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1 \input texinfo @c -*- texinfo -*-
3 @settitle FFmpeg Documentation
4 @titlepage
5 @sp 7
6 @center @titlefont{FFmpeg Documentation}
7 @sp 3
8 @end titlepage
11 @chapter Introduction
13 FFmpeg is a very fast video and audio converter. It can also grab from
14 a live audio/video source.
16 The command line interface is designed to be intuitive, in the sense
17 that ffmpeg tries to figure out all the parameters, when
18 possible. You have usually to give only the target bitrate you want.
20 FFmpeg can also convert from any sample rate to any other, and resize
21 video on the fly with a high quality polyphase filter.
23 @chapter Quick Start
25 @section Video and Audio grabbing
27 FFmpeg can use a video4linux compatible video source and any Open Sound
28 System audio source:
29 @example
30 ffmpeg /tmp/out.mpg
31 @end example
33 Note that you must activate the right video source and channel
34 before launching ffmpeg. You can use any TV viewer such as xawtv by
35 Gerd Knorr which I find very good. You must also set correctly the
36 audio recording levels with a standard mixer.
38 @section Video and Audio file format convertion
40 * ffmpeg can use any supported file format and protocol as input:
42 Examples:
44 * You can input from YUV files:
46 @example
47 ffmpeg -i /tmp/test%d.Y /tmp/out.mpg
48 @end example
50 It will use the files:
51 @example
52 /tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
53 /tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
54 @end example
56 The Y files use twice the resolution of the U and V files. They are
57 raw files, without header. They can be generated by all decent video
58 decoders. You must specify the size of the image with the '-s' option
59 if ffmpeg cannot guess it.
61 * You can input from a RAW YUV420P file:
63 @example
64 ffmpeg -i /tmp/test.yuv /tmp/out.avi
65 @end example
67 The RAW YUV420P is a file containing RAW YUV planar, for each frame first
68 come the Y plane followed by U and V planes, which are half vertical and
69 horizontal resolution.
71 * You can output to a RAW YUV420P file:
73 @example
74 ffmpeg -i mydivx.avi -o hugefile.yuv
75 @end example
77 * You can set several input files and output files:
79 @example
80 ffmpeg -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
81 @end example
83 Convert the audio file a.wav and the raw yuv video file a.yuv
84 to mpeg file a.mpg
86 * You can also do audio and video convertions at the same time:
88 @example
89 ffmpeg -i /tmp/a.wav -ar 22050 /tmp/a.mp2
90 @end example
92 Convert the sample rate of a.wav to 22050 Hz and encode it to MPEG audio.
94 * You can encode to several formats at the same time and define a
95 mapping from input stream to output streams:
97 @example
98 ffmpeg -i /tmp/a.wav -ab 64 /tmp/a.mp2 -ab 128 /tmp/b.mp2 -map 0:0 -map 0:0
99 @end example
101 Convert a.wav to a.mp2 at 64 kbits and b.mp2 at 128 kbits. '-map
102 file:index' specify which input stream is used for each output
103 stream, in the order of the definition of output streams.
105 * You can transcode decrypted VOBs
107 @example
108 ffmpeg -i snatch_1.vob -f avi -vcodec mpeg4 -b 800 -g 300 -bf 2 -acodec mp3 -ab 128 snatch.avi
109 @end example
111 This is a typicall DVD ripper example, input from a VOB file, output
112 to an AVI file with MPEG-4 video and MP3 audio, note that in this
113 command we use B frames so the MPEG-4 stream is DivX5 compatible, GOP
114 size is 300 that means an INTRA frame every 10 seconds for 29.97 fps
115 input video. Also the audio stream is MP3 encoded so you need LAME
116 support which is enabled using @code{--enable-mp3lame} when
117 configuring. The mapping is particullary usefull for DVD transcoding
118 to get the desired audio language.
