libavcodec/mp3_header_decompress_bsf.c

   1 /*
   2  * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include "avcodec.h"
  22 #include "mpegaudio.h"
  23 #include "mpegaudiodata.h"
  24
  25
  26 static int mp3_header_decompress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
  27                      uint8_t **poutbuf, int *poutbuf_size,
  28                      const uint8_t *buf, int buf_size, int keyframe){
  29     uint32_t header;
  30     int sample_rate= avctx->sample_rate;
  31     int sample_rate_index=0;
  32     int lsf, mpeg25, bitrate_index, frame_size;
  33
  34     header = AV_RB32(buf);
  35     if(ff_mpa_check_header(header) >= 0){
  36         *poutbuf= (uint8_t *) buf;
  37         *poutbuf_size= buf_size;
  38
  39         return 0;
  40     }
  41
  42     if(avctx->extradata_size != 15 || strcmp(avctx->extradata, "FFCMP3 0.0")){
  43         av_log(avctx, AV_LOG_ERROR, "Extradata invalid %d\n", avctx->extradata_size);
  44         return -1;
  45     }
  46
  47     header= AV_RB32(avctx->extradata+11) & MP3_MASK;
  48
  49     lsf     = sample_rate < (24000+32000)/2;
  50     mpeg25  = sample_rate < (12000+16000)/2;
  51     sample_rate_index= (header>>10)&3;
  52     sample_rate= ff_mpa_freq_tab[sample_rate_index] >> (lsf + mpeg25); //in case sample rate is a little off
  53
  54     for(bitrate_index=2; bitrate_index<30; bitrate_index++){
  55         frame_size = ff_mpa_bitrate_tab[lsf][2][bitrate_index>>1];
  56         frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
  57         if(frame_size == buf_size + 4)
  58             break;
  59         if(frame_size == buf_size + 6)
  60             break;
  61     }
  62     if(bitrate_index == 30){
  63         av_log(avctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
  64         return -1;
  65     }
  66
  67     header |= (bitrate_index&1)<<9;
  68     header |= (bitrate_index>>1)<<12;
  69     header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0
  70
  71     *poutbuf_size= frame_size;
  72     *poutbuf= av_malloc(frame_size + FF_INPUT_BUFFER_PADDING_SIZE);
  73     memcpy(*poutbuf + frame_size - buf_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
  74
  75     if(avctx->channels==2){
  76         uint8_t *p= *poutbuf + frame_size - buf_size;
  77         if(lsf){
  78             FFSWAP(int, p[1], p[2]);
  79             header |= (p[1] & 0xC0)>>2;
  80             p[1] &= 0x3F;
  81         }else{
  82             header |= p[1] & 0x30;
  83             p[1] &= 0xCF;
  84         }
  85     }
  86
  87     AV_WB32(*poutbuf, header);
  88
  89     return 1;
  90 }
  91
  92 AVBitStreamFilter mp3_header_decompress_bsf={
  93     "mp3decomp",
  94     0,
  95     mp3_header_decompress,
  96 };