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ffmpeg / libavformat / aacdec.c @ 2912e87a

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/*
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 * raw ADTS AAC demuxer
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 * Copyright (c) 2008 Michael Niedermayer <michaelni@gmx.at>
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 * Copyright (c) 2009 Robert Swain ( rob opendot cl )
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 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "libavutil/intreadwrite.h"
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#include "avformat.h"
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#include "rawdec.h"
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#include "id3v1.h"
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static int adts_aac_probe(AVProbeData *p)
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{
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    int max_frames = 0, first_frames = 0;
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    int fsize, frames;
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    uint8_t *buf0 = p->buf;
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    uint8_t *buf2;
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    uint8_t *buf;
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    uint8_t *end = buf0 + p->buf_size - 7;
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    buf = buf0;
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    for(; buf < end; buf= buf2+1) {
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        buf2 = buf;
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        for(frames = 0; buf2 < end; frames++) {
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            uint32_t header = AV_RB16(buf2);
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            if((header&0xFFF6) != 0xFFF0)
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                break;
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            fsize = (AV_RB32(buf2+3)>>13) & 0x8FFF;
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            if(fsize < 7)
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                break;
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            buf2 += fsize;
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        }
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        max_frames = FFMAX(max_frames, frames);
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        if(buf == buf0)
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            first_frames= frames;
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    }
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    if   (first_frames>=3) return AVPROBE_SCORE_MAX/2+1;
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    else if(max_frames>500)return AVPROBE_SCORE_MAX/2;
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    else if(max_frames>=3) return AVPROBE_SCORE_MAX/4;
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    else if(max_frames>=1) return 1;
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    else                   return 0;
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}
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static int adts_aac_read_header(AVFormatContext *s,
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                                AVFormatParameters *ap)
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{
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    AVStream *st;
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    st = av_new_stream(s, 0);
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    if (!st)
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        return AVERROR(ENOMEM);
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    st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
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    st->codec->codec_id = s->iformat->value;
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    st->need_parsing = AVSTREAM_PARSE_FULL;
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    ff_id3v1_read(s);
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    //LCM of all possible ADTS sample rates
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    av_set_pts_info(st, 64, 1, 28224000);
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    return 0;
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}
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AVInputFormat ff_aac_demuxer = {
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    "aac",
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    NULL_IF_CONFIG_SMALL("raw ADTS AAC"),
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    0,
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    adts_aac_probe,
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    adts_aac_read_header,
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    ff_raw_read_partial_packet,
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    .flags= AVFMT_GENERIC_INDEX,
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    .extensions = "aac",
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    .value = CODEC_ID_AAC,
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};