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mp3_header_compress_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 
26 
27 static int mp3_header_compress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
28  uint8_t **poutbuf, int *poutbuf_size,
29  const uint8_t *buf, int buf_size, int keyframe){
30  uint32_t header, extraheader;
31  int mode_extension, header_size;
32 
34  av_log(avctx, AV_LOG_ERROR, "not standards compliant\n");
35  return -1;
36  }
37 
38  header = AV_RB32(buf);
39  mode_extension= (header>>4)&3;
40 
41  if(ff_mpa_check_header(header) < 0 || (header&0x60000) != 0x20000){
42 output_unchanged:
43  *poutbuf= (uint8_t *) buf;
44  *poutbuf_size= buf_size;
45 
46  av_log(avctx, AV_LOG_INFO, "cannot compress %08X\n", header);
47  return 0;
48  }
49 
50  if(avctx->extradata_size == 0){
51  avctx->extradata_size=15;
52  avctx->extradata= av_malloc(avctx->extradata_size);
53  strcpy(avctx->extradata, "FFCMP3 0.0");
54  memcpy(avctx->extradata+11, buf, 4);
55  }
56  if(avctx->extradata_size != 15){
57  av_log(avctx, AV_LOG_ERROR, "Extradata invalid\n");
58  return -1;
59  }
60  extraheader = AV_RB32(avctx->extradata+11);
61  if((extraheader&MP3_MASK) != (header&MP3_MASK))
62  goto output_unchanged;
63 
64  header_size= (header&0x10000) ? 4 : 6;
65 
66  *poutbuf_size= buf_size - header_size;
67  *poutbuf= av_malloc(buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
68  memcpy(*poutbuf, buf + header_size, buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
69 
70  if(avctx->channels==2){
71  if((header & (3<<19)) != 3<<19){
72  (*poutbuf)[1] &= 0x3F;
73  (*poutbuf)[1] |= mode_extension<<6;
74  FFSWAP(int, (*poutbuf)[1], (*poutbuf)[2]);
75  }else{
76  (*poutbuf)[1] &= 0x8F;
77  (*poutbuf)[1] |= mode_extension<<4;
78  }
79  }
80 
81  return 1;
82 }
83 
85  .name = "mp3comp",
86  .filter = mp3_header_compress,
87 };