1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
|
/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2005 Dave Chapman
*
* All files in this archive are subject to the GNU General Public License.
* See the file COPYING in the source tree root for full license agreement.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#include "id3.h"
#include "logf.h"
static const unsigned short a52_bitrates[] =
{
32, 40, 48, 56, 64, 80, 96, 112, 128, 160,
192, 224, 256, 320, 384, 448, 512, 576, 640
};
/* Only store frame sizes for 44.1KHz - others are simply multiples
of the bitrate */
static const unsigned short a52_441framesizes[] =
{
69 * 2, 70 * 2, 87 * 2, 88 * 2, 104 * 2, 105 * 2, 121 * 2,
122 * 2, 139 * 2, 140 * 2, 174 * 2, 175 * 2, 208 * 2, 209 * 2,
243 * 2, 244 * 2, 278 * 2, 279 * 2, 348 * 2, 349 * 2, 417 * 2,
418 * 2, 487 * 2, 488 * 2, 557 * 2, 558 * 2, 696 * 2, 697 * 2,
835 * 2, 836 * 2, 975 * 2, 976 * 2, 1114 * 2, 1115 * 2, 1253 * 2,
1254 * 2, 1393 * 2, 1394 * 2
};
bool get_a52_metadata(int fd, struct mp3entry *id3)
{
/* Use the trackname part of the id3 structure as a temporary buffer */
unsigned char* buf = (unsigned char *)id3->path;
unsigned long totalsamples;
int i;
if ((lseek(fd, 0, SEEK_SET) < 0) || (read(fd, buf, 5) < 5))
{
return false;
}
if ((buf[0] != 0x0b) || (buf[1] != 0x77))
{
logf("not an A52/AC3 file\n");
return false;
}
i = buf[4] & 0x3e;
if (i > 36)
{
logf("A52: Invalid frmsizecod: %d\n",i);
return false;
}
id3->bitrate = a52_bitrates[i >> 1];
id3->vbr = false;
id3->filesize = filesize(fd);
switch (buf[4] & 0xc0)
{
case 0x00:
id3->frequency = 48000;
id3->bytesperframe=id3->bitrate * 2 * 2;
break;
case 0x40:
id3->frequency = 44100;
id3->bytesperframe = a52_441framesizes[i];
break;
case 0x80:
id3->frequency = 32000;
id3->bytesperframe = id3->bitrate * 3 * 2;
break;
default:
logf("A52: Invalid samplerate code: 0x%02x\n", buf[4] & 0xc0);
return false;
break;
}
/* One A52 frame contains 6 blocks, each containing 256 samples */
totalsamples = id3->filesize / id3->bytesperframe * 6 * 256;
id3->length = totalsamples / id3->frequency * 1000;
return true;
}
|
