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   8 <H1>FFmpeg Documentation</H1>
   9 <P>
  10 <P><HR><P>
  11 <H1>Table of Contents</H1>
  12 <UL>
  13 <LI><A NAME="TOC1" HREF="ffmpeg-doc.html#SEC1">1. Introduction</A>
  14 <LI><A NAME="TOC2" HREF="ffmpeg-doc.html#SEC2">2. Quick Start</A>
  15 <UL>
  16 <LI><A NAME="TOC3" HREF="ffmpeg-doc.html#SEC3">2.1 Video and Audio grabbing</A>
  17 <LI><A NAME="TOC4" HREF="ffmpeg-doc.html#SEC4">2.2 Video and Audio file format convertion</A>
  18 </UL>
  19 <LI><A NAME="TOC5" HREF="ffmpeg-doc.html#SEC5">3. Invocation</A>
  20 <UL>
  21 <LI><A NAME="TOC6" HREF="ffmpeg-doc.html#SEC6">3.1 Syntax</A>
  22 <LI><A NAME="TOC7" HREF="ffmpeg-doc.html#SEC7">3.2 Main options</A>
  23 <LI><A NAME="TOC8" HREF="ffmpeg-doc.html#SEC8">3.3 Video Options</A>
  24 <LI><A NAME="TOC9" HREF="ffmpeg-doc.html#SEC9">3.4 Audio Options</A>
  25 <LI><A NAME="TOC10" HREF="ffmpeg-doc.html#SEC10">3.5 Advanced options</A>
  26 <LI><A NAME="TOC11" HREF="ffmpeg-doc.html#SEC11">3.6 Protocols</A>
  27 </UL>
  28 <LI><A NAME="TOC12" HREF="ffmpeg-doc.html#SEC12">4. Tips</A>
  29 <LI><A NAME="TOC13" HREF="ffmpeg-doc.html#SEC13">5. Supported File Formats and Codecs</A>
  30 <UL>
  31 <LI><A NAME="TOC14" HREF="ffmpeg-doc.html#SEC14">5.1 File Formats</A>
  32 <LI><A NAME="TOC15" HREF="ffmpeg-doc.html#SEC15">5.2 Video Codecs</A>
  33 <LI><A NAME="TOC16" HREF="ffmpeg-doc.html#SEC16">5.3 Audio Codecs</A>
  34 </UL>
  35 <LI><A NAME="TOC17" HREF="ffmpeg-doc.html#SEC17">6. Developpers Guide</A>
  36 <UL>
  37 <LI><A NAME="TOC18" HREF="ffmpeg-doc.html#SEC18">6.1 API</A>
  38 <LI><A NAME="TOC19" HREF="ffmpeg-doc.html#SEC19">6.2 Integrating libavcodec or libavformat in your program</A>
  39 <LI><A NAME="TOC20" HREF="ffmpeg-doc.html#SEC20">6.3 Coding Rules</A>
  40 <LI><A NAME="TOC21" HREF="ffmpeg-doc.html#SEC21">6.4 Submitting patches</A>
  41 <LI><A NAME="TOC22" HREF="ffmpeg-doc.html#SEC22">6.5 Regression tests</A>
  42 </UL>
  43 </UL>
  44 <P><HR><P>
  45
  46 <P>
  47 FFmpeg Documentation
  48
  49
  50
  51
  52 <H1><A NAME="SEC1" HREF="ffmpeg-doc.html#TOC1">1. Introduction</A></H1>
  53
  54 <P>
  55 FFmpeg is a very fast video and audio converter. It can also grab from
  56 a live audio/video source.
  57
  58 The command line interface is designed to be intuitive, in the sense
  59 that ffmpeg tries to figure out all the parameters, when
  60 possible. You have usually to give only the target bitrate you want.
  61
  62
  63 <P>
  64 FFmpeg can also convert from any sample rate to any other, and resize
  65 video on the fly with a high quality polyphase filter.
  66
  67
  68
  69
  70 <H1><A NAME="SEC2" HREF="ffmpeg-doc.html#TOC2">2. Quick Start</A></H1>
  71
  72
  73
  74 <H2><A NAME="SEC3" HREF="ffmpeg-doc.html#TOC3">2.1 Video and Audio grabbing</A></H2>
  75
  76 <P>
  77  FFmpeg can use a video4linux compatible video source and any Open Sound
  78   System audio source:
  79
  80 <PRE>
  81   ffmpeg /tmp/out.mpg
  82 </PRE>
  83
  84 <P>
  85   Note that you must activate the right video source and channel
  86   before launching ffmpeg. You can use any TV viewer such as xawtv by
  87   Gerd Knorr which I find very good. You must also set correctly the
  88   audio recording levels with a standard mixer.
