3 * Copyright (c) 2000 Fabrice Bellard.
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 #include "allformats.h" // for asf_muxer
27 /* Note: when encoding, the first matching tag is used, so order is
28 important if multiple tags possible for a given codec. */
29 const AVCodecTag codec_bmp_tags[] = {
30 { CODEC_ID_H264, MKTAG('H', '2', '6', '4') },
31 { CODEC_ID_H264, MKTAG('h', '2', '6', '4') },
32 { CODEC_ID_H264, MKTAG('X', '2', '6', '4') },
33 { CODEC_ID_H264, MKTAG('x', '2', '6', '4') },
34 { CODEC_ID_H264, MKTAG('a', 'v', 'c', '1') },
35 { CODEC_ID_H264, MKTAG('V', 'S', 'S', 'H') },
37 { CODEC_ID_H263, MKTAG('H', '2', '6', '3') },
38 { CODEC_ID_H263P, MKTAG('H', '2', '6', '3') },
39 { CODEC_ID_H263I, MKTAG('I', '2', '6', '3') }, /* intel h263 */
40 { CODEC_ID_H261, MKTAG('H', '2', '6', '1') },
42 /* added based on MPlayer */
43 { CODEC_ID_H263P, MKTAG('U', '2', '6', '3') },
44 { CODEC_ID_H263P, MKTAG('v', 'i', 'v', '1') },
46 { CODEC_ID_MPEG4, MKTAG('F', 'M', 'P', '4') },
47 { CODEC_ID_MPEG4, MKTAG('D', 'I', 'V', 'X') },
48 { CODEC_ID_MPEG4, MKTAG('D', 'X', '5', '0') },
49 { CODEC_ID_MPEG4, MKTAG('X', 'V', 'I', 'D') },
50 { CODEC_ID_MPEG4, MKTAG('M', 'P', '4', 'S') },
51 { CODEC_ID_MPEG4, MKTAG('M', '4', 'S', '2') },
52 { CODEC_ID_MPEG4, MKTAG(0x04, 0, 0, 0) }, /* some broken avi use this */
54 /* added based on MPlayer */
55 { CODEC_ID_MPEG4, MKTAG('D', 'I', 'V', '1') },
56 { CODEC_ID_MPEG4, MKTAG('B', 'L', 'Z', '0') },
57 { CODEC_ID_MPEG4, MKTAG('m', 'p', '4', 'v') },
58 { CODEC_ID_MPEG4, MKTAG('U', 'M', 'P', '4') },
59 { CODEC_ID_MPEG4, MKTAG('W', 'V', '1', 'F') },
60 { CODEC_ID_MPEG4, MKTAG('S', 'E', 'D', 'G') },
62 { CODEC_ID_MPEG4, MKTAG('R', 'M', 'P', '4') },
64 { CODEC_ID_MSMPEG4V3, MKTAG('D', 'I', 'V', '3') }, /* default signature when using MSMPEG4 */
65 { CODEC_ID_MSMPEG4V3, MKTAG('M', 'P', '4', '3') },
67 /* added based on MPlayer */
68 { CODEC_ID_MSMPEG4V3, MKTAG('M', 'P', 'G', '3') },
69 { CODEC_ID_MSMPEG4V3, MKTAG('D', 'I', 'V', '5') },
70 { CODEC_ID_MSMPEG4V3, MKTAG('D', 'I', 'V', '6') },
71 { CODEC_ID_MSMPEG4V3, MKTAG('D', 'I', 'V', '4') },
72 { CODEC_ID_MSMPEG4V3, MKTAG('A', 'P', '4', '1') },
73 { CODEC_ID_MSMPEG4V3, MKTAG('C', 'O', 'L', '1') },
74 { CODEC_ID_MSMPEG4V3, MKTAG('C', 'O', 'L', '0') },
76 { CODEC_ID_MSMPEG4V2, MKTAG('M', 'P', '4', '2') },
78 /* added based on MPlayer */
79 { CODEC_ID_MSMPEG4V2, MKTAG('D', 'I', 'V', '2') },
81 { CODEC_ID_MSMPEG4V1, MKTAG('M', 'P', 'G', '4') },
83 { CODEC_ID_WMV1, MKTAG('W', 'M', 'V', '1') },
85 /* added based on MPlayer */
86 { CODEC_ID_WMV2, MKTAG('W', 'M', 'V', '2') },
