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 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 "mpegaudio.h"
  25 #include "mpegaudiodecheader.h"
  26
  27
  28 typedef struct MpegAudioParseContext {
  29     ParseContext pc;
  30     int frame_size;
  31     uint32_t header;
  32     int header_count;
  33 } MpegAudioParseContext;
  34
  35 #define MPA_HEADER_SIZE 4
  36
  37 /* header + layer + bitrate + freq + lsf/mpeg25 */
  38 #undef SAME_HEADER_MASK /* mpegaudio.h defines different version */
  39 #define SAME_HEADER_MASK \
  40    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
  41
  42 /* useful helper to get mpeg audio stream infos. Return -1 if error in
  43    header, otherwise the coded frame size in bytes */
  44 int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate)
  45 {
  46     MPADecodeHeader s1, *s = &s1;
  47
  48     if (ff_mpa_check_header(head) != 0)
  49         return -1;
  50
  51     if (ff_mpegaudio_decode_header(s, head) != 0) {
  52         return -1;
  53     }
  54
  55     switch(s->layer) {
  56     case 1:
  57         avctx->codec_id = CODEC_ID_MP1;
  58         *frame_size = 384;
  59         break;
  60     case 2:
  61         avctx->codec_id = CODEC_ID_MP2;
  62         *frame_size = 1152;
  63         break;
  64     default:
  65     case 3:
  66         avctx->codec_id = CODEC_ID_MP3;
  67         if (s->lsf)
  68             *frame_size = 576;
  69         else
  70             *frame_size = 1152;
  71         break;
  72     }
  73
  74     *sample_rate = s->sample_rate;
  75     *channels = s->nb_channels;
  76     *bit_rate = s->bit_rate;
  77     avctx->sub_id = s->layer;
  78     return s->frame_size;
  79 }
  80
  81 static int mpegaudio_parse(AVCodecParserContext *s1,
  82                            AVCodecContext *avctx,
  83                            const uint8_t **poutbuf, int *poutbuf_size,
  84                            const uint8_t *buf, int buf_size)
  85 {
  86     MpegAudioParseContext *s = s1->priv_data;
  87     ParseContext *pc = &s->pc;
  88     uint32_t state= pc->state;
  89     int i;
  90     int next= END_NOT_FOUND;
  91
  92     for(i=0; i<buf_size; ){
  93         if(s->frame_size){
  94             int inc= FFMIN(buf_size - i, s->frame_size);
  95             i += inc;
  96             s->frame_size -= inc;
  97
  98             if(!s->frame_size){
  99                 next= i;
 100                 break;
 101             }
 102         }else{
 103             while(i<buf_size){
 104                 int ret, sr, channels, bit_rate, frame_size;
 105
 106                 state= (state<<8) + buf[i++];
 107
 108                 ret = ff_mpa_decode_header(avctx, state, &sr, &channels, &frame_size, &bit_rate);
 109                 if (ret < 4) {
 110                     s->header_count= -2;
 111                 } else {
 112                     if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
 113                         s->header_count= -3;
 114                     s->header= state;
 115                     s->header_count++;
 116                     s->frame_size = ret-4;
 117
 118                     if(s->header_count > 1){
 119                         avctx->sample_rate= sr;
 120                         avctx->channels   = channels;
 121                         avctx->frame_size = frame_size;
 122                         avctx->bit_rate   = bit_rate;
 123                     }
 124                     break;
 125                 }
 126             }
 127         }
 128     }
 129
 130     pc->state= state;
 131     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 132         *poutbuf = NULL;
 133         *poutbuf_size = 0;
 134         return buf_size;
 135     }
 136
 137     *poutbuf = buf;
 138     *poutbuf_size = buf_size;
 139     return next;
 140 }
 141
 142
 143 AVCodecParser mpegaudio_parser = {
 144     { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 },
 145     sizeof(MpegAudioParseContext),
 146     NULL,
 147     mpegaudio_parse,
 148     ff_parse_close,
 149 };