  89
  90
  91
  92
  93 <H2><A NAME="SEC4" HREF="ffmpeg-doc.html#TOC4">2.2 Video and Audio file format convertion</A></H2>
  94
  95 <P>
  96 * ffmpeg can use any supported file format and protocol as input:
  97
  98
  99 <P>
 100 Examples:
 101
 102
 103 <P>
 104 * You can input from YUV files:
 105
 106
 107
 108 <PRE>
 109   ffmpeg -i /tmp/test%d.Y /tmp/out.mpg
 110 </PRE>
 111
 112 <P>
 113   It will use the files:
 114
 115 <PRE>
 116        /tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
 117        /tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
 118 </PRE>
 119
 120 <P>
 121   The Y files use twice the resolution of the U and V files. They are
 122   raw files, without header. They can be generated by all decent video
 123   decoders. You must specify the size of the image with the '-s' option
 124   if ffmpeg cannot guess it.
 125
 126
 127 <P>
 128 * You can input from a RAW YUV420P file:
 129
 130
 131
 132 <PRE>
 133   ffmpeg -i /tmp/test.yuv /tmp/out.avi
 134 </PRE>
 135
 136 <P>
 137   The RAW YUV420P is a file containing RAW YUV planar, for each frame first
 138   come the Y plane followed by U and V planes, which are half vertical and
 139   horizontal resolution.
 140
 141
 142 <P>
 143 * You can output to a RAW YUV420P file:
 144
 145
 146
 147 <PRE>
 148   ffmpeg -i mydivx.avi -o hugefile.yuv
 149 </PRE>
 150
 151 <P>
 152 * You can set several input files and output files:
 153
 154
 155
 156 <PRE>
 157   ffmpeg -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
 158 </PRE>
 159
 160 <P>
 161   Convert the audio file a.wav and the raw yuv video file a.yuv
 162   to mpeg file a.mpg
 163
 164
 165 <P>
 166 * You can also do audio and video convertions at the same time:
 167
 168
 169
 170 <PRE>
 171   ffmpeg -i /tmp/a.wav -ar 22050 /tmp/a.mp2
 172 </PRE>
 173
 174 <P>
 175   Convert the sample rate of a.wav to 22050 Hz and encode it to MPEG audio.
 176
 177
 178 <P>
 179 * You can encode to several formats at the same time and define a
 180   mapping from input stream to output streams:
 181
 182
 183
 184 <PRE>
 185   ffmpeg -i /tmp/a.wav -ab 64 /tmp/a.mp2 -ab 128 /tmp/b.mp2 -map 0:0 -map 0:0
 186 </PRE>
 187
 188 <P>
 189   Convert a.wav to a.mp2 at 64 kbits and b.mp2 at 128 kbits. '-map
 190   file:index' specify which input stream is used for each output
 191   stream, in the order of the definition of output streams.
 192
 193
 194 <P>
 195 * You can transcode decrypted VOBs
 196
 197
 198
 199 <PRE>
 200   ffmpeg -i snatch_1.vob -f avi -vcodec mpeg4 -b 800 -g 300 -bf 2 -acodec mp3 -ab 128 snatch.avi
 201 </PRE>
 202
 203 <P>
 204   This is a typicall DVD ripper example, input from a VOB file, output
 205   to an AVI file with MPEG-4 video and MP3 audio, note that in this
 206   command we use B frames so the MPEG-4 stream is DivX5 compatible, GOP
 207   size is 300 that means an INTRA frame every 10 seconds for 29.97 fps
 208   input video.  Also the audio stream is MP3 encoded so you need LAME
 209   support which is enabled using <CODE>--enable-mp3lame</CODE> when
 210   configuring.  The mapping is particullary usefull for DVD transcoding
 211   to get the desired audio language.