87 { CODEC_ID_DVVIDEO, MKTAG('d', 'v', 's', 'd') },
88 { CODEC_ID_DVVIDEO, MKTAG('d', 'v', 'h', 'd') },
89 { CODEC_ID_DVVIDEO, MKTAG('d', 'v', 's', 'l') },
90 { CODEC_ID_DVVIDEO, MKTAG('d', 'v', '2', '5') },
91 { CODEC_ID_MPEG1VIDEO, MKTAG('m', 'p', 'g', '1') },
92 { CODEC_ID_MPEG1VIDEO, MKTAG('m', 'p', 'g', '2') },
93 { CODEC_ID_MPEG2VIDEO, MKTAG('m', 'p', 'g', '2') },
94 { CODEC_ID_MPEG2VIDEO, MKTAG('M', 'P', 'E', 'G') },
95 { CODEC_ID_MPEG1VIDEO, MKTAG('P', 'I', 'M', '1') },
96 { CODEC_ID_MPEG1VIDEO, MKTAG('V', 'C', 'R', '2') },
97 { CODEC_ID_MPEG1VIDEO, 0x10000001 },
98 { CODEC_ID_MPEG2VIDEO, 0x10000002 },
99 { CODEC_ID_MPEG2VIDEO, MKTAG('D', 'V', 'R', ' ') },
100 { CODEC_ID_MJPEG, MKTAG('M', 'J', 'P', 'G') },
101 { CODEC_ID_MJPEG, MKTAG('L', 'J', 'P', 'G') },
102 { CODEC_ID_LJPEG, MKTAG('L', 'J', 'P', 'G') },
103 { CODEC_ID_MJPEG, MKTAG('J', 'P', 'G', 'L') }, /* Pegasus lossless JPEG */
104 { CODEC_ID_MJPEG, MKTAG('M', 'J', 'L', 'S') }, /* JPEG-LS custom FOURCC for avi - decoder */
105 { CODEC_ID_JPEGLS, MKTAG('M', 'J', 'L', 'S') }, /* JPEG-LS custom FOURCC for avi - encoder */
106 { CODEC_ID_HUFFYUV, MKTAG('H', 'F', 'Y', 'U') },
107 { CODEC_ID_FFVHUFF, MKTAG('F', 'F', 'V', 'H') },
108 { CODEC_ID_CYUV, MKTAG('C', 'Y', 'U', 'V') },
109 { CODEC_ID_RAWVIDEO, 0 },
110 { CODEC_ID_RAWVIDEO, MKTAG('I', '4', '2', '0') },
111 { CODEC_ID_RAWVIDEO, MKTAG('Y', 'U', 'Y', '2') },
112 { CODEC_ID_RAWVIDEO, MKTAG('Y', '4', '2', '2') },
113 { CODEC_ID_RAWVIDEO, MKTAG('Y', 'V', '1', '2') },
114 { CODEC_ID_RAWVIDEO, MKTAG('U', 'Y', 'V', 'Y') },
115 { CODEC_ID_RAWVIDEO, MKTAG('I', 'Y', 'U', 'V') },
116 { CODEC_ID_RAWVIDEO, MKTAG('Y', '8', '0', '0') },
117 { CODEC_ID_INDEO3, MKTAG('I', 'V', '3', '1') },
118 { CODEC_ID_INDEO3, MKTAG('I', 'V', '3', '2') },
119 { CODEC_ID_VP3, MKTAG('V', 'P', '3', '1') },
120 { CODEC_ID_VP3, MKTAG('V', 'P', '3', '0') },
121 { CODEC_ID_VP5, MKTAG('V', 'P', '5', '0') },
122 { CODEC_ID_VP6, MKTAG('V', 'P', '6', '0') },
123 { CODEC_ID_VP6, MKTAG('V', 'P', '6', '1') },
124 { CODEC_ID_VP6, MKTAG('V', 'P', '6', '2') },
125 { CODEC_ID_ASV1, MKTAG('A', 'S', 'V', '1') },
126 { CODEC_ID_ASV2, MKTAG('A', 'S', 'V', '2') },
127 { CODEC_ID_VCR1, MKTAG('V', 'C', 'R', '1') },
128 { CODEC_ID_FFV1, MKTAG('F', 'F', 'V', '1') },
129 { CODEC_ID_XAN_WC4, MKTAG('X', 'x', 'a', 'n') },
130 { CODEC_ID_MSRLE, MKTAG('m', 'r', 'l', 'e') },
131 { CODEC_ID_MSRLE, MKTAG(0x1, 0x0, 0x0, 0x0) },
132 { CODEC_ID_MSVIDEO1, MKTAG('M', 'S', 'V', 'C') },
133 { CODEC_ID_MSVIDEO1, MKTAG('m', 's', 'v', 'c') },
134 { CODEC_ID_MSVIDEO1, MKTAG('C', 'R', 'A', 'M') },
