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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     avctx->sample_rate = s->sample_rate;
00075     if(s->codec_id)
00076         avctx->codec_id = s->codec_id;
00077 
00078     /* allow downmixing to stereo (or mono for AC-3) */
00079     if(avctx->request_channels > 0 &&
00080             avctx->request_channels < s->channels &&
00081             (avctx->request_channels <= 2 ||
00082             (avctx->request_channels == 1 &&
00083             (avctx->codec_id == CODEC_ID_AC3 ||
00084              avctx->codec_id == CODEC_ID_EAC3)))) {
00085         avctx->channels = avctx->request_channels;
00086     } else {
00087         avctx->channels = s->channels;
00088     }
00089     avctx->bit_rate = s->bit_rate;
00090     avctx->frame_size = s->samples;
00091 
00092     return i;
00093 }

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