106 lines
2.1 KiB
C
106 lines
2.1 KiB
C
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#include <inttypes.h>
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#include "synth.h"
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#include "freq_table.h"
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synth_instrument_t instruments[256];
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uint8_t wave_table[256][2];
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uint8_t patterns[256][pattern_length][2];
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uint8_t pattern_table[256][channel_count];
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uint8_t tune_length;
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int16_t sample;
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int8_t tick;
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int8_t row;
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int8_t seq;
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static synth_channel_t channels[channel_count];
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uint16_t synth_mix(void)
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{
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if(sample == 0) { // new tick
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for(int i = 0; i < channel_count; i++) {
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synth_channel_t* chan = &channels[i];
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const synth_instrument_t* inst = &instruments[chan->inst_nr];
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if(chan->level > inst->decay) chan->level -= inst->decay;
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else chan->level = 0;
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chan->pulse_width += inst->pulse_sweep;
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chan->pos++;
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if(wave_table[chan->pos][1] == 0xff) chan->pos += wave_table[chan->pos][0];
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// enter new row
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if(tick == 0) {
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uint8_t pattern_nr = pattern_table[seq][i];
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uint8_t note = patterns[pattern_nr][row][0];
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if(note) { // new note, maybe?
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if(note == 0xff) {
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chan->level = 0;
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} else {
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chan->level = 80; // TODO: less?
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chan->note = note;
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chan->inst_nr = patterns[pattern_nr][row][1];
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inst = &instruments[chan->inst_nr];
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chan->pos = inst->wave_table_pos;
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if(inst->pulse_width) chan->pulse_width = inst->pulse_width;
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}
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}
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}
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}
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}
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if(++sample == tick_length) {
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sample = 0;
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if(++tick == row_length) {
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tick = 0;
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if(++row == pattern_length) {
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row = 0;
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if(++seq == tune_length) {
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seq = 0;
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}
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}
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}
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}
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uint16_t output = 0;
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for(int i = 0; i < channel_count; i++) {
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synth_channel_t* chan = &channels[i];
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const synth_instrument_t* inst = &instruments[chan->inst_nr];
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chan->phase += freq_table[(uint8_t)(chan->note + wave_table[chan->pos][0])];
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uint8_t amp;
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switch(wave_table[chan->pos][1]) {
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case WAVE_PULSE:
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amp = -(chan->phase < chan->pulse_width);
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break;
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case WAVE_SAW:
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amp = (chan->phase >> 8);
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break;
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case WAVE_NOISE: // shitty noise
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chan->phase = (chan->phase >> 1) ^ (-(chan->phase & 1) & 0xb400);
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amp = (chan->phase >> 8);
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break;
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default:
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amp = 0;
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break;
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}
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output += ((amp & 0xff) * chan->level) >> 8;
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}
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return output;
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}
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