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
|
/* $Id$ */
#include "stdafx.h"
#include "openttd.h"
#include "mixer.h"
struct MixerChannel {
bool active;
// pointer to allocated buffer memory
int8 *memory;
// current position in memory
uint32 pos;
uint32 frac_pos;
uint32 frac_speed;
uint32 samples_left;
// Mixing volume
uint volume_left;
uint volume_right;
uint flags;
};
static MixerChannel _channels[8];
static uint32 _play_rate;
static void mix_int8_to_int16(MixerChannel *sc, int16 *buffer, uint samples)
{
int8 *b;
uint32 frac_pos;
uint32 frac_speed;
uint volume_left;
uint volume_right;
if (samples > sc->samples_left) samples = sc->samples_left;
sc->samples_left -= samples;
assert(samples > 0);
b = sc->memory + sc->pos;
frac_pos = sc->frac_pos;
frac_speed = sc->frac_speed;
volume_left = sc->volume_left;
volume_right = sc->volume_right;
if (frac_speed == 0x10000) {
// Special case when frac_speed is 0x10000
do {
buffer[0] += *b * volume_left >> 8;
buffer[1] += *b * volume_right >> 8;
b++;
buffer += 2;
} while (--samples > 0);
} else {
do {
buffer[0] += *b * volume_left >> 8;
buffer[1] += *b * volume_right >> 8;
buffer += 2;
frac_pos += frac_speed;
b += frac_pos >> 16;
frac_pos &= 0xffff;
} while (--samples > 0);
}
sc->frac_pos = frac_pos;
sc->pos = b - sc->memory;
}
static void MxCloseChannel(MixerChannel *mc)
{
if (mc->flags & MX_AUTOFREE) free(mc->memory);
mc->active = false;
mc->memory = NULL;
}
void MxMixSamples(void *buffer, uint samples)
{
MixerChannel *mc;
// Clear the buffer
memset(buffer, 0, sizeof(int16) * 2 * samples);
// Mix each channel
for (mc = _channels; mc != endof(_channels); mc++) {
if (mc->active) {
mix_int8_to_int16(mc, buffer, samples);
if (mc->samples_left == 0) MxCloseChannel(mc);
}
}
}
MixerChannel *MxAllocateChannel(void)
{
MixerChannel *mc;
for (mc = _channels; mc != endof(_channels); mc++)
if (mc->memory == NULL) {
mc->active = false;
return mc;
}
return NULL;
}
void MxSetChannelRawSrc(MixerChannel *mc, int8 *mem, uint size, uint rate, uint flags)
{
mc->memory = mem;
mc->flags = flags;
mc->frac_pos = 0;
mc->pos = 0;
mc->frac_speed = (rate << 16) / _play_rate;
// adjust the magnitude to prevent overflow
while (size & 0xFFFF0000) {
size >>= 1;
rate = (rate >> 1) + 1;
}
mc->samples_left = size * _play_rate / rate;
}
void MxSetChannelVolume(MixerChannel *mc, uint left, uint right)
{
mc->volume_left = left;
mc->volume_right = right;
}
void MxActivateChannel(MixerChannel* mc)
{
mc->active = true;
}
bool MxInitialize(uint rate)
{
_play_rate = rate;
return true;
}
|
