libavcodec/mp3_header_decompress_bsf.c

   1 /*
   2  * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of Libav.
   5  *
   6  * Libav 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  * Libav 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 Libav; 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     "mp3decomp",
  96     0,
  97     mp3_header_decompress,
  98 };