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mp3_header_decompress_bsf.c
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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 
95  .name = "mp3decomp",
96  .filter = mp3_header_decompress,
97 };