150 lines
2.7 KiB
C
150 lines
2.7 KiB
C
/* $Id$ */
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#include "stdafx.h"
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#include "openttd.h"
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#include "mixer.h"
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struct MixerChannel {
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bool active;
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// pointer to allocated buffer memory
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int8 *memory;
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// current position in memory
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uint32 pos;
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uint32 frac_pos;
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uint32 frac_speed;
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uint32 samples_left;
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// Mixing volume
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uint volume_left;
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uint volume_right;
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uint flags;
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};
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static MixerChannel _channels[8];
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static uint32 _play_rate;
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static void mix_int8_to_int16(MixerChannel *sc, int16 *buffer, uint samples)
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{
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int8 *b;
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uint32 frac_pos;
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uint32 frac_speed;
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uint volume_left;
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uint volume_right;
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if (samples > sc->samples_left) samples = sc->samples_left;
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sc->samples_left -= samples;
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assert(samples > 0);
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b = sc->memory + sc->pos;
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frac_pos = sc->frac_pos;
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frac_speed = sc->frac_speed;
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volume_left = sc->volume_left;
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volume_right = sc->volume_right;
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if (frac_speed == 0x10000) {
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// Special case when frac_speed is 0x10000
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do {
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buffer[0] += *b * volume_left >> 8;
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buffer[1] += *b * volume_right >> 8;
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b++;
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buffer += 2;
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} while (--samples > 0);
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} else {
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do {
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buffer[0] += *b * volume_left >> 8;
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buffer[1] += *b * volume_right >> 8;
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buffer += 2;
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frac_pos += frac_speed;
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b += frac_pos >> 16;
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frac_pos &= 0xffff;
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} while (--samples > 0);
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}
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sc->frac_pos = frac_pos;
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sc->pos = b - sc->memory;
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}
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static void MxCloseChannel(MixerChannel *mc)
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{
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if (mc->flags & MX_AUTOFREE) free(mc->memory);
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mc->active = false;
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mc->memory = NULL;
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}
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void MxMixSamples(void *buffer, uint samples)
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{
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MixerChannel *mc;
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// Clear the buffer
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memset(buffer, 0, sizeof(int16) * 2 * samples);
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// Mix each channel
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for (mc = _channels; mc != endof(_channels); mc++) {
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if (mc->active) {
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mix_int8_to_int16(mc, buffer, samples);
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if (mc->samples_left == 0) MxCloseChannel(mc);
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}
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}
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#if 0
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{
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static FILE *out = NULL;
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if (out == NULL)
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out = fopen("d:\\dump.raw", "wb");
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fwrite(buffer, samples * 4, 1, out);
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}
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#endif
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}
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MixerChannel *MxAllocateChannel(void)
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{
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MixerChannel *mc;
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for (mc = _channels; mc != endof(_channels); mc++)
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if (mc->memory == NULL) {
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mc->active = false;
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return mc;
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}
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return NULL;
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}
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void MxSetChannelRawSrc(MixerChannel *mc, int8 *mem, uint size, uint rate, uint flags)
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{
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mc->memory = mem;
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mc->flags = flags;
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mc->frac_pos = 0;
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mc->pos = 0;
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mc->frac_speed = (rate << 16) / _play_rate;
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// adjust the magnitude to prevent overflow
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while (size & 0xFFFF0000) {
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size >>= 1;
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rate = (rate >> 1) + 1;
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}
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mc->samples_left = size * _play_rate / rate;
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}
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void MxSetChannelVolume(MixerChannel *mc, uint left, uint right)
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{
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mc->volume_left = left;
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mc->volume_right = right;
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}
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void MxActivateChannel(MixerChannel* mc)
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{
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mc->active = true;
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}
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bool MxInitialize(uint rate)
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{
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_play_rate = rate;
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return true;
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}
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