ref: a2be120ea93ae67447315da268fa336650cd5149
dir: /sys/src/games/nes/apu.c/
#include <u.h>
#include <libc.h>
#include <thread.h>
#include <draw.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 = 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,
};