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
99
|
/*
Handling of MPEG Audio Headers.
*/
#include <stdio.h>
#include <stdlib.h>
#include "mp3info.h"
char *mode_names[5] = { "stereo", "j-stereo", "dual-ch", "single-ch" , "multi-ch"};
char *layer_names[3] = { "I", "II", "III" };
char *version_names[3] = { "MPEG-1", "MPEG-2 LSF", "MPEG-2.5" };
char *version_nums[3] = { "1", "2", "2.5" };
unsigned int bitrates[3][3][15] = {
{
{0,32,64,96,128,160,192,224,256,288,320,352,384,416,448},
{0,32,48,56,64,80,96,112,128,160,192,224,256,320,384},
{0,32,40,48,56,64,80,96,112,128,160,192,224,256,320}
},{
{0,32,48,56,64,80,96,112,128,144,160,176,192,224,256},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160}
},{
{0,32,48,56,64,80,96,112,128,144,160,176,192,224,256},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160},
{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160}
}};
unsigned int s_freq[3][4] = {
{44100, 48000, 32000, 0},
{22050, 24000, 16000, 0},
{11025, 8000, 8000, 0}
};
char *Layer::mode_name() {
return(mode_names[mode]);
}
char *Layer::layer_name() {
return(layer_names[lay-1]);
}
char *Layer::version_name() {
return(version_names[version]);
}
char *Layer::version_num() {
return(version_nums[version]);
}
unsigned int Layer::bitrate() {
return(bitrates[version][lay-1][bitrate_index]);
}
unsigned int Layer::sfreq() {
return(s_freq[version][sampling_frequency]);
}
bool Layer::get(FILE *file) {
unsigned char buffer[5];
size_t temp;
fseek(file, 0, SEEK_SET) ;
temp=fread(&buffer,4,1,file);
temp=((buffer[0]<<4) & 0xFF0) | ((buffer[1]>>4) & 0xE);
if (temp != 0xFFE) {
return(false);
} else {
switch((buffer[1]>>2 & 0x3)) {
case 2:
version = 0;
break;
case 3:
version = 1;
break;
case 0:
version = 2;
break;
default:
return(false);
}
lay = 4-((buffer[1]>>1) & 0x3);
error_protection = !(buffer[1] & 0x1);
bitrate_index = (buffer[2]>>4) & 0x0F;
sampling_frequency = (buffer[2]>>2) & 0x3;
padding = (buffer[2]>>1) & 0x01;
extension = buffer[2] & 0x01;
mode = (buffer[3]>>6) & 0x3;
mode_ext = (buffer[3]>>4) & 0x03;
copyright = (buffer[3]>>3) & 0x01;
original = (buffer[3]>>2) & 0x1;
emphasis = ( buffer[3] ) & 0x3;
stereo = (mode == MPG_MD_MONO) ? 1 : 2;
return(true);
}
}
|
