tron@2186: /* $Id$ */
tron@2186: 
truelight@0: #include "stdafx.h"
Darkvater@1891: #include "openttd.h"
tron@1496: #include "mixer.h"
truelight@0: 
tron@1496: struct MixerChannel {
truelight@0: 	bool active;
truelight@0: 
truelight@0: 	// pointer to allocated buffer memory
tron@337: 	int8 *memory;
truelight@0: 
truelight@0: 	// 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: 
truelight@0: 	// Mixing volume
truelight@0: 	uint volume_left;
truelight@0: 	uint 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: 
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;
truelight@0: 	uint volume_left;
truelight@0: 	uint 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) {
truelight@0: 		// Special case when frac_speed is 0x10000
truelight@0: 		do {
tron@337: 			buffer[0] += *b * volume_left >> 8;
tron@337: 			buffer[1] += *b * volume_right >> 8;
truelight@0: 			b++;
truelight@0: 			buffer += 2;
tron@337: 		} while (--samples > 0);
truelight@0: 	} else {
truelight@0: 		do {
truelight@0: 			buffer[0] += *b * volume_left >> 8;
truelight@0: 			buffer[1] += *b * volume_right >> 8;
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: 
truelight@0: 	// Clear the buffer
tron@337: 	memset(buffer, 0, sizeof(int16) * 2 * samples);
truelight@193: 
truelight@0: 	// Mix each channel
tron@2977: 	for (mc = _channels; mc != endof(_channels); mc++) {
truelight@0: 		if (mc->active) {
tron@337: 			mix_int8_to_int16(mc, buffer, samples);
tron@337: 			if (mc->samples_left == 0) MxCloseChannel(mc);
truelight@0: 		}
truelight@0: 	}
truelight@0: }
truelight@0: 
tron@2977: MixerChannel *MxAllocateChannel(void)
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: 
tron@1496: void MxSetChannelRawSrc(MixerChannel *mc, int8 *mem, uint 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: 
truelight@0: 	// adjust the magnitude to prevent overflow
tron@337: 	while (size & 0xFFFF0000) {
tron@337: 		size >>= 1;
tron@337: 		rate = (rate >> 1) + 1;
tron@337: 	}
truelight@193: 
tron@2977: 	mc->samples_left = 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: }