ref: e3aee39a389700ad821a1619f114e226c1bd42d0
dir: /sys/src/games/nes/apu.c/
#include <u.h> #include <libc.h> #include <thread.h> #include <draw.h> #include "../eui.h" #include "dat.h" #include "fns.h" enum { MAXBUF = 2000 }; enum { LEN = 0, ENV = 4, TRILIN = 6, SWEEP = 8, RELOAD = 10, DMCCTR = 11, DMCSHFT = 12, }; u8int apuseq, apuctr[13]; u16int dmcaddr, dmccnt; static int fd; static short sbuf[2*MAXBUF], *sbufp; int targperiod(int i) { int m, p, t; m = mem[0x4001 + i * 4]; p = mem[0x4002 + i * 4]; p |= (mem[0x4003 + i * 4] & 7) << 8; t = p >> (m & 7); if((m & 8) != 0){ if(i == 0 && t != 0) t--; t = p - t; }else t += p; return t; } static void declen(void) { int i, m, p; u8int *a; for(i = 0; i < 4; i++){ m = mem[0x4000 + i * 4]; if(i == 2) m >>= 2; if((m & 0x20) != 0) continue; if(apuctr[LEN + i] != 0) apuctr[LEN + i]--; } for(i = 0, a = apuctr + SWEEP; i < 2; i++, a++){ m = mem[0x4001 + i * 4]; if((m & 0x80) != 0 && (m & 0x07) != 0 && (*a & 7) == 0){ p = targperiod(i); if(p <= 0x7ff){ mem[0x4002 + i * 4] = p; mem[0x4003 + i * 4] = p >> 8; } } if((*a & 0x80) != 0 || (*a & 7) == 0 && (m & 0x80) != 0) *a = (m & 0x70) >> 4; else if(*a != 0) (*a)--; } } static void doenv(void) { int i, m; u8int *a; for(i = 0, a = apuctr + ENV; i < 4; i++, a++){ if(i == 2) continue; m = mem[0x4000 + 4 * i]; if((apuctr[RELOAD] & (1<<i)) != 0){ *a = 0xf0 | m & 0x0f; apuctr[RELOAD] &= ~(1<<i); }else if((*a & 0x0f) == 0){ *a |= m & 0x0f; if((*a & 0xf0) == 0){ if((m & 0x20) != 0) *a |= 0xf0; }else *a -= 0x10; }else (*a)--; } a = apuctr + TRILIN; if((apuctr[RELOAD] & (1<<2)) != 0) *a = mem[0x4008] & 0x7f; else if(*a != 0) (*a)--; if((mem[0x4008] & 0x80) == 0) apuctr[RELOAD] &= ~(1<<2); } void apustep(void) { int mode, len, env; mode = mem[APUFRAME]; if((mode & 0x80) != 0){ if(apuseq >= 4){ env = len = 0; apuseq = 0; }else{ env = 1; len = (apuseq & 1) == 0; apuseq++; } }else{ env = 1; len = (apuseq & 1) != 0; if(apuseq >= 3){ if((mode & 0x40) == 0) irq |= IRQFRAME; apuseq = 0; }else apuseq++; } if(len) declen(); if(env) doenv(); } static int freq(int i) { int f; f = mem[0x4002 + 4 * i]; f |= (mem[0x4003 + 4 * i] & 0x7) << 8; return f; } static int pulse(int i) { static int c[2]; int m, s, f; f = freq(i); if(f < 8 || targperiod(i) > 0x7ff) f = -1; else f = muldiv(16 * (f + 1), RATE, FREQ/12); if(c[i] >= f) c[i] = 0; else c[i]++; m = mem[0x4000 + 4 * i]; if((m & 0x10) != 0) s = m & 0x0f; else s = apuctr[ENV + i] >> 4; if(c[i] >= f/2 || apuctr[LEN + i] == 0) s = 0; return s; } static int tri(void) { static int c; int f, i; f = freq(2); if(f <= 2) return 7; f = muldiv(32 * (f + 1), RATE, FREQ / 12); if(c >= f) c = 0; else c++; i = 32 * c / f; i ^= (i < 16) ? 