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     const uint8_t *buf_ptr;
  33     int len, sample_rate, bit_rate, channels, samples;
  34
  35     *poutbuf = NULL;
  36     *poutbuf_size = 0;
  37
  38     buf_ptr = buf;
  39     while (buf_size > 0) {
  40         len = s->inbuf_ptr - s->inbuf;
  41         if (s->frame_size == 0) {
  42             /* no header seen : find one. We need at least s->header_size
  43                bytes to parse it */
  44             len = FFMIN(s->header_size - len, buf_size);
  45
  46             memcpy(s->inbuf_ptr, buf_ptr, len);
  47             buf_ptr += len;
  48             s->inbuf_ptr += len;
  49             buf_size -= len;
  50             if ((s->inbuf_ptr - s->inbuf) == s->header_size) {
  51                 len = s->sync(s->inbuf, &channels, &sample_rate, &bit_rate,
  52                               &samples);
  53                 if (len == 0) {
  54                     /* no sync found : move by one byte (inefficient, but simple!) */
  55                     memmove(s->inbuf, s->inbuf + 1, s->header_size - 1);
  56                     s->inbuf_ptr--;
  57                 } else {
  58                     s->frame_size = len;
  59                     /* update codec info */
  60                     avctx->sample_rate = sample_rate;
  61                     /* set channels,except if the user explicitly requests 1 or 2 channels, XXX/FIXME this is a bit ugly */
  62                     if(avctx->codec_id == CODEC_ID_AC3){
  63                         if(avctx->channels!=1 && avctx->channels!=2){
  64                             avctx->channels = channels;
  65                         }
  66                     } else {
  67                         avctx->channels = channels;
  68                     }
  69                     avctx->bit_rate = bit_rate;
  70                     avctx->frame_size = samples;
  71                 }
  72             }
  73         } else {
  74             len = FFMIN(s->frame_size - len, buf_size);
  75
  76             memcpy(s->inbuf_ptr, buf_ptr, len);
  77             buf_ptr += len;
  78             s->inbuf_ptr += len;
  79             buf_size -= len;
  80
  81             if(s->inbuf_ptr - s->inbuf == s->frame_size){
  82                 *poutbuf = s->inbuf;
  83                 *poutbuf_size = s->frame_size;
  84                 s->inbuf_ptr = s->inbuf;
  85                 s->frame_size = 0;
  86                 break;
  87             }
  88         }
  89     }
  90     return buf_ptr - buf;
  91 }