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  1. /*
  2.  * MPEG Audio parser
  3.  * Copyright (c) 2003 Fabrice Bellard
  4.  * Copyright (c) 2003 Michael Niedermayer
  5.  *
  6.  * This file is part of FFmpeg.
  7.  *
  8.  * FFmpeg is free software; you can redistribute it and/or
  9.  * modify it under the terms of the GNU Lesser General Public
  10.  * License as published by the Free Software Foundation; either
  11.  * version 2.1 of the License, or (at your option) any later version.
  12.  *
  13.  * FFmpeg is distributed in the hope that it will be useful,
  14.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16.  * Lesser General Public License for more details.
  17.  *
  18.  * You should have received a copy of the GNU Lesser General Public
  19.  * License along with FFmpeg; if not, write to the Free Software
  20.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21.  */
  22.  
  23. #include "parser.h"
  24. #include "mpegaudiodecheader.h"
  25. #include "libavutil/common.h"
  26.  
  27.  
  28. typedef struct MpegAudioParseContext {
  29.     ParseContext pc;
  30.     int frame_size;
  31.     uint32_t header;
  32.     int header_count;
  33.     int no_bitrate;
  34. } MpegAudioParseContext;
  35.  
  36. #define MPA_HEADER_SIZE 4
  37.  
  38. /* header + layer + bitrate + freq + lsf/mpeg25 */
  39. #define SAME_HEADER_MASK \
  40.    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
  41.  
  42. static int mpegaudio_parse(AVCodecParserContext *s1,
  43.                            AVCodecContext *avctx,
  44.                            const uint8_t **poutbuf, int *poutbuf_size,
  45.                            const uint8_t *buf, int buf_size)
  46. {
  47.     MpegAudioParseContext *s = s1->priv_data;
  48.     ParseContext *pc = &s->pc;
  49.     uint32_t state= pc->state;
  50.     int i;
  51.     int next= END_NOT_FOUND;
  52.  
  53.     for(i=0; i<buf_size; ){
  54.         if(s->frame_size){
  55.             int inc= FFMIN(buf_size - i, s->frame_size);
  56.             i += inc;
  57.             s->frame_size -= inc;
  58.             state = 0;
  59.  
  60.             if(!s->frame_size){
  61.                 next= i;
  62.                 break;
  63.             }
  64.         }else{
  65.             while(i<buf_size){
  66.                 int ret, sr, channels, bit_rate, frame_size;
  67.  
  68.                 state= (state<<8) + buf[i++];
  69.  
  70.                 ret = avpriv_mpa_decode_header(avctx, state, &sr, &channels, &frame_size, &bit_rate);
  71.                 if (ret < 4) {
  72.                     if (i > 4)
  73.                         s->header_count = -2;
  74.                 } else {
  75.                     if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
  76.                         s->header_count= -3;
  77.                     s->header= state;
  78.                     s->header_count++;
  79.                     s->frame_size = ret-4;
  80.  
  81.                     if (s->header_count > 0) {
  82.                         avctx->sample_rate= sr;
  83.                         avctx->channels   = channels;
  84.                         s1->duration      = frame_size;
  85.                         if (s->no_bitrate || !avctx->bit_rate) {
  86.                             s->no_bitrate = 1;
  87.                             avctx->bit_rate += (bit_rate - avctx->bit_rate) / s->header_count;
  88.                         }
  89.                     }
  90.                     break;
  91.                 }
  92.             }
  93.         }
  94.     }
  95.  
  96.     pc->state= state;
  97.     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  98.         *poutbuf = NULL;
  99.         *poutbuf_size = 0;
  100.         return buf_size;
  101.     }
  102.  
  103.     *poutbuf = buf;
  104.     *poutbuf_size = buf_size;
  105.     return next;
  106. }
  107.  
  108.  
  109. AVCodecParser ff_mpegaudio_parser = {
  110.     .codec_ids      = { AV_CODEC_ID_MP1, AV_CODEC_ID_MP2, AV_CODEC_ID_MP3 },
  111.     .priv_data_size = sizeof(MpegAudioParseContext),
  112.     .parser_parse   = mpegaudio_parse,
  113.     .parser_close   = ff_parse_close,
  114. };
  115.