 212
 213
 214 <P>
 215   NOTE: to see the supported input formats, use <CODE>ffmpeg -formats</CODE>.
 216
 217
 218
 219
 220 <H1><A NAME="SEC5" HREF="ffmpeg-doc.html#TOC5">3. Invocation</A></H1>
 221
 222
 223
 224 <H2><A NAME="SEC6" HREF="ffmpeg-doc.html#TOC6">3.1 Syntax</A></H2>
 225
 226 <P>
 227  The generic syntax is:
 228
 229
 230
 231 <PRE>
 232   ffmpeg [[options][-i input_file]]... {[options] output_file}...
 233 </PRE>
 234
 235 <P>
 236   If no input file is given, audio/video grabbing is done.
 237
 238
 239 <P>
 240   As a general rule, options are applied to the next specified
 241   file. For example, if you give the '-b 64' option, it sets the video
 242   bitrate of the next file. Format option may be needed for raw input
 243   files.
 244
 245
 246 <P>
 247   By default, ffmpeg tries to convert as losslessly as possible: it
 248   uses the same audio and video parameter fors the outputs as the one
 249   specified for the inputs.
 250
 251
 252
 253
 254 <H2><A NAME="SEC7" HREF="ffmpeg-doc.html#TOC7">3.2 Main options</A></H2>
 255
 256 <DL COMPACT>
 257
 258 <DT><SAMP>`-L'</SAMP>
 259 <DD>
 260 show license
 261 <DT><SAMP>`-h'</SAMP>
 262 <DD>
 263                   show help
 264 <DT><SAMP>`-formats'</SAMP>
 265 <DD>
 266 show available formats, codecs, protocols, ...
 267 <DT><SAMP>`-f fmt'</SAMP>
 268 <DD>
 269 force format
 270 <DT><SAMP>`-i filename'</SAMP>
 271 <DD>
 272 input file name
 273
 274 <DT><SAMP>`-y'</SAMP>
 275 <DD>
 276 overwrite output files
 277
 278 <DT><SAMP>`-t duration'</SAMP>
 279 <DD>
 280 set the recording time in seconds. <CODE>hh:mm:ss[.xxx]</CODE> syntax is also
 281 supported.
 282
 283 <DT><SAMP>`-title string'</SAMP>
 284 <DD>
 285 set the title
 286
 287 <DT><SAMP>`-author string'</SAMP>
 288 <DD>
 289 set the author
 290
 291 <DT><SAMP>`-copyright string'</SAMP>
 292 <DD>
 293 set the copyright
 294
 295 <DT><SAMP>`-comment string'</SAMP>
 296 <DD>
 297 set the comment
 298
 299 <DT><SAMP>`-b bitrate'</SAMP>
 300 <DD>
 301 set video bitrate (in kbit/s)
 302 </DL>
 303
 304
 305
 306 <H2><A NAME="SEC8" HREF="ffmpeg-doc.html#TOC8">3.3 Video Options</A></H2>
 307
 308 <DL COMPACT>
 309
 310 <DT><SAMP>`-s size'</SAMP>
 311 <DD>
 312 set frame size                       [160x128]
 313 <DT><SAMP>`-r fps'</SAMP>
 314 <DD>
 315 set frame rate                       [25]
 316 <DT><SAMP>`-b bitrate'</SAMP>
 317 <DD>
 318 set the video bitrate in kbit/s      [200]
 319 <DT><SAMP>`-vn'</SAMP>
 320 <DD>
 321 disable video recording              [no]
 322 <DT><SAMP>`-bt tolerance'</SAMP>
 323 <DD>
 324 set video bitrate tolerance (in kbit/s)
 325 <DT><SAMP>`-sameq'</SAMP>
 326 <DD>
 327 use same video quality as source (implies VBR)
 328
 329 <DT><SAMP>`-pass n'</SAMP>
 330 <DD>
 331 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.
