource("C:\path to your file\yourfile.asf")
225 @end example
226 ... and then feed that text file to FFmpeg:
227 @example
228 ffmpeg -i input.avs
229 @end example
231 For ANY other help on Avisynth, please visit @url{}.
233 @section My bugreport/mail to ffmpeg-devel/user has not received any replies.
235 Likely reasons
236 @itemize
237 @item We are busy and haven't had time yet to read your report or
238 investigate the issue.
239 @item You didn't follow bugreports.html.
240 @item You didn't use Subversion HEAD.
241 @item You reported a segmentation fault without gdb output.
242 @item You describe a problem but not how to reproduce it.
243 @item It's unclear if you use ffmpeg as command line tool or use
244 libav* from another application.
245 @item You speak about a video having problems on playback but
246 not what you use to play it.
247 @item We have no faint clue what you are talking about besides
248 that it is related to FFmpeg.
249 @end itemize
251 @chapter Development
253 @section When will the next FFmpeg version be released? / Why are FFmpeg releases so few and far between?
255 Like most open source projects FFmpeg suffers from a certain lack of
256 manpower. For this reason the developers have to prioritize the work
257 they do and putting out releases is not at the top of the list, fixing
258 bugs and reviewing patches takes precedence. Please don't complain or
259 request more timely and/or frequent releases unless you are willing to
260 help out creating them.
262 @section Why doesn't FFmpeg support feature [xyz]?
264 Because no one has taken on that task yet. FFmpeg development is
265 driven by the tasks that are important to the individual developers.
266 If there is a feature that is important to you, the best way to get
267 it implemented is to undertake the task yourself.
270 @section Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat ?
272 Yes. Read the Developers Guide of the FFmpeg documentation. Alternatively,
273 examine the source code for one of the many open source projects that
274 already incorporate ffmpeg at (@url{projects.php}).
276 @section Can you support my C compiler XXX ?
278 It depends. If your compiler is C99-compliant, then patches to support
279 it are likely to be welcome if they do not pollute the source code
280 with @code{#ifdef}s related to the compiler.
282 @section Visual C++ produces many errors.
284 Visual C++ is not compliant to the C standard and does not support
285 the inline assembly used in FFmpeg.
286 If you wish - for whatever weird reason - to use Visual C++ for your
287 project then you can link the Visual C++ code with libav* as long as
288 you compile the latter with a working C compiler. For more information, see
289 the @emph{Visual C++ compatibility} section in the FFmpeg documentation.
291 There have been efforts to make FFmpeg compatible with Visual C++ in the
292 past. However, they have all been rejected as too intrusive, especially
293 since MinGW does the job perfectly adequately. None of the core developers
294 work with Visual C++ and thus this item is low priority. Should you find
295 the silver bullet that solves this problem, feel free to shoot it at us.
297 @section Can I use FFmpeg or libavcodec under Windows ?
299 Yes, but the MinGW tools @emph{must} be used to compile FFmpeg. You
300 can link the resulting DLLs with any other Windows program. Read the
301 @emph{Native Windows Compilation} and @emph{Visual C++ compatibility}
302 sections in the FFmpeg documentation to find more information.
304 To get help and instructions for using FFmpeg under Windows, check out
305 the FFmpeg Windows Help Forum at
306 @url{}.
308 @section Can you add automake, libtool or autoconf support ?
310 No. These tools are too bloated and they complicate the build.
312 @section Why not rewrite ffmpeg in object-oriented C++ ?
314 ffmpeg is already organized in a highly modular manner and does not need to
315 be rewritten in a formal object language. Further, many of the developers
316 favor straight C; it works for them. For more arguments on this matter,
317 read "Programming Religion" at (@url{}).
319 @section Why are the ffmpeg programs devoid of debugging symbols ?
321 The build process creates ffmpeg_g, ffplay_g, etc. which contain full debug
322 information. Those binaries are strip'd to create ffmpeg, ffplay, etc. If
323 you need the debug information, used the *_g versions.
325 @section I do not like the LGPL, can I contribute code under the GPL instead ?
327 Yes, as long as the code is optional and can easily and cleanly be placed
328 under #ifdef CONFIG_GPL without breaking anything. So for example a new codec
329 or filter would be OK under GPL while a bugfix to LGPL code would not.
331 @section I want to compile xyz.c alone but my compiler produced many errors.
333 Common code is in its own files in libav* and is used by the individual
334 codecs. They will not work without the common parts, you have to compile
335 the whole libav*. If you wish, disable some parts with configure switches.
336 You can also try to hack it and remove more, but if you had problems fixing
337 the compilation failure then you are probably not qualified for this.
339 @section I have a file in memory / a API different from *open/*read/ libc how do i use it with libavformat ?
341 You have to implement a URLProtocol, see libavformat/file.c in FFmpeg
342 and libmpdemux/demux_lavf.c in MPlayer sources.
344 @section I get "No compatible shell script interpreter found." in MSys.
346 The standard MSys bash (2.04) is broken. You need to install 2.05 or later.
348 @section I tried to pass RTP packets into a decoder, but it doesn't work.
350 Of course not, you MUST strip ALL RTP headers and assemble valid packets
351 first, an MP3 decoder decodes MP3 packets not bastardized MP3 packets
352 encapsulated in RTP. The same applies to all decoders, this is not specific
353 to ffmpeg or libavcodec.
355 @bye