135 { CODEC_ID_MSVIDEO1, MKTAG('c', 'r', 'a', 'm') },
136 { CODEC_ID_MSVIDEO1, MKTAG('W', 'H', 'A', 'M') },
137 { CODEC_ID_MSVIDEO1, MKTAG('w', 'h', 'a', 'm') },
138 { CODEC_ID_CINEPAK, MKTAG('c', 'v', 'i', 'd') },
139 { CODEC_ID_TRUEMOTION1, MKTAG('D', 'U', 'C', 'K') },
140 { CODEC_ID_MSZH, MKTAG('M', 'S', 'Z', 'H') },
141 { CODEC_ID_ZLIB, MKTAG('Z', 'L', 'I', 'B') },
142 { CODEC_ID_SNOW, MKTAG('S', 'N', 'O', 'W') },
143 { CODEC_ID_4XM, MKTAG('4', 'X', 'M', 'V') },
144 { CODEC_ID_FLV1, MKTAG('F', 'L', 'V', '1') },
145 { CODEC_ID_FLASHSV, MKTAG('F', 'S', 'V', '1') },
146 { CODEC_ID_VP6F, MKTAG('V', 'P', '6', 'F') },
147 { CODEC_ID_SVQ1, MKTAG('s', 'v', 'q', '1') },
148 { CODEC_ID_TSCC, MKTAG('t', 's', 'c', 'c') },
149 { CODEC_ID_ULTI, MKTAG('U', 'L', 'T', 'I') },
150 { CODEC_ID_VIXL, MKTAG('V', 'I', 'X', 'L') },
151 { CODEC_ID_QPEG, MKTAG('Q', 'P', 'E', 'G') },
152 { CODEC_ID_QPEG, MKTAG('Q', '1', '.', '0') },
153 { CODEC_ID_QPEG, MKTAG('Q', '1', '.', '1') },
154 { CODEC_ID_WMV3, MKTAG('W', 'M', 'V', '3') },
155 { CODEC_ID_VC1, MKTAG('W', 'V', 'C', '1') },
156 { CODEC_ID_LOCO, MKTAG('L', 'O', 'C', 'O') },
157 { CODEC_ID_WNV1, MKTAG('W', 'N', 'V', '1') },
158 { CODEC_ID_AASC, MKTAG('A', 'A', 'S', 'C') },
159 { CODEC_ID_INDEO2, MKTAG('R', 'T', '2', '1') },
160 { CODEC_ID_FRAPS, MKTAG('F', 'P', 'S', '1') },
161 { CODEC_ID_THEORA, MKTAG('t', 'h', 'e', 'o') },
162 { CODEC_ID_TRUEMOTION2, MKTAG('T', 'M', '2', '0') },
163 { CODEC_ID_CSCD, MKTAG('C', 'S', 'C', 'D') },
164 { CODEC_ID_ZMBV, MKTAG('Z', 'M', 'B', 'V') },
165 { CODEC_ID_KMVC, MKTAG('K', 'M', 'V', 'C') },
166 { CODEC_ID_CAVS, MKTAG('C', 'A', 'V', 'S') },
167 { CODEC_ID_JPEG2000, MKTAG('M', 'J', '2', 'C') },
168 { CODEC_ID_VMNC, MKTAG('V', 'M', 'n', 'c') },
169 { CODEC_ID_NONE, 0 },
172 const AVCodecTag codec_wav_tags[] = {
173 { CODEC_ID_MP2, 0x50 },
174 { CODEC_ID_MP3, 0x55 },
175 { CODEC_ID_AC3, 0x2000 },
176 { CODEC_ID_DTS, 0x2001 },
177 { CODEC_ID_PCM_S16LE, 0x01 },
178 { CODEC_ID_PCM_U8, 0x01 }, /* must come after s16le in this list */
179 { CODEC_ID_PCM_S24LE, 0x01 },
180 { CODEC_ID_PCM_S32LE, 0x01 },
181 { CODEC_ID_PCM_ALAW, 0x06 },
182 { CODEC_ID_PCM_MULAW, 0x07 },
183 { CODEC_ID_ADPCM_MS, 0x02 },
184 { CODEC_ID_ADPCM_IMA_WAV, 0x11 },
185 { CODEC_ID_ADPCM_YAMAHA, 0x20 },
186 { CODEC_ID_ADPCM_G726, 0x45 },
187 { CODEC_ID_ADPCM_IMA_DK4, 0x61 }, /* rogue format number */
188 { CODEC_ID_ADPCM_IMA_DK3, 0x62 }, /* rogue format number */
189 { CODEC_ID_WMAV1, 0x160 },
190 { CODEC_ID_WMAV2, 0x161 },
191 { CODEC_ID_AAC, 0x706d },
192 { CODEC_ID_AAC, 0xff },
193 { CODEC_ID_VORBIS, ('V'<<8)+'o' }, //HACK/FIXME, does vorbis in WAV/AVI have an (in)official id?
