mixer.c
author bjarni
Fri, 08 Sep 2006 10:47:39 +0000
changeset 4574 497540b4a75f
parent 2977 0240dd4704a7
child 5120 e12dfc67761f
permissions -rw-r--r--
(svn r6424) -Codechange: [autoreplace] removed a loop though all vehicles from each time the window is redrawn
To do this, the player struct contains an array, that contains the count of each engine type that the player owns
Those arrays are updated each time a vehicle is build or deleted and is calculated on load (it's not saved)
It's possible to access the arrays outside of the autoreplace GUI, so feel free to read from them in other patches as well
/* $Id$ */

#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);
		}
	}

	#if 0
	{
		static FILE *out = NULL;
		if (out == NULL)
			out = fopen("d:\\dump.raw", "wb");
		fwrite(buffer, samples * 4, 1, out);
	}
	#endif
}

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;
}