 332
 333 <DT><SAMP>`-passlogfile file'</SAMP>
 334 <DD>
 335 select two pass log file name
 336
 337 </DL>
 338
 339
 340
 341 <H2><A NAME="SEC9" HREF="ffmpeg-doc.html#TOC9">3.4 Audio Options</A></H2>
 342
 343 <DL COMPACT>
 344
 345 <DT><SAMP>`-ab bitrate'</SAMP>
 346 <DD>
 347 set audio bitrate (in kbit/s)
 348 <DT><SAMP>`-ar freq'</SAMP>
 349 <DD>
 350  set the audio sampling freq          [44100]
 351 <DT><SAMP>`-ab bitrate'</SAMP>
 352 <DD>
 353  set the audio bitrate in kbit/s      [64]
 354 <DT><SAMP>`-ac channels'</SAMP>
 355 <DD>
 356  set the number of audio channels     [1]
 357 <DT><SAMP>`-an'</SAMP>
 358 <DD>
 359  disable audio recording              [no]
 360 </DL>
 361
 362
 363
 364 <H2><A NAME="SEC10" HREF="ffmpeg-doc.html#TOC10">3.5 Advanced options</A></H2>
 365
 366 <DL COMPACT>
 367
 368 <DT><SAMP>`-map file:stream'</SAMP>
 369 <DD>
 370 set input stream mapping
 371 <DT><SAMP>`-g gop_size'</SAMP>
 372 <DD>
 373 set the group of picture size
 374 <DT><SAMP>`-intra'</SAMP>
 375 <DD>
 376 use only intra frames
 377 <DT><SAMP>`-qscale q'</SAMP>
 378 <DD>
 379 use fixed video quantiser scale (VBR)
 380 <DT><SAMP>`-qmin q'</SAMP>
 381 <DD>
 382 min video quantiser scale (VBR)
 383 <DT><SAMP>`-qmax q'</SAMP>
 384 <DD>
 385 max video quantiser scale (VBR)
 386 <DT><SAMP>`-qdiff q'</SAMP>
 387 <DD>
 388 max difference between the quantiser scale (VBR)
 389 <DT><SAMP>`-qblur blur'</SAMP>
 390 <DD>
 391 video quantiser scale blur (VBR)
 392 <DT><SAMP>`-qcomp compression'</SAMP>
 393 <DD>
 394 video quantiser scale compression (VBR)
 395 <DT><SAMP>`-vd device'</SAMP>
 396 <DD>
 397 set video device
 398 <DT><SAMP>`-vcodec codec'</SAMP>
 399 <DD>
 400 force video codec
 401 <DT><SAMP>`-me method'</SAMP>
 402 <DD>
 403 set motion estimation method
 404 <DT><SAMP>`-bf frames'</SAMP>
 405 <DD>
 406 use 'frames' B frames (only MPEG-4)
 407 <DT><SAMP>`-hq'</SAMP>
 408 <DD>
 409 activate high quality settings
 410 <DT><SAMP>`-4mv'</SAMP>
 411 <DD>
 412 use four motion vector by macroblock (only MPEG-4)
 413 <DT><SAMP>`-ad device'</SAMP>
 414 <DD>
 415 set audio device
 416 <DT><SAMP>`-acodec codec'</SAMP>
 417 <DD>
 418 force audio codec
 419 <DT><SAMP>`-deinterlace'</SAMP>
 420 <DD>
 421 deinterlace pictures
 422 <DT><SAMP>`-benchmark'</SAMP>
 423 <DD>
 424 add timings for benchmarking
 425 <DT><SAMP>`-hex'</SAMP>
 426 <DD>
 427 dump each input packet
 428 <DT><SAMP>`-psnr'</SAMP>
 429 <DD>
 430 calculate PSNR of compressed frames
 431 <DT><SAMP>`-vstats'</SAMP>
 432 <DD>
 433 dump video coding statistics to file
 434 </DL>
 435
 436
 437
 438 <H2><A NAME="SEC11" HREF="ffmpeg-doc.html#TOC11">3.6 Protocols</A></H2>
 439
 440 <P>
 441 The output file can be "-" to output to a pipe. This is only possible
 442 with mpeg1 and h263 formats.
 443
 444
 445 <P>
 446 ffmpeg handles also many protocols specified with the URL syntax.
 447
 448
 449 <P>
 450  Use 'ffmpeg -formats' to have a list of the supported protocols.
 451
 452
 453 <P>
 454  The protocol <CODE>http:</CODE> is currently used only to communicate with
 455  ffserver (see the ffserver documentation). When ffmpeg will be a
 456  video player it will also be used for streaming :-)
 457
 458
 459
 460
 461 <H1><A NAME="SEC12" HREF="ffmpeg-doc.html#TOC12">4. Tips</A></H1>
 462
 463
 464 <UL>
 465 <LI>For streaming at very low bit rate application, use a low frame rate
 466
 467   and a small gop size. This is especially true for real video where
 468   the Linux player does not seem to be very fast, so it can miss
 469   frames. An example is:
 470
 471
 472 <PRE>
 473   ffmpeg -g 3 -r 3 -t 10 -b 50 -s qcif -f rv10 /tmp/b.rm
 474 </PRE>
 475
 476 <LI>The parameter 'q' which is displayed while encoding is the current
 477
 478   quantizer. The value of 1 indicates that a very good quality could
 479   be achieved. The value of 31 indicates the worst quality. If q=31
 480   too often, it means that the encoder cannot compress enough to meet
 481   your bit rate. You must either increase the bit rate, decrease the
 482   frame rate or decrease the frame size.