194 { CODEC_ID_SONIC, 0x2048 },
195 { CODEC_ID_SONIC_LS, 0x2048 },
196 { CODEC_ID_ADPCM_CT, 0x200 },
197 { CODEC_ID_ADPCM_SWF, ('S'<<8)+'F' },
198 { CODEC_ID_TRUESPEECH, 0x22 },
199 { CODEC_ID_FLAC, 0xF1AC },
200 { CODEC_ID_IMC, 0x401 },
202 /* FIXME: All of the IDs below are not 16 bit and thus illegal. */
203 // for NuppelVideo (nuv.c)
204 { CODEC_ID_PCM_S16LE, MKTAG('R', 'A', 'W', 'A') },
205 { CODEC_ID_MP3, MKTAG('L', 'A', 'M', 'E') },
206 { CODEC_ID_MP3, MKTAG('M', 'P', '3', ' ') },
210 unsigned int codec_get_tag(const AVCodecTag *tags, int id)
212 while (tags->id != CODEC_ID_NONE) {
220 enum CodecID codec_get_id(const AVCodecTag *tags, unsigned int tag)
222 while (tags->id != CODEC_ID_NONE) {
223 if( toupper((tag >> 0)&0xFF) == toupper((tags->tag >> 0)&0xFF)
224 && toupper((tag >> 8)&0xFF) == toupper((tags->tag >> 8)&0xFF)
225 && toupper((tag >>16)&0xFF) == toupper((tags->tag >>16)&0xFF)
226 && toupper((tag >>24)&0xFF) == toupper((tags->tag >>24)&0xFF))
230 return CODEC_ID_NONE;
233 unsigned int av_codec_get_tag(const AVCodecTag *tags[4], enum CodecID id)
236 for(i=0; tags && tags[i]; i++){
237 int tag= codec_get_tag(tags[i], id);
243 enum CodecID av_codec_get_id(const AVCodecTag *tags[4], unsigned int tag)
246 for(i=0; tags && tags[i]; i++){
247 enum CodecID id= codec_get_id(tags[i], tag);
248 if(id!=CODEC_ID_NONE) return id;
250 return CODEC_ID_NONE;
253 unsigned int codec_get_bmp_tag(int id)
255 return codec_get_tag(codec_bmp_tags, id);
258 unsigned int codec_get_wav_tag(int id)
260 return codec_get_tag(codec_wav_tags, id);
263 enum CodecID codec_get_bmp_id(unsigned int tag)
265 return codec_get_id(codec_bmp_tags, tag);
268 enum CodecID codec_get_wav_id(unsigned int tag)
270 return codec_get_id(codec_wav_tags, tag);
274 offset_t start_tag(ByteIOContext *pb, const char *tag)
278 return url_ftell(pb);
281 void end_tag(ByteIOContext *pb, offset_t start)
286 url_fseek(pb, start - 4, SEEK_SET);
287 put_le32(pb, (uint32_t)(pos - start));
288 url_fseek(pb, pos, SEEK_SET);
291 /* WAVEFORMATEX header */
292 /* returns the size or -1 on error */
293 int put_wav_header(ByteIOContext *pb, AVCodecContext *enc)
295 int bps, blkalign, bytespersec;
298 if(!enc->codec_tag || enc->codec_tag > 0xffff)
301 put_le16(pb, enc->codec_tag);
302 put_le16(pb, enc->channels);
303 put_le32(pb, enc->sample_rate);
304 if (enc->codec_id == CODEC_ID_PCM_U8 ||
305 enc->codec_id == CODEC_ID_PCM_ALAW ||
306 enc->codec_id == CODEC_ID_PCM_MULAW) {
308 } else if (enc->codec_id == CODEC_ID_MP2 || enc->codec_id == CODEC_ID_MP3) {
