mp3_header_decompress_bsf.c 3.2 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
/*
 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
 *
 * 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
 */

21
#include "libavutil/common.h"
22
#include "libavutil/intreadwrite.h"
23
#include "avcodec.h"
24
#include "mpegaudiodecheader.h"
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
#include "mpegaudiodata.h"


static int mp3_header_decompress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
                     uint8_t **poutbuf, int *poutbuf_size,
                     const uint8_t *buf, int buf_size, int keyframe){
    uint32_t header;
    int sample_rate= avctx->sample_rate;
    int sample_rate_index=0;
    int lsf, mpeg25, bitrate_index, frame_size;

    header = AV_RB32(buf);
    if(ff_mpa_check_header(header) >= 0){
        *poutbuf= (uint8_t *) buf;
        *poutbuf_size= buf_size;

        return 0;
    }

    if(avctx->extradata_size != 15 || strcmp(avctx->extradata, "FFCMP3 0.0")){
        av_log(avctx, AV_LOG_ERROR, "Extradata invalid %d\n", avctx->extradata_size);
        return -1;
    }

    header= AV_RB32(avctx->extradata+11) & MP3_MASK;

    lsf     = sample_rate < (24000+32000)/2;
    mpeg25  = sample_rate < (12000+16000)/2;
    sample_rate_index= (header>>10)&3;
54
    sample_rate= avpriv_mpa_freq_tab[sample_rate_index] >> (lsf + mpeg25); //in case sample rate is a little off
55 56

    for(bitrate_index=2; bitrate_index<30; bitrate_index++){
57
        frame_size = avpriv_mpa_bitrate_tab[lsf][2][bitrate_index>>1];
58 59 60 61 62 63 64
        frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
        if(frame_size == buf_size + 4)
            break;
        if(frame_size == buf_size + 6)
            break;
    }
    if(bitrate_index == 30){
Diego Biurrun's avatar
Diego Biurrun committed
65
        av_log(avctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
        return -1;
    }

    header |= (bitrate_index&1)<<9;
    header |= (bitrate_index>>1)<<12;
    header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0

    *poutbuf_size= frame_size;
    *poutbuf= av_malloc(frame_size + FF_INPUT_BUFFER_PADDING_SIZE);
    memcpy(*poutbuf + frame_size - buf_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);

    if(avctx->channels==2){
        uint8_t *p= *poutbuf + frame_size - buf_size;
        if(lsf){
            FFSWAP(int, p[1], p[2]);
            header |= (p[1] & 0xC0)>>2;
            p[1] &= 0x3F;
        }else{
            header |= p[1] & 0x30;
            p[1] &= 0xCF;
        }
    }

89
    AV_WB32(*poutbuf, header);
90 91 92 93

    return 1;
}

94
AVBitStreamFilter ff_mp3_header_decompress_bsf={
95 96 97 98
    "mp3decomp",
    0,
    mp3_header_decompress,
};