tron@2186: /* $Id$ */
tron@2186: 
rubidium@10429: /** @file mixer.cpp Mixing of sound samples. */
belugas@6527: 
truelight@0: #include "stdafx.h"
Darkvater@1891: #include "openttd.h"
tron@1496: #include "mixer.h"
rubidium@11137: #include "core/math_func.hpp"
truelight@0: 
tron@1496: struct MixerChannel {
truelight@0: 	bool active;
truelight@0: 
belugas@6527: 	/* pointer to allocated buffer memory */
tron@337: 	int8 *memory;
truelight@0: 
belugas@6527: 	/* current position in memory */
truelight@0: 	uint32 pos;
truelight@0: 	uint32 frac_pos;
truelight@0: 	uint32 frac_speed;
truelight@0: 	uint32 samples_left;
truelight@0: 
belugas@6527: 	/* Mixing volume */
rubidium@11137: 	int volume_left;
rubidium@11137: 	int volume_right;
truelight@0: 
truelight@0: 	uint flags;
tron@1496: };
truelight@0: 
tron@2977: static MixerChannel _channels[8];
tron@2977: static uint32 _play_rate;
truelight@0: 
rubidium@11137: /**
rubidium@11137:  * The theoretical maximum volume for a single sound sample. Multiple sound
rubidium@11137:  * samples should not exceed this limit as it will sound too loud. It also
rubidium@11137:  * stops overflowing when too many sounds are played at the same time, which
rubidium@11137:  * causes an even worse sound quality.
rubidium@11137:  */
rubidium@11137: static const int MAX_VOLUME = 128 * 128;
rubidium@11137: 
truelight@0: 
truelight@0: static void mix_int8_to_int16(MixerChannel *sc, int16 *buffer, uint samples)
truelight@0: {
truelight@0: 	int8 *b;
truelight@0: 	uint32 frac_pos;
truelight@0: 	uint32 frac_speed;
rubidium@11137: 	int volume_left;
rubidium@11137: 	int volume_right;
truelight@0: 
truelight@0: 	if (samples > sc->samples_left) samples = sc->samples_left;
truelight@0: 	sc->samples_left -= samples;
truelight@0: 	assert(samples > 0);
truelight@0: 
tron@337: 	b = sc->memory + sc->pos;
truelight@0: 	frac_pos = sc->frac_pos;
truelight@0: 	frac_speed = sc->frac_speed;
truelight@0: 	volume_left = sc->volume_left;
truelight@0: 	volume_right = sc->volume_right;
truelight@0: 
truelight@193: 	if (frac_speed == 0x10000) {
belugas@6527: 		/* Special case when frac_speed is 0x10000 */
truelight@0: 		do {
rubidium@11137: 			buffer[0] = Clamp(buffer[0] + (*b * volume_left  >> 8), -MAX_VOLUME, MAX_VOLUME);
frosch@11148: 			buffer[1] = Clamp(buffer[1] + (*b * volume_right >> 8), -MAX_VOLUME, MAX_VOLUME);
truelight@0: 			b++;
truelight@0: 			buffer += 2;
tron@337: 		} while (--samples > 0);
truelight@0: 	} else {
truelight@0: 		do {
rubidium@11137: 			buffer[0] = Clamp(buffer[0] + (*b * volume_left  >> 8), -MAX_VOLUME, MAX_VOLUME);
frosch@11148: 			buffer[1] = Clamp(buffer[1] + (*b * volume_right >> 8), -MAX_VOLUME, MAX_VOLUME);
truelight@0: 			buffer += 2;
truelight@0: 			frac_pos += frac_speed;
truelight@0: 			b += frac_pos >> 16;
truelight@0: 			frac_pos &= 0xffff;
tron@337: 		} while (--samples > 0);
truelight@0: 	}
truelight@0: 
truelight@0: 	sc->frac_pos = frac_pos;
tron@337: 	sc->pos = b - sc->memory;
truelight@0: }
truelight@0: 
truelight@0: static void MxCloseChannel(MixerChannel *mc)
truelight@0: {
tron@337: 	if (mc->flags & MX_AUTOFREE) free(mc->memory);
tron@1497: 	mc->active = false;
truelight@0: 	mc->memory = NULL;
truelight@0: }
truelight@0: 
tron@2977: void MxMixSamples(void *buffer, uint samples)
truelight@0: {
truelight@0: 	MixerChannel *mc;
truelight@193: 
belugas@6527: 	/* Clear the buffer */
tron@337: 	memset(buffer, 0, sizeof(int16) * 2 * samples);
truelight@193: 
belugas@6527: 	/* Mix each channel */
tron@2977: 	for (mc = _channels; mc != endof(_channels); mc++) {
truelight@0: 		if (mc->active) {
rubidium@5838: 			mix_int8_to_int16(mc, (int16*)buffer, samples);
tron@337: 			if (mc->samples_left == 0) MxCloseChannel(mc);
truelight@0: 		}
truelight@0: 	}
truelight@0: }
truelight@0: 
rubidium@6573: MixerChannel *MxAllocateChannel()
truelight@0: {
truelight@0: 	MixerChannel *mc;
tron@2977: 	for (mc = _channels; mc != endof(_channels); mc++)
tron@337: 		if (mc->memory == NULL) {
truelight@0: 			mc->active = false;
truelight@0: 			return mc;
truelight@0: 		}
truelight@0: 	return NULL;
truelight@0: }
truelight@0: 
rubidium@10751: void MxSetChannelRawSrc(MixerChannel *mc, int8 *mem, size_t size, uint rate, uint flags)
truelight@0: {
truelight@0: 	mc->memory = mem;
truelight@0: 	mc->flags = flags;
truelight@0: 	mc->frac_pos = 0;
truelight@0: 	mc->pos = 0;
truelight@0: 
tron@2977: 	mc->frac_speed = (rate << 16) / _play_rate;
truelight@0: 
belugas@6527: 	/* adjust the magnitude to prevent overflow */
rubidium@10751: 	while (size & ~0xFFFF) {
tron@337: 		size >>= 1;
tron@337: 		rate = (rate >> 1) + 1;
tron@337: 	}
truelight@193: 
rubidium@10751: 	mc->samples_left = (uint)size * _play_rate / rate;
truelight@0: }
truelight@0: 
tron@1496: void MxSetChannelVolume(MixerChannel *mc, uint left, uint right)
truelight@0: {
truelight@0: 	mc->volume_left = left;
truelight@0: 	mc->volume_right = right;
truelight@0: }
truelight@0: 
tron@337: 
tron@1498: void MxActivateChannel(MixerChannel* mc)
tron@1496: {
tron@1496: 	mc->active = true;
truelight@0: }
truelight@0: 
truelight@193: 
tron@1496: bool MxInitialize(uint rate)
truelight@0: {
tron@2977: 	_play_rate = rate;
truelight@0: 	return true;
truelight@0: }