310 } else if (enc->codec_id == CODEC_ID_ADPCM_IMA_WAV || enc->codec_id == CODEC_ID_ADPCM_MS || enc->codec_id == CODEC_ID_ADPCM_G726 || enc->codec_id == CODEC_ID_ADPCM_YAMAHA) { //
312 } else if (enc->codec_id == CODEC_ID_PCM_S24LE) {
314 } else if (enc->codec_id == CODEC_ID_PCM_S32LE) {
320 if (enc->codec_id == CODEC_ID_MP2 || enc->codec_id == CODEC_ID_MP3) {
321 blkalign = enc->frame_size; //this is wrong, but seems many demuxers dont work if this is set correctly
322 //blkalign = 144 * enc->bit_rate/enc->sample_rate;
323 } else if (enc->codec_id == CODEC_ID_ADPCM_G726) { //
325 } else if (enc->block_align != 0) { /* specified by the codec */
326 blkalign = enc->block_align;
328 blkalign = enc->channels*bps >> 3;
329 if (enc->codec_id == CODEC_ID_PCM_U8 ||
330 enc->codec_id == CODEC_ID_PCM_S24LE ||
331 enc->codec_id == CODEC_ID_PCM_S32LE ||
332 enc->codec_id == CODEC_ID_PCM_S16LE) {
333 bytespersec = enc->sample_rate * blkalign;
335 bytespersec = enc->bit_rate / 8;
337 put_le32(pb, bytespersec); /* bytes per second */
338 put_le16(pb, blkalign); /* block align */
339 put_le16(pb, bps); /* bits per sample */
340 if (enc->codec_id == CODEC_ID_MP3) {
341 put_le16(pb, 12); /* wav_extra_size */
343 put_le16(pb, 1); /* wID */
344 put_le32(pb, 2); /* fdwFlags */
345 put_le16(pb, 1152); /* nBlockSize */
346 put_le16(pb, 1); /* nFramesPerBlock */
347 put_le16(pb, 1393); /* nCodecDelay */
348 } else if (enc->codec_id == CODEC_ID_MP2) {
349 put_le16(pb, 22); /* wav_extra_size */
351 put_le16(pb, 2); /* fwHeadLayer */
352 put_le32(pb, enc->bit_rate); /* dwHeadBitrate */
353 put_le16(pb, enc->channels == 2 ? 1 : 8); /* fwHeadMode */
354 put_le16(pb, 0); /* fwHeadModeExt */
355 put_le16(pb, 1); /* wHeadEmphasis */
356 put_le16(pb, 16); /* fwHeadFlags */
357 put_le32(pb, 0); /* dwPTSLow */
358 put_le32(pb, 0); /* dwPTSHigh */
359 } else if (enc->codec_id == CODEC_ID_ADPCM_IMA_WAV) {
360 put_le16(pb, 2); /* wav_extra_size */
362 put_le16(pb, ((enc->block_align - 4 * enc->channels) / (4 * enc->channels)) * 8 + 1); /* wSamplesPerBlock */
363 } else if(enc->extradata_size){
364 put_le16(pb, enc->extradata_size);
365 put_buffer(pb, enc->extradata, enc->extradata_size);
366 hdrsize += enc->extradata_size;
378 /* BITMAPINFOHEADER header */
379 void put_bmp_header(ByteIOContext *pb, AVCodecContext *enc, const AVCodecTag *tags, int for_asf)
381 put_le32(pb, 40 + enc->extradata_size); /* size */
382 put_le32(pb, enc->width);
383 put_le32(pb, enc->height);
384 put_le16(pb, 1); /* planes */
386 put_le16(pb, enc->bits_per_sample ? enc->bits_per_sample : 24); /* depth */
387 /* compression type */