 483
 484 <LI>If your computer is not fast enough, you can speed up the
 485
 486   compression at the expense of the compression ratio. You can use
 487   '-me zero' to speed up motion estimation, and '-intra' to disable
 488   completly motion estimation (you have only I frames, which means it
 489   is about as good as JPEG compression).
 490
 491 <LI>To have very low bitrates in audio, reduce the sampling frequency
 492
 493   (down to 22050 kHz for mpeg audio, 22050 or 11025 for ac3).
 494
 495 <LI>To have a constant quality (but a variable bitrate), use the option
 496
 497   '-qscale n' when 'n' is between 1 (excellent quality) and 31 (worst
 498   quality).
 499
 500 <LI>When converting video files, you can use the '-sameq' option which
 501
 502   uses in the encoder the same quality factor than in the decoder. It
 503   allows to be almost lossless in encoding.
 504
 505 </UL>
 506
 507
 508
 509 <H1><A NAME="SEC13" HREF="ffmpeg-doc.html#TOC13">5. Supported File Formats and Codecs</A></H1>
 510
 511 <P>
 512 You can use the <CODE>-formats</CODE> option to have an exhaustive list.
 513
 514
 515
 516
 517 <H2><A NAME="SEC14" HREF="ffmpeg-doc.html#TOC14">5.1 File Formats</A></H2>
 518
 519 <P>
 520 FFmpeg supports the following file formats thru the <CODE>libavformat</CODE>
 521 library.
 522
 523
 524 <TABLE BORDER>
 525
 526 <TR><TD>Supported File Format </TD><TD> Encoding </TD><TD> Decoding </TD><TD> Comments</TD>
 527
 528 </TR>
 529 <TR><TD>MPEG audio </TD><TD> X </TD><TD> X</TD>
 530
 531 </TR>
 532 <TR><TD>MPEG1 systems </TD><TD> X  </TD><TD>  X</TD>
 533
 534 </TD><TD> muxed audio and video
 535 </TR>
 536 <TR><TD>MPEG2 PS </TD><TD> X  </TD><TD>  X</TD>
 537
 538 </TD><TD> also known as <CODE>VOB</CODE> file
 539 </TR>
 540 <TR><TD>MPEG2 TS </TD><TD>    </TD><TD>  X</TD>
 541
 542 </TD><TD> also known as DVB Transport Stream
 543 </TR>
 544 <TR><TD>ASF</TD><TD> X </TD><TD> X</TD>
 545
 546 </TR>
 547 <TR><TD>AVI</TD><TD> X </TD><TD> X</TD>
 548
 549 </TR>
 550 <TR><TD>WAV</TD><TD> X </TD><TD> X</TD>
 551
 552 </TR>
 553 <TR><TD>Macromedia Flash</TD><TD> X </TD><TD> X</TD>
 554
 555 </TD><TD> Only embedded audio is decoded
 556 </TR>
 557 <TR><TD>Real Audio and Video </TD><TD> X </TD><TD> X</TD>
 558
 559 </TR>
 560 <TR><TD>PGM, YUV, PPM, JPEG images </TD><TD> X </TD><TD> X</TD>
 561
 562 </TR>
 563 <TR><TD>Animated GIF </TD><TD> X </TD><TD></TD>
 564
 565 </TD><TD> Only uncompressed GIFs are generated
 566 </TR>
 567 <TR><TD>Raw AC3 </TD><TD> X  </TD><TD>  X</TD>
 568
 569 </TR>
 570 <TR><TD>Raw MJPEG </TD><TD> X  </TD><TD>  X</TD>
 571
 572 </TR>
 573 <TR><TD>Raw MPEG video </TD><TD> X  </TD><TD>  X</TD>
 574
 575 </TR>
 576 <TR><TD>Raw PCM8/16 bits, mulaw/Alaw</TD><TD> X  </TD><TD>  X</TD>
 577
 578 </TR>
 579 <TR><TD>SUN AU format </TD><TD> X  </TD><TD>  X</TD>
 580
 581 </TR>
 582 <TR><TD>Quicktime        </TD><TD>   </TD><TD>  X</TD>
 583
 584 </TR>
 585 <TR><TD>MPEG4            </TD><TD>  </TD><TD>  X</TD>
 586
 587 </TD><TD> MPEG4 is a variant of Quicktime
 588 </TR>
 589 <TR><TD>Raw MPEG4 video  </TD><TD>  </TD><TD>  X</TD>
 590
 591 </TD><TD> Only small files are supported.