0xf : 0x10; if(apuctr[LEN + 2] == 0 || (apuctr[TRILIN] & 0x7f) == 0) return 0; return i; } static int noise(void) { static int c, r=1; int m, f; static int per[] = { 0x004, 0x008, 0x010, 0x020, 0x040, 0x060, 0x080, 0x0A0, 0x0CA, 0x0FE, 0x17C, 0x1FC, 0x2FA, 0x3F8, 0x7F2, 0xFE4, }; m = mem[0x400E]; f = muldiv(per[m & 0x0f], RATE * 1000, FREQ/24); c += 1000; while(c >= f){ r |= ((r ^ (r >> ((m & 0x80) != 0 ? 6 : 1))) & 1) << 15; r >>= 1; c -= f; } if(apuctr[LEN + 3] == 0 || (r & 1) != 0) return 0; m = mem[0x400C]; if((m & 0x10) != 0) return m & 0xf; return apuctr[ENV + 3] >> 4; } static int dmc(void) { return mem[DMCBUF]; } void audiosample(void) { double d; if(sbufp == nil) return; d = 95.88 / (8128.0 / (0.01 + pulse(0) + pulse(1)) + 100); d += 159.79 / (1.0 / (0.01 + tri()/8227.0 + noise()/12241.0 + dmc()/22638.0) + 100.0); if(sbufp < sbuf + nelem(sbuf) - 1){ *sbufp++ = d * 10000; *sbufp++ = d * 10000; } } void dmcstep(void) { if((apuctr[DMCCTR] & 7) == 0){ apuctr[DMCCTR] = 8; if(dmccnt != 0){ apuctr[DMCSHFT] = memread(dmcaddr); if(dmcaddr == 0xFFFF) dmcaddr = 0x8000; else dmcaddr++; if(--dmccnt == 0){ if((mem[DMCCTRL] & 0x40) != 0){ dmcaddr = mem[DMCADDR] * 0x40 + 0xC000; dmccnt = mem[DMCLEN] * 0x10 + 1; }else if((mem[DMCCTRL] & 0x80) != 0) irq |= IRQDMC; } }else apuctr[DMCCTR] |= 0x80; } if((apuctr[DMCCTR] & 0x80) == 0){ if((apuctr[DMCSHFT] & 1) != 0){ if(mem[DMCBUF] < 126) mem[DMCBUF] += 2; }else{ if(mem[DMCBUF] > 1) mem[DMCBUF] -= 2; } } apuctr[DMCSHFT] >>= 1; apuctr[DMCCTR]--; } int audioout(void) { int rc; if(sbufp == nil) return -1; if(sbufp == sbuf) return 0; rc = warp10 ? (sbufp - sbuf) * 2 : write(fd, sbuf, (sbufp - sbuf) * 2); if(rc > 0) sbufp -= (rc+1)/2; if(sbufp < sbuf) sbufp = sbuf; return 0; } void initaudio(void) { fd = open("/dev/audio", OWRITE); if(fd < 0) return; sbufp = sbuf; } u8int apulen[32] = { 0x0A, 0xFE, 0x14, 0x02, 0x28, 0x04, 0x50, 0x06, 0xA0, 0x08, 0x3C, 0x0A, 0x0E, 0x0C, 0x1A, 0x0E, 0x0C, 0x10, 0x18, 0x12, 0x30, 0x14, 0x60, 0x16, 0xC0, 0x18, 0x48, 0x1A, 0x10, 0x1C, 0x20, 0x1E, }; u16int dmclen[16] = { 0x1AC, 0x17C, 0x154, 0x140, 0x11E, 0x0FE, 0x0E2, 0x0D6, 0x0BE, 0x0A0, 0x08E, 0x080, 0x06A, 0x054, 0x048, 0x036, };