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  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 "libavutil/common.h"
  22. #include "libavutil/intreadwrite.h"
  23. #include "avcodec.h"
  24. #include "mpegaudiodecheader.h"
  25. #include "mpegaudiodata.h"
  26.  
  27.  
  28. static int mp3_header_decompress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
  29.                      uint8_t **poutbuf, int *poutbuf_size,
  30.                      const uint8_t *buf, int buf_size, int keyframe){
  31.     uint32_t header;
  32.     int sample_rate= avctx->sample_rate;
  33.     int sample_rate_index=0;
  34.     int lsf, mpeg25, bitrate_index, frame_size;
  35.  
  36.     header = AV_RB32(buf);
  37.     if(ff_mpa_check_header(header) >= 0){
  38.         *poutbuf= (uint8_t *) buf;
  39.         *poutbuf_size= buf_size;
  40.  
  41.         return 0;
  42.     }
  43.  
  44.     if(avctx->extradata_size != 15 || strcmp(avctx->extradata, "FFCMP3 0.0")){
  45.         av_log(avctx, AV_LOG_ERROR, "Extradata invalid %d\n", avctx->extradata_size);
  46.         return -1;
  47.     }
  48.  
  49.     header= AV_RB32(avctx->extradata+11) & MP3_MASK;
  50.  
  51.     lsf     = sample_rate < (24000+32000)/2;
  52.     mpeg25  = sample_rate < (12000+16000)/2;
  53.     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.         frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
  59.         if(frame_size == buf_size + 4)
  60.             break;
  61.         if(frame_size == buf_size + 6)
  62.             break;
  63.     }
  64.     if(bitrate_index == 30){
  65.         av_log(avctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
  66.         return -1;
  67.     }
  68.  
  69.     header |= (bitrate_index&1)<<9;
  70.     header |= (bitrate_index>>1)<<12;
  71.     header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0
  72.  
  73.     *poutbuf_size= frame_size;
  74.     *poutbuf= av_malloc(frame_size + FF_INPUT_BUFFER_PADDING_SIZE);
  75.     memcpy(*poutbuf + frame_size - buf_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
  76.  
  77.     if(avctx->channels==2){
  78.         uint8_t *p= *poutbuf + frame_size - buf_size;
  79.         if(lsf){
  80.             FFSWAP(int, p[1], p[2]);
  81.             header |= (p[1] & 0xC0)>>2;
  82.             p[1] &= 0x3F;
  83.         }else{
  84.             header |= p[1] & 0x30;
  85.             p[1] &= 0xCF;
  86.         }
  87.     }
  88.  
  89.     AV_WB32(*poutbuf, header);
  90.  
  91.     return 1;
  92. }
  93.  
  94. AVBitStreamFilter ff_mp3_header_decompress_bsf={
  95.     .name   = "mp3decomp",
  96.     .filter = mp3_header_decompress,
  97. };
  98.