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libavcodec/aac_ac3_parser.c

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00001 /*
00002  * Common AAC and AC-3 parser
00003  * Copyright (c) 2003 Fabrice Bellard
00004  * Copyright (c) 2003 Michael Niedermayer
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * FFmpeg is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "parser.h"
00024 #include "aac_ac3_parser.h"
00025 
00026 int ff_aac_ac3_parse(AVCodecParserContext *s1,
00027                      AVCodecContext *avctx,
00028                      const uint8_t **poutbuf, int *poutbuf_size,
00029                      const uint8_t *buf, int buf_size)
00030 {
00031     AACAC3ParseContext *s = s1->priv_data;
00032     ParseContext *pc = &s->pc;
00033     int len, i;
00034     int new_frame_start;
00035 
00036 get_next:
00037     i=END_NOT_FOUND;
00038     if(s->remaining_size <= buf_size){
00039         if(s->remaining_size && !s->need_next_header){
00040             i= s->remaining_size;
00041             s->remaining_size = 0;
00042         }else{ //we need a header first
00043             len=0;
00044             for(i=s->remaining_size; i<buf_size; i++){
00045                 s->state = (s->state<<8) + buf[i];
00046                 if((len=s->sync(s->state, s, &s->need_next_header, &new_frame_start)))
00047                     break;
00048             }
00049             if(len<=0){
00050                 i=END_NOT_FOUND;
00051             }else{
00052                 s->state=0;
00053                 i-= s->header_size -1;
00054                 s->remaining_size = len;
00055                 if(!new_frame_start || pc->index+i<=0){
00056                     s->remaining_size += i;
00057                     goto get_next;
00058                 }
00059             }
00060         }
00061     }
00062 
00063     if(ff_combine_frame(pc, i, &buf, &buf_size)<0){
00064         s->remaining_size -= FFMIN(s->remaining_size, buf_size);
00065         *poutbuf = NULL;
00066         *poutbuf_size = 0;
00067         return buf_size;
00068     }
00069 
00070     *poutbuf = buf;
00071     *poutbuf_size = buf_size;
00072 
00073     /* update codec info */
00074     if(s->codec_id)
00075         avctx->codec_id = s->codec_id;
00076 
00077     /* Due to backwards compatible HE-AAC the sample rate, channel count,
00078        and total number of samples found in an AAC ADTS header are not
00079        reliable. Bit rate is still accurate because the total frame duration in
00080        seconds is still correct (as is the number of bits in the frame). */
00081     if (avctx->codec_id != CODEC_ID_AAC) {
00082         avctx->sample_rate = s->sample_rate;
00083 
00084         /* allow downmixing to stereo (or mono for AC-3) */
00085         if(avctx->request_channels > 0 &&
00086                 avctx->request_channels < s->channels &&
00087                 (avctx->request_channels <= 2 ||
00088                 (avctx->request_channels == 1 &&
00089                 (avctx->codec_id == CODEC_ID_AC3 ||
00090                  avctx->codec_id == CODEC_ID_EAC3)))) {
00091             avctx->channels = avctx->request_channels;
00092         } else {
00093             avctx->channels = s->channels;
00094             avctx->channel_layout = s->channel_layout;
00095         }
00096         avctx->frame_size = s->samples;
00097     }
00098 
00099     avctx->bit_rate = s->bit_rate;
00100 
00101     return i;
00102 }

Generated on Fri Sep 16 2011 17:17:32 for FFmpeg by  doxygen 1.7.1