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@ r7939:523d421f9d0c
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Location: cpp/openttd-patchpack/source/src/mixer.cpp
r7939:523d421f9d0c
2.6 KiB
text/x-c
(svn r11492) -Codechange: [OSX] Split the cocoa video driver into several files. The reason for this is that the fullscreen and windowed mode api are separate from each other in OS X and thus the driver actual is two drivers in one. This split is to make the code more readable and to prepare for replacing the Quickdraw windowed mode code which uses apis deprecated as of OS X 10.5 (and maybe earlier).
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/** @file mixer.cpp*/
#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, (int16*)buffer, samples);
if (mc->samples_left == 0) MxCloseChannel(mc);
}
}
}
MixerChannel *MxAllocateChannel()
{
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;
}
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