ffmpeg/libavcodec/aac_ac3_parser.c

/*
 * Common AAC and AC-3 parser
 * Copyright (c) 2003 Fabrice Bellard.
 * Copyright (c) 2003 Michael Niedermayer.
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "parser.h"
#include "aac_ac3_parser.h"

int ff_aac_ac3_parse(AVCodecParserContext *s1,
                     AVCodecContext *avctx,
                     const uint8_t **poutbuf, int *poutbuf_size,
                     const uint8_t *buf, int buf_size)
{
    AACAC3ParseContext *s = s1->priv_data;
    ParseContext *pc = &s->pc;
    int len, i;
    int new_frame_start;

get_next:
    i=END_NOT_FOUND;
    if(s->remaining_size <= buf_size){
        if(s->remaining_size && !s->need_next_header){
            i= s->remaining_size;
            s->remaining_size = 0;
        }else{ //we need a header first
            len=0;
            for(i=s->remaining_size; i<buf_size; i++){
                s->state = (s->state<<8) + buf[i];
                if((len=s->sync(s->state, s, &s->need_next_header, &new_frame_start)))
                    break;
            }
            if(len<=0){
                i=END_NOT_FOUND;
            }else{
                s->state=0;
                i-= s->header_size -1;
                s->remaining_size = len;
                if(!new_frame_start || pc->index+i<=0){
                    s->remaining_size += i;
                    goto get_next;
                }
            }
        }
    }

    if(ff_combine_frame(pc, i, &buf, &buf_size)<0){
        s->remaining_size -= FFMIN(s->remaining_size, buf_size);
        *poutbuf = NULL;
        *poutbuf_size = 0;
        return buf_size;
    }

    *poutbuf = buf;
    *poutbuf_size = buf_size;

    /* update codec info */
    avctx->sample_rate = s->sample_rate;
    /* allow downmixing to stereo (or mono for AC-3) */
    if(avctx->request_channels > 0 &&
            avctx->request_channels < s->channels &&
            (avctx->request_channels <= 2 ||
            (avctx->request_channels == 1 &&
            (avctx->codec_id == CODEC_ID_AC3 ||
             avctx->codec_id == CODEC_ID_EAC3)))) {
        avctx->channels = avctx->request_channels;
    } else {
        avctx->channels = s->channels;
    }
    avctx->bit_rate = s->bit_rate;
    avctx->frame_size = s->samples;

    return i;
}