98 lines
2.3 KiB
C
98 lines
2.3 KiB
C
#include "../uxn.h"
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#include "apu.h"
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/*
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Copyright (c) 2021 Devine Lu Linvega
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Copyright (c) 2021 Andrew Alderwick
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Permission to use, copy, modify, and distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE.
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*/
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#define NOTE_PERIOD (SAMPLE_FREQUENCY * 0x4000 / 11025)
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#define ADSR_STEP (SAMPLE_FREQUENCY / 0xf)
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/* clang-format off */
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static Uint32 advances[12] = {
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0x80000, 0x879c8, 0x8facd, 0x9837f, 0xa1451, 0xaadc1,
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0xb504f, 0xbfc88, 0xcb2ff, 0xd7450, 0xe411f, 0xf1a1c
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};
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/* clang-format on */
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static Sint32
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envelope(Apu *c, Uint32 age)
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{
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if(!c->r) return 0x0888;
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if(age < c->a) return 0x0888 * age / c->a;
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if(age < c->d) return 0x0444 * (2 * c->d - c->a - age) / (c->d - c->a);
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if(age < c->s) return 0x0444;
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if(age < c->r) return 0x0444 * (c->r - age) / (c->r - c->s);
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c->advance = 0;
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return 0x0000;
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}
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int
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apu_render(Apu *c, Sint16 *sample, Sint16 *end)
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{
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Sint32 s;
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if(!c->advance || !c->period) return 0;
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while(sample < end) {
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c->count += c->advance;
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c->i += c->count / c->period;
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c->count %= c->period;
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if(c->i >= c->len) {
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if(!c->repeat) {
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c->advance = 0;
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break;
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}
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c->i %= c->len;
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}
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s = (Sint8)(c->addr[c->i] + 0x80) * envelope(c, c->age++);
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*sample++ += s * c->volume[0] / 0x180;
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*sample++ += s * c->volume[1] / 0x180;
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}
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if(!c->advance) apu_finished_handler(c);
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return 1;
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}
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void
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apu_start(Apu *c, Uint16 adsr, Uint8 pitch)
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{
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if(pitch < 108 && c->len)
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c->advance = advances[pitch % 12] >> (8 - pitch / 12);
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else {
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c->advance = 0;
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return;
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}
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c->a = ADSR_STEP * (adsr >> 12);
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c->d = ADSR_STEP * (adsr >> 8 & 0xf) + c->a;
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c->s = ADSR_STEP * (adsr >> 4 & 0xf) + c->d;
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c->r = ADSR_STEP * (adsr >> 0 & 0xf) + c->s;
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c->age = 0;
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c->i = 0;
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if(c->len <= 0x100) /* single cycle mode */
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c->period = NOTE_PERIOD * 337 / 2 / c->len;
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else /* sample repeat mode */
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c->period = NOTE_PERIOD;
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}
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Uint8
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apu_get_vu(Apu *c)
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{
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int i;
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Sint32 sum[2] = {0, 0};
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if(!c->advance || !c->period) return 0;
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for(i = 0; i < 2; ++i) {
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if(!c->volume[i]) continue;
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sum[i] = 1 + envelope(c, c->age) * c->volume[i] / 0x800;
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if(sum[i] > 0xf) sum[i] = 0xf;
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}
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return (sum[0] << 4) | sum[1];
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}
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