 592 </TR>
 593 <TR><TD>DV               </TD><TD>  </TD><TD> X</TD>
 594
 595 </TD><TD> Only the video track is decoded.
 596 </TR></TABLE>
 597
 598 <P>
 599 <CODE>X</CODE> means that the encoding (resp. decoding) is supported.
 600
 601
 602
 603
 604 <H2><A NAME="SEC15" HREF="ffmpeg-doc.html#TOC15">5.2 Video Codecs</A></H2>
 605
 606 <TABLE BORDER>
 607
 608 <TR><TD>Supported Codec </TD><TD> Encoding </TD><TD> Decoding </TD><TD> Comments</TD>
 609
 610 </TR>
 611 <TR><TD>MPEG1 video            </TD><TD>  X  </TD><TD>  X</TD>
 612
 613 </TR>
 614 <TR><TD>MPEG2 video            </TD><TD>     </TD><TD>  X</TD>
 615
 616 </TR>
 617 <TR><TD>MPEG4                  </TD><TD>  X  </TD><TD>  X </TD><TD> Also known as DIVX4/5</TD>
 618
 619 </TR>
 620 <TR><TD>MSMPEG4 V1             </TD><TD>  X  </TD><TD>  X</TD>
 621
 622 </TR>
 623 <TR><TD>MSMPEG4 V2             </TD><TD>  X  </TD><TD>  X</TD>
 624
 625 </TR>
 626 <TR><TD>MSMPEG4 V3             </TD><TD>  X  </TD><TD>  X </TD><TD> Also known as DIVX3</TD>
 627
 628 </TR>
 629 <TR><TD>WMV7                   </TD><TD>  X  </TD><TD>  X</TD>
 630
 631 </TR>
 632 <TR><TD>H263(+)                </TD><TD>  X  </TD><TD>  X </TD><TD> Also known as Real Video 1.0</TD>
 633
 634 </TR>
 635 <TR><TD>MJPEG                  </TD><TD>  X  </TD><TD>  X</TD>
 636
 637 </TR>
 638 <TR><TD>DV                     </TD><TD>     </TD><TD>  X</TD>
 639
 640 </TR></TABLE>
 641
 642 <P>
 643 <CODE>X</CODE> means that the encoding (resp. decoding) is supported.
 644
 645
 646
 647
 648 <H2><A NAME="SEC16" HREF="ffmpeg-doc.html#TOC16">5.3 Audio Codecs</A></H2>
 649
 650 <TABLE BORDER>
 651
 652 <TR><TD>Supported Codec </TD><TD> Encoding </TD><TD> Decoding </TD><TD> Comments</TD>
 653
 654 </TR>
 655 <TR><TD>MPEG audio layer 2     </TD><TD>  IX  </TD><TD>  IX</TD>
 656
 657 </TR>
 658 <TR><TD>MPEG audio layer 1/3   </TD><TD> IX   </TD><TD>  IX</TD>
 659
 660 </TD><TD> MP3 encoding is supported thru the external library LAME
 661 </TR>
 662 <TR><TD>AC3                    </TD><TD>  IX  </TD><TD>  X</TD>
 663
 664 </TD><TD> liba52 is used internally for decoding.
 665 </TR>
 666 <TR><TD>Vorbis                 </TD><TD>  X   </TD><TD></TD>
 667
 668 </TD><TD> encoding is supported thru the external library libvorbis.
 669 </TR></TABLE>
 670
 671 <P>
 672 <CODE>X</CODE> means that the encoding (resp. decoding) is supported.
