libavcodec/aac_ac3_parser.c

   1 /*
   2  * Common AAC and AC3 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 "aac_ac3_parser.h"
  25
  26 int ff_aac_ac3_parse(AVCodecParserContext *s1,
  27                      AVCodecContext *avctx,
  28                      const uint8_t **poutbuf, int *poutbuf_size,
  29                      const uint8_t *buf, int buf_size)
  30 {
  31     AACAC3ParseContext *s = s1->priv_data;
  32     ParseContext *pc = &s->pc;
  33     int len, i;
  34
  35     while(s->remaining_size <= buf_size){
  36         if(s->remaining_size && !s->need_next_header){
  37             i= s->remaining_size;
  38             s->remaining_size = 0;
  39             goto output_frame;
  40         }else{ //we need a header first
  41             len=0;
  42             for(i=s->remaining_size; i<buf_size; i++){
  43                 s->state = (s->state<<8) + buf[i];
  44                 if((len=s->sync(s->state, s, &s->need_next_header, &s->new_frame_start)))
  45                     break;
  46             }
  47             i-= s->header_size -1;
  48             if(len>0){
  49                 s->remaining_size = len + i;
  50
  51                 if(pc->index+i > 0 && s->new_frame_start){
  52                     s->remaining_size -= i; // remaining_size=len
  53 output_frame:
  54                     if(!s->frame_in_buffer){
  55                         s->frame_in_buffer=1;
  56                         buf+=i;
  57                         buf_size-=i;
  58                         continue;
  59                     }
  60                     ff_combine_frame(pc, i, &buf, &buf_size);
  61                     *poutbuf = buf;
  62                     *poutbuf_size = buf_size;
  63
  64                     /* update codec info */
  65                     avctx->sample_rate = s->sample_rate;
  66                     /* allow downmixing to stereo (or mono for AC3) */
  67                     if(avctx->request_channels > 0 &&
  68                             avctx->request_channels < s->channels &&
  69                             (avctx->request_channels <= 2 ||
  70                             (avctx->request_channels == 1 &&
  71                             avctx->codec_id == CODEC_ID_AC3))) {
  72                         avctx->channels = avctx->request_channels;
  73                     } else {
  74                         avctx->channels = s->channels;
  75                     }
  76                     avctx->bit_rate = s->bit_rate;
  77                     avctx->frame_size = s->samples;
  78
  79                     return i;
  80                 }
  81                 s->frame_in_buffer=1;
  82             }else{
  83                 break;
  84             }
  85         }
  86     }
  87
  88     ff_combine_frame(pc, END_NOT_FOUND, &buf, &buf_size);
  89     s->remaining_size -= FFMIN(s->remaining_size, buf_size);
  90     *poutbuf = NULL;
  91     *poutbuf_size = 0;
  92     return buf_size;
  93 }