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
100
101
102
|
/* Pre-Emphasis and De-Emphasis implementation
*
* (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
* All Rights Reserved
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <math.h>
#include "emphasis.h"
#include "debug.h"
int init_emphasis(emphasis_t *state, int samplerate)
{
double factor;
memset(state, 0, sizeof(*state));
if (samplerate < 24000) {
PDEBUG(DDSP, DEBUG_ERROR, "Sample rate must be at least 24000 Hz!\n");
return -1;
}
factor = 0.97;
state->p.factor = factor;
state->p.amp = samplerate / 6350.0;
state->d.factor = factor;
state->d.amp = 1.0 / (samplerate / 6350.0);
return 0;
}
void pre_emphasis(emphasis_t *state, int16_t *samples, int num)
{
int32_t sample;
double old_value, new_value, last_value, factor, amp;
int i;
last_value = state->p.last_value;
factor = state->p.factor;
amp = state->p.amp;
for (i = 0; i < num; i++) {
old_value = (double)(*samples) / 32768.0;
new_value = old_value - factor * last_value;
last_value = old_value;
sample = (int)(amp * new_value * 32768.0);
if (sample > 32767)
sample = 32767;
else if (sample < -32768)
sample = -32768;
*samples++ = sample;
}
state->p.last_value = last_value;
}
void de_emphasis(emphasis_t *state, int16_t *samples, int num)
{
int32_t sample;
double old_value, new_value, last_value, factor, amp;
int i;
last_value = state->d.last_value;
factor = state->d.factor;
amp = state->d.amp;
for (i = 0; i < num; i++) {
old_value = (double)(*samples) / 32768.0;
new_value = old_value + factor * last_value;
last_value = new_value;
sample = (int)(amp * new_value * 32768.0);
if (sample > 32767)
sample = 32767;
else if (sample < -32768)
sample = -32768;
*samples++ = sample;
}
state->d.last_value = last_value;
}
|