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
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
/* compress.c
* Compressor logic
*
* (c)2007 busybee (http://beesbuzz.biz/
* Licensed under the terms of the LGPL. See the file COPYING for details.
*/
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "config.h"
#include "compress.h"
struct Compressor {
//! The compressor's preferences
struct CompressorConfig prefs;
//! History of the peak values
int *peaks;
//! History of the gain values
int *gain;
//! History of clip amounts
int *clipped;
unsigned int pos;
unsigned int bufsz;
};
struct Compressor *Compressor_new(unsigned int history)
{
struct Compressor *obj = malloc(sizeof(struct Compressor));
if (obj == NULL)
/* out of memory, not much we can do */
abort();
obj->prefs.target = TARGET;
obj->prefs.maxgain = GAINMAX;
obj->prefs.smooth = GAINSMOOTH;
obj->peaks = obj->gain = obj->clipped = NULL;
obj->bufsz = 0;
obj->pos = 0;
Compressor_setHistory(obj, history);
return obj;
}
void Compressor_delete(struct Compressor *obj)
{
if (obj->peaks)
free(obj->peaks);
if (obj->gain)
free(obj->gain);
if (obj->clipped)
free(obj->clipped);
free(obj);
}
static int *resizeArray(int *data, int newsz, int oldsz)
{
data = realloc(data, newsz*sizeof(int));
if (data == NULL)
/* out of memory, not much we can do */
abort();
if (newsz > oldsz)
memset(data + oldsz, 0, sizeof(int)*(newsz - oldsz));
return data;
}
void Compressor_setHistory(struct Compressor *obj, unsigned int history)
{
if (!history)
history = BUCKETS;
obj->peaks = resizeArray(obj->peaks, history, obj->bufsz);
obj->gain = resizeArray(obj->gain, history, obj->bufsz);
obj->clipped = resizeArray(obj->clipped, history, obj->bufsz);
obj->bufsz = history;
}
struct CompressorConfig *Compressor_getConfig(struct Compressor *obj)
{
return &obj->prefs;
}
void Compressor_Process_int16(struct Compressor *obj, int16_t *audio,
unsigned int count)
{
struct CompressorConfig *prefs = Compressor_getConfig(obj);
int16_t *ap;
unsigned int i;
int *peaks = obj->peaks;
int curGain = obj->gain[obj->pos];
int newGain;
int peakVal = 1;
int peakPos = 0;
int slot = (obj->pos + 1) % obj->bufsz;
int *clipped = obj->clipped + slot;
unsigned int ramp = count;
int delta;
ap = audio;
for (i = 0; i < count; i++)
{
int val = *ap++;
if (val < 0)
val = -val;
if (val > peakVal)
{
peakVal = val;
peakPos = i;
}
}
peaks[slot] = peakVal;
for (i = 0; i < obj->bufsz; i++)
{
if (peaks[i] > peakVal)
{
peakVal = peaks[i];
peakPos = 0;
}
}
//! Determine target gain
newGain = (1 << 10)*prefs->target/peakVal;
//! Adjust the gain with inertia from the previous gain value
newGain = (curGain*((1 << prefs->smooth) - 1) + newGain)
>> prefs->smooth;
//! Make sure it's no more than the maximum gain value
if (newGain > (prefs->maxgain << 10))
newGain = prefs->maxgain << 10;
//! Make sure it's no less than 1:1
if (newGain < (1 << 10))
newGain = 1 << 10;
//! Make sure the adjusted gain won't cause clipping
if ((peakVal*newGain >> 10) > 32767)
{
newGain = (32767 << 10)/peakVal;
//! Truncate the ramp time
ramp = peakPos;
}
//! Record the new gain
obj->gain[slot] = newGain;
if (!ramp)
ramp = 1;
if (!curGain)
curGain = 1 << 10;
delta = (newGain - curGain) / (int)ramp;
ap = audio;
*clipped = 0;
for (i = 0; i < count; i++)
{
int sample;
//! Amplify the sample
sample = *ap*curGain >> 10;
if (sample < -32768)
{
*clipped += -32768 - sample;
sample = -32768;
} else if (sample > 32767)
{
*clipped += sample - 32767;
sample = 32767;
}
*ap++ = sample;
//! Adjust the gain
if (i < ramp)
curGain += delta;
else
curGain = newGain;
}
obj->pos = slot;
}
|