388 put_le32(pb, enc->codec_tag);
389 put_le32(pb, enc->width * enc->height * 3);
395 put_buffer(pb, enc->extradata, enc->extradata_size);
397 if (enc->extradata_size & 1)
400 #endif //CONFIG_MUXERS
402 #ifdef CONFIG_DEMUXERS
403 /* We could be given one of the three possible structures here:
404 * WAVEFORMAT, PCMWAVEFORMAT or WAVEFORMATEX. Each structure
405 * is an expansion of the previous one with the fields added
406 * at the bottom. PCMWAVEFORMAT adds 'WORD wBitsPerSample' and
407 * WAVEFORMATEX adds 'WORD cbSize' and basically makes itself
408 * an openended structure.
410 void get_wav_header(ByteIOContext *pb, AVCodecContext *codec, int size)
415 codec->codec_type = CODEC_TYPE_AUDIO;
416 codec->codec_tag = id;
417 codec->channels = get_le16(pb);
418 codec->sample_rate = get_le32(pb);
419 codec->bit_rate = get_le32(pb) * 8;
420 codec->block_align = get_le16(pb);
421 if (size == 14) { /* We're dealing with plain vanilla WAVEFORMAT */
422 codec->bits_per_sample = 8;
424 codec->bits_per_sample = get_le16(pb);
425 codec->codec_id = wav_codec_get_id(id, codec->bits_per_sample);
427 if (size > 16) { /* We're obviously dealing with WAVEFORMATEX */
428 codec->extradata_size = get_le16(pb);
429 if (codec->extradata_size > 0) {
430 if (codec->extradata_size > size - 18)
431 codec->extradata_size = size - 18;
432 codec->extradata = av_mallocz(codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);
433 get_buffer(pb, codec->extradata, codec->extradata_size);
435 codec->extradata_size = 0;
437 /* It is possible for the chunk to contain garbage at the end */
438 if (size - codec->extradata_size - 18 > 0)
439 url_fskip(pb, size - codec->extradata_size - 18);
444 int wav_codec_get_id(unsigned int tag, int bps)
447 id = codec_get_id(codec_wav_tags, tag);
450 /* handle specific u8 codec */
451 if (id == CODEC_ID_PCM_S16LE && bps == 8)
452 id = CODEC_ID_PCM_U8;
453 if (id == CODEC_ID_PCM_S16LE && bps == 24)
454 id = CODEC_ID_PCM_S24LE;
455 if (id == CODEC_ID_PCM_S16LE && bps == 32)
456 id = CODEC_ID_PCM_S32LE;
459 #endif // CONFIG_DEMUXERS
461 void ff_parse_specific_params(AVCodecContext *stream, int *au_rate, int *au_ssize, int *au_scale)
465 *au_ssize= stream->block_align;
466 if(stream->frame_size && stream->sample_rate){
467 *au_scale=stream->frame_size;
468 *au_rate= stream->sample_rate;
469 }else if(stream->codec_type == CODEC_TYPE_VIDEO){
470 *au_scale= stream->time_base.num;
471 *au_rate = stream->time_base.den;
473 *au_scale= stream->block_align ? stream->block_align*8 : 8;
474 *au_rate = stream->bit_rate;
476 gcd= ff_gcd(*au_scale, *au_rate);