120 NOTE: to see the supported input formats, use @code{ffmpeg -formats}.
122 @chapter Invocation
124 @section Syntax
126 The generic syntax is:
128 @example
129 ffmpeg [[options][-i input_file]]... {[options] output_file}...
130 @end example
131 If no input file is given, audio/video grabbing is done.
133 As a general rule, options are applied to the next specified
134 file. For example, if you give the '-b 64' option, it sets the video
135 bitrate of the next file. Format option may be needed for raw input
136 files.
138 By default, ffmpeg tries to convert as losslessly as possible: it
139 uses the same audio and video parameter fors the outputs as the one
140 specified for the inputs.
142 @section Main options
144 @table @samp
145 @item -L
146 show license
147 @item -h
148 show help
149 @item -formats
150 show available formats, codecs, protocols, ...
151 @item -f fmt
152 force format
153 @item -i filename
154 input file name
156 @item -y
157 overwrite output files
159 @item -t duration
160 set the recording time in seconds. @code{hh:mm:ss[.xxx]} syntax is also
161 supported.
163 @item -title string
164 set the title
166 @item -author string
167 set the author
169 @item -copyright string
170 set the copyright
172 @item -comment string
173 set the comment
175 @item -b bitrate
176 set video bitrate (in kbit/s)
177 @end table
179 @section Video Options
181 @table @samp
182 @item -s size
183 set frame size [160x128]
184 @item -r fps
185 set frame rate [25]
186 @item -b bitrate
187 set the video bitrate in kbit/s [200]
188 @item -vn
189 disable video recording [no]
190 @item -bt tolerance
191 set video bitrate tolerance (in kbit/s)
192 @item -sameq
193 use same video quality as source (implies VBR)
195 @item -pass n
196 select the pass number (1 or 2). It is useful to do two pass encoding. The statistics of the video are recorded in the first pass and the video at the exact requested bit rate is generated in the second pass.
198 @item -passlogfile file
199 select two pass log file name
201 @end table
203 @section Audio Options
205 @table @samp
206 @item -ab bitrate
207 set audio bitrate (in kbit/s)
208 @item -ar freq
209 set the audio sampling freq [44100]
210 @item -ab bitrate
211 set the audio bitrate in kbit/s [64]
212 @item -ac channels
213 set the number of audio channels [1]
214 @item -an
215 disable audio recording [no]
216 @end table
218 @section Advanced options
220 @table @samp
221 @item -map file:stream
222 set input stream mapping
223 @item -g gop_size
224 set the group of picture size
225 @item -intra
226 use only intra frames
227 @item -qscale q
228 use fixed video quantiser scale (VBR)
229 @item -qmin q
230 min video quantiser scale (VBR)
231 @item -qmax q
232 max video quantiser scale (VBR)
233 @item -qdiff q
234 max difference between the quantiser scale (VBR)
235 @item -qblur blur
236 video quantiser scale blur (VBR)
237 @item -qcomp compression
238 video quantiser scale compression (VBR)
239 @item -vd device
240 set video device
241 @item -vcodec codec
242 force video codec
243 @item -me method
244 set motion estimation method
245 @item -bf frames
246 use 'frames' B frames (only MPEG-4)
247 @item -hq
248 activate high quality settings
249 @item -4mv
250 use four motion vector by macroblock (only MPEG-4)
251 @item -ad device
252 set audio device
253 @item -acodec codec
254 force audio codec
255 @item -deinterlace
256 deinterlace pictures
257 @item -benchmark
258 add timings for benchmarking
259 @item -hex
260 dump each input packet
261 @item -psnr
262 calculate PSNR of compressed frames
263 @item -vstats
264 dump video coding statistics to file
265 @end table
267 @section Protocols
269 The output file can be "-" to output to a pipe. This is only possible
270 with mpeg1 and h263 formats.
272 ffmpeg handles also many protocols specified with the URL syntax.