 673
 674
 675 <P>
 676 <CODE>I</CODE> means that an integer only version is available too (ensures highest
 677 performances on systems without hardware floating point support).
 678
 679
 680
 681
 682 <H1><A NAME="SEC17" HREF="ffmpeg-doc.html#TOC17">6. Developpers Guide</A></H1>
 683
 684
 685
 686 <H2><A NAME="SEC18" HREF="ffmpeg-doc.html#TOC18">6.1 API</A></H2>
 687
 688 <UL>
 689 <LI>libavcodec is the library containing the codecs (both encoding and
 690
 691   decoding). See <TT>`libavcodec/apiexample.c'</TT> to see how to use it.
 692
 693 <LI>libavformat is the library containing the file formats handling (mux and
 694
 695   demux code for several formats). (no example yet, the API is likely to
 696   evolve).
 697 </UL>
 698
 699
 700
 701 <H2><A NAME="SEC19" HREF="ffmpeg-doc.html#TOC19">6.2 Integrating libavcodec or libavformat in your program</A></H2>
 702
 703 <P>
 704 You can integrate all the source code of the libraries to link them
 705 statically to avoid any version problem. All you need is to provide a
 706 'config.mak' and a 'config.h' in the parent directory. See the defines
 707 generated by ./configure to understand what is needed.
 708
 709
 710 <P>
 711 You can use libavcodec or libavformat in your commercial program, but
 712 <EM>any patch you make must be published</EM>. The best way to proceed is
 713 to send your patches to the ffmpeg mailing list.
 714
 715
 716
 717
 718 <H2><A NAME="SEC20" HREF="ffmpeg-doc.html#TOC20">6.3 Coding Rules</A></H2>
 719
 720 <P>
 721 ffmpeg is programmed in ANSI C language. GCC extensions are
 722 tolerated. Indent size is 4. The TAB character should not be used.
 723
 724
 725 <P>
 726 The presentation is the one specified by 'indent -i4 -kr'.
 727
 728
 729 <P>
 730 Main priority in ffmpeg is simplicity and small code size (=less
 731 bugs).
 732
 733
 734 <P>
 735 Comments: for functions visible from other modules, use the JavaDoc
 736 format (see examples in <TT>`libav/utils.c'</TT>) so that a documentation
 737 can be generated automatically.
 738
 739
 740
 741
 742 <H2><A NAME="SEC21" HREF="ffmpeg-doc.html#TOC21">6.4 Submitting patches</A></H2>
 743
 744 <P>
 745 When you submit your patch, try to send a unified diff (diff '-u'
 746 option). I cannot read other diffs :-)
 747
 748
 749 <P>
 750 Run the regression tests before submitting a patch so that you can
 751 verify that there is no big problems.
 752
 753
 754 <P>
 755 Except if your patch is really big and adds an important feature, by
 756 submitting it to me, you accept implicitely to put it under my
 757 copyright. I prefer to do this to avoid potential problems if
 758 licensing of ffmpeg changes.
 759
 760
 761 <P>
 762 Patches should be posted as base64 encoded attachments (or any other
 763 encoding which ensures that the patch wont be trashed during
 764 transmission) to the ffmpeg-devel mailinglist, see
 765 <A HREF="http://lists.sourceforge.net/lists/listinfo/ffmpeg-devel">http://lists.sourceforge.net/lists/listinfo/ffmpeg-devel</A>
 766
 767
 768
 769
 770 <H2><A NAME="SEC22" HREF="ffmpeg-doc.html#TOC22">6.5 Regression tests</A></H2>
 771
 772 <P>
 773 Before submitting a patch (or commiting with CVS), you should at least
 774 test that you did not break anything.
 775
 776
 777 <P>
 778 The regression test build a synthetic video stream and a synthetic
 779 audio stream. Then there are encoded then decoded with all codecs or
 780 formats. The CRC (or MD5) of each generated file is recorded in a
 781 result file. Then a 'diff' is launched with the reference results and
 782 the result file.
 783
 784
 785 <P>
 786 Run 'make test' to test all the codecs.
 787
 788
 789 <P>
 790 Run 'make libavtest' to test all the codecs.
 791
 792
 793 <P>
 794 [Of course, some patches may change the regression tests results. In
 795 this case, the regression tests reference results shall be modified
 796 accordingly].
 797
 798
 799 <P><HR><P>
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