libavcodec/mpegaudio_parser.c

   1 /*
   2  * MPEG Audio parser
   3  * Copyright (c) 2003 Fabrice Bellard
   4  * Copyright (c) 2003 Michael Niedermayer
   5  *
   6  * This file is part of Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; 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
  26
  27 typedef struct MpegAudioParseContext {
  28     ParseContext pc;
  29     int frame_size;
  30     uint32_t header;
  31     int header_count;
  32 } MpegAudioParseContext;
  33
  34 #define MPA_HEADER_SIZE 4
  35
  36 /* header + layer + bitrate + freq + lsf/mpeg25 */
  37 #define SAME_HEADER_MASK \
  38    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
  39
  40 static int mpegaudio_parse(AVCodecParserContext *s1,
  41                            AVCodecContext *avctx,
  42                            const uint8_t **poutbuf, int *poutbuf_size,
  43                            const uint8_t *buf, int buf_size)
  44 {
  45     MpegAudioParseContext *s = s1->priv_data;
  46     ParseContext *pc = &s->pc;
  47     uint32_t state= pc->state;
  48     int i;
  49     int next= END_NOT_FOUND;
  50
  51     for(i=0; i<buf_size; ){
  52         if(s->frame_size){
  53             int inc= FFMIN(buf_size - i, s->frame_size);
  54             i += inc;
  55             s->frame_size -= inc;
  56
  57             if(!s->frame_size){
  58                 next= i;
  59                 break;
  60             }
  61         }else{
  62             while(i<buf_size){
  63                 int ret, sr, channels, bit_rate, frame_size;
  64
  65                 state= (state<<8) + buf[i++];
  66
  67                 ret = avpriv_mpa_decode_header(avctx, state, &sr, &channels, &frame_size, &bit_rate);
  68                 if (ret < 4) {
  69                     if (i > 4)
  70                         s->header_count = -2;
  71                 } else {
  72                     if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
  73                         s->header_count= -3;
  74                     s->header= state;
  75                     s->header_count++;
  76                     s->frame_size = ret-4;
  77
  78                     if (s->header_count > 0) {
  79                         avctx->sample_rate= sr;
  80                         avctx->channels   = channels;
  81                         s1->duration      = frame_size;
  82                         avctx->bit_rate   = bit_rate;
  83                     }
  84                     break;
  85                 }
  86             }
  87         }
  88     }
  89
  90     pc->state= state;
  91     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  92         *poutbuf = NULL;
  93         *poutbuf_size = 0;
  94         return buf_size;
  95     }
  96
  97     *poutbuf = buf;
  98     *poutbuf_size = buf_size;
  99     return next;
 100 }
 101
 102
 103 AVCodecParser ff_mpegaudio_parser = {
 104     .codec_ids      = { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 },
 105     .priv_data_size = sizeof(MpegAudioParseContext),
 106     .parser_parse   = mpegaudio_parse,
 107     .parser_close   = ff_parse_close,
 108 };