274 Use 'ffmpeg -formats' to have a list of the supported protocols.
276 The protocol @code{http:} is currently used only to communicate with
277 ffserver (see the ffserver documentation). When ffmpeg will be a
278 video player it will also be used for streaming :-)
280 @chapter Tips
282 @itemize
283 @item For streaming at very low bit rate application, use a low frame rate
284 and a small gop size. This is especially true for real video where
285 the Linux player does not seem to be very fast, so it can miss
286 frames. An example is:
288 @example
289 ffmpeg -g 3 -r 3 -t 10 -b 50 -s qcif -f rv10 /tmp/b.rm
290 @end example
292 @item The parameter 'q' which is displayed while encoding is the current
293 quantizer. The value of 1 indicates that a very good quality could
294 be achieved. The value of 31 indicates the worst quality. If q=31
295 too often, it means that the encoder cannot compress enough to meet
296 your bit rate. You must either increase the bit rate, decrease the
297 frame rate or decrease the frame size.
299 @item If your computer is not fast enough, you can speed up the
300 compression at the expense of the compression ratio. You can use
301 '-me zero' to speed up motion estimation, and '-intra' to disable
302 completly motion estimation (you have only I frames, which means it
303 is about as good as JPEG compression).
305 @item To have very low bitrates in audio, reduce the sampling frequency
306 (down to 22050 kHz for mpeg audio, 22050 or 11025 for ac3).
308 @item To have a constant quality (but a variable bitrate), use the option
309 '-qscale n' when 'n' is between 1 (excellent quality) and 31 (worst
310 quality).
312 @item When converting video files, you can use the '-sameq' option which
313 uses in the encoder the same quality factor than in the decoder. It
314 allows to be almost lossless in encoding.
316 @end itemize
318 @chapter Supported File Formats and Codecs
320 You can use the @code{-formats} option to have an exhaustive list.
322 @section File Formats
324 FFmpeg supports the following file formats thru the @code{libavformat}
325 library.
327 @multitable @columnfractions .4 .1 .1
328 @item Supported File Format @tab Encoding @tab Decoding @tab Comments
329 @item MPEG audio @tab X @tab X
330 @item MPEG1 systems @tab X @tab X
331 @tab muxed audio and video
332 @item MPEG2 PS @tab X @tab X
333 @tab also known as @code{VOB} file
334 @item MPEG2 TS @tab @tab X
335 @tab also known as DVB Transport Stream
336 @item ASF@tab X @tab X
337 @item AVI@tab X @tab X
338 @item WAV@tab X @tab X
339 @item Macromedia Flash@tab X @tab X
340 @tab Only embedded audio is decoded
341 @item Real Audio and Video @tab X @tab X
342 @item PGM, YUV, PPM, JPEG images @tab X @tab X
343 @item Animated GIF @tab X @tab
344 @tab Only uncompressed GIFs are generated
345 @item Raw AC3 @tab X @tab X
346 @item Raw MJPEG @tab X @tab X
347 @item Raw MPEG video @tab X @tab X
348 @item Raw PCM8/16 bits, mulaw/Alaw@tab X @tab X
349 @item SUN AU format @tab X @tab X
350 @item Quicktime @tab @tab X
351 @item MPEG4 @tab @tab X
352 @tab MPEG4 is a variant of Quicktime
353 @item Raw MPEG4 video @tab @tab X
354 @tab Only small files are supported.
355 @item DV @tab @tab X
356 @tab Only the video track is decoded.
357 @end multitable
359 @code{X} means that the encoding (resp. decoding) is supported.
