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 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/intreadwrite.h"
22 #include "avcodec.h"
23 #include "mpegaudiodecheader.h"
24 #include "mpegaudiodata.h"
25 
26 
27 static int mp3_header_decompress(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;
31  int sample_rate= avctx->sample_rate;
32  int sample_rate_index=0;
33  int lsf, mpeg25, bitrate_index, frame_size;
34 
35  header = AV_RB32(buf);
36  if(ff_mpa_check_header(header) >= 0){
37  *poutbuf= (uint8_t *) buf;
38  *poutbuf_size= buf_size;
39 
40  return 0;
41  }
42 
43  if(avctx->extradata_size != 15 || strcmp(avctx->extradata, "FFCMP3 0.0")){
44  av_log(avctx, AV_LOG_ERROR, "Extradata invalid %d\n", avctx->extradata_size);
45  return -1;
46  }
47 
48  header= AV_RB32(avctx->extradata+11) & MP3_MASK;
49 
50  lsf = sample_rate < (24000+32000)/2;
51  mpeg25 = sample_rate < (12000+16000)/2;
52  sample_rate_index= (header>>10)&3;
53  sample_rate= avpriv_mpa_freq_tab[sample_rate_index] >> (lsf + mpeg25); //in case sample rate is a little off
54 
55  for(bitrate_index=2; bitrate_index<30; bitrate_index++){
56  frame_size = avpriv_mpa_bitrate_tab[lsf][2][bitrate_index>>1];
57  frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
58  if(frame_size == buf_size + 4)
59  break;
60  if(frame_size == buf_size + 6)
61  break;
62  }
63  if(bitrate_index == 30){
64  av_log(avctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
65  return -1;
66  }
67 
68  header |= (bitrate_index&1)<<9;
69  header |= (bitrate_index>>1)<<12;
70  header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0
71 
72  *poutbuf_size= frame_size;
73  *poutbuf= av_malloc(frame_size + FF_INPUT_BUFFER_PADDING_SIZE);
74  memcpy(*poutbuf + frame_size - buf_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
75 
76  if(avctx->channels==2){
77  uint8_t *p= *poutbuf + frame_size - buf_size;
78  if(lsf){
79  FFSWAP(int, p[1], p[2]);
80  header |= (p[1] & 0xC0)>>2;
81  p[1] &= 0x3F;
82  }else{
83  header |= p[1] & 0x30;
84  p[1] &= 0xCF;
85  }
86  }
87 
88  AV_WB32(*poutbuf, header);
89 
90  return 1;
91 }
92 
94  "mp3decomp",
95  0,
97 };
AV_WL32 AV_WL24 AV_WL16 AV_RB32
Definition: bytestream.h:89
#define MP3_MASK
mpeg audio layer common tables.
#define AV_WB32(p, d)
Definition: intreadwrite.h:239
const uint16_t avpriv_mpa_freq_tab[3]
Definition: mpegaudiodata.c:40
uint8_t * extradata
some codecs need / can use extradata like Huffman tables.
Definition: avcodec.h:1387
void av_log(void *avcl, int level, const char *fmt,...)
Definition: log.c:140
static int mp3_header_decompress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args, uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size, int keyframe)
static int ff_mpa_check_header(uint32_t header)
external API header
int sample_rate
samples per second
Definition: avcodec.h:1456
main external API structure.
Definition: avcodec.h:1329
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:111
int extradata_size
Definition: avcodec.h:1388
void * av_malloc(size_t size)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:64
AVBitStreamFilter ff_mp3_header_decompress_bsf
#define FF_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding...
Definition: avcodec.h:497
MPEG Audio header decoder.
int channels
number of audio channels
Definition: avcodec.h:1457
const uint16_t avpriv_mpa_bitrate_tab[2][3][15]
Definition: mpegaudiodata.c:30
#define FFSWAP(type, a, b)
Definition: common.h:58