361 @section Video Codecs
363 @multitable @columnfractions .4 .1 .1 .7
364 @item Supported Codec @tab Encoding @tab Decoding @tab Comments
365 @item MPEG1 video @tab X @tab X
366 @item MPEG2 video @tab @tab X
367 @item MPEG4 @tab X @tab X @tab Also known as DIVX4/5
368 @item MSMPEG4 V1 @tab X @tab X
369 @item MSMPEG4 V2 @tab X @tab X
370 @item MSMPEG4 V3 @tab X @tab X @tab Also known as DIVX3
371 @item WMV7 @tab X @tab X
372 @item H263(+) @tab X @tab X @tab Also known as Real Video 1.0
373 @item MJPEG @tab X @tab X
374 @item DV @tab @tab X
375 @end multitable
377 @code{X} means that the encoding (resp. decoding) is supported.
379 Check at @url{} to
380 get a precise comparison of FFmpeg MPEG4 codec compared to the other
381 solutions.
383 @section Audio Codecs
385 @multitable @columnfractions .4 .1 .1 .1 .7
386 @item Supported Codec @tab Encoding @tab Decoding @tab Comments
387 @item MPEG audio layer 2 @tab IX @tab IX
388 @item MPEG audio layer 1/3 @tab IX @tab IX
389 @tab MP3 encoding is supported thru the external library LAME
390 @item AC3 @tab IX @tab X
391 @tab liba52 is used internally for decoding.
392 @item Vorbis @tab X @tab
393 @tab encoding is supported thru the external library libvorbis.
394 @end multitable
396 @code{X} means that the encoding (resp. decoding) is supported.
398 @code{I} means that an integer only version is available too (ensures highest
399 performances on systems without hardware floating point support).
401 @chapter Developpers Guide
403 @section API
404 @itemize
405 @item libavcodec is the library containing the codecs (both encoding and
406 decoding). See @file{libavcodec/apiexample.c} to see how to use it.
408 @item libavformat is the library containing the file formats handling (mux and
409 demux code for several formats). (no example yet, the API is likely to
410 evolve).
411 @end itemize
413 @section Integrating libavcodec or libavformat in your program
415 You can integrate all the source code of the libraries to link them
416 statically to avoid any version problem. All you need is to provide a
417 'config.mak' and a 'config.h' in the parent directory. See the defines
418 generated by ./configure to understand what is needed.
420 You can use libavcodec or libavformat in your commercial program, but
421 @emph{any patch you make must be published}. The best way to proceed is
422 to send your patches to the ffmpeg mailing list.
424 @section Coding Rules
426 ffmpeg is programmed in ANSI C language. GCC extensions are
427 tolerated. Indent size is 4. The TAB character should not be used.
429 The presentation is the one specified by 'indent -i4 -kr'.
431 Main priority in ffmpeg is simplicity and small code size (=less
432 bugs).
434 Comments: for functions visible from other modules, use the JavaDoc
435 format (see examples in @file{libav/utils.c}) so that a documentation
436 can be generated automatically.
438 @section Submitting patches
440 When you submit your patch, try to send a unified diff (diff '-u'
441 option). I cannot read other diffs :-)
443 Run the regression tests before submitting a patch so that you can
444 verify that there is no big problems.
446 Except if your patch is really big and adds an important feature, by
447 submitting it to me, you accept implicitely to put it under my
448 copyright. I prefer to do this to avoid potential problems if
449 licensing of ffmpeg changes.
451 Patches should be posted as base64 encoded attachments (or any other
452 encoding which ensures that the patch wont be trashed during
453 transmission) to the ffmpeg-devel mailinglist, see
454 @url{}
456 @section Regression tests
458 Before submitting a patch (or commiting with CVS), you should at least
459 test that you did not break anything.
461 The regression test build a synthetic video stream and a synthetic
462 audio stream. Then there are encoded then decoded with all codecs or
463 formats. The CRC (or MD5) of each generated file is recorded in a
464 result file. Then a 'diff' is launched with the reference results and
465 the result file.
467 Run 'make test' to test all the codecs.
469 Run 'make libavtest' to test all the codecs.
471 [Of course, some patches may change the regression tests results. In
472 this case, the regression tests reference results shall be modified
473 accordingly].
475 @bye