ref: cd747191012d0420ac631340d962da1f80cef0a5
dir: /sys/src/games/gb/apu.c/
#include <u.h>
#include <libc.h>
#include <thread.h>
#include "dat.h"
#include "fns.h"
double TAU = 25000;
Event evsamp;
extern Event evenv;
s16int sbuf[2*4000], *sbufp;
enum {
Freq = 44100,
SRATEDIV = FREQ / Freq
};
static int fd;
u16int envmod;
u8int sweepen, sweepcalc, sweepctr;
u16int sweepfreq;
typedef struct chan chan;
struct chan {
u8int *env, *freq;
int per;
u16int len;
u8int n, ectr;
u8int vol, ctr, samp;
};
u8int wpos;
u16int lfsr;
u8int apustatus;
ulong waveclock;
u8int wavebuf;
double samp[2];
chan sndch[4] = {
{
.n = 0,
.env = reg + NR12,
.freq = reg + NR14,
.per = 8 * 2048,
},
{
.n = 1,
.env = reg + NR22,
.freq = reg + NR24,
.per = 8 * 2048,
},
{
.n = 2,
},
{
.n = 3,
.env = reg + NR42,
.freq = reg + NR44,
.per = 32
}
};
Event chev[4] = {
{.aux = &sndch[0]},
{.aux = &sndch[1]},
{.aux = &sndch[2]},
{.aux = &sndch[3]}
};
Var apuvars[] = {
VAR(apustatus), VAR(envmod), VAR(sweepen), VAR(sweepcalc),
VAR(sweepctr), VAR(sweepfreq), VAR(wpos), VAR(lfsr), VAR(waveclock), VAR(wavebuf),
VAR(sndch[0].ectr), VAR(sndch[0].len), VAR(sndch[0].per), VAR(sndch[0].ctr), VAR(sndch[0].vol), VAR(sndch[0].samp),
VAR(sndch[1].ectr), VAR(sndch[1].len), VAR(sndch[1].per), VAR(sndch[1].ctr), VAR(sndch[1].vol), VAR(sndch[1].samp),
VAR(sndch[2].ectr), VAR(sndch[2].len), VAR(sndch[2].per), VAR(sndch[2].vol), VAR(sndch[2].samp),
VAR(sndch[3].ectr), VAR(sndch[3].len), VAR(sndch[3].per), VAR(sndch[3].vol), VAR(sndch[3].samp),
{nil, 0, 0},
};
static void
rate(chan *c, u16int v)
{
switch(c->n){
case 0: case 1:
c->per = 8 * (2048 - (v & 0x7ff));
break;
case 2:
c->per = 4 * (2048 - (v & 0x7ff));
break;
case 3:
c->per = 32;
if((v & 7) != 0)
c->per *= v & 7;
else
c->per >>= 1;
c->per <<= (v >> 4 & 15);
}
}
static void
filter(int t)
{
static int ov0, ov1;
static u32int oclock;
double e;
u8int cntl, cnth;
int i, v;
e = exp((clock + t - oclock) * -(TAU / FREQ));
samp[0] = e * samp[0] + (1 - e) * ov0;
samp[1] = e * samp[1] + (1 - e) * ov1;
oclock = clock + t;
cntl = reg[NR50];
cnth = reg[NR51];
ov0 = 0;
ov1 = 0;
for(i = 0; i < 4; i++){
if(i == 2 ? ((reg[NR30] & 0x80) == 0) : ((*sndch[i].env & 0xf8) == 0))
continue;
v = sndch[i].samp * 2 - 15;
if((cnth & 1<<i) != 0)
ov0 += v;
if((cnth & 1<<4<<i) != 0)
ov1 += v;
}
ov0 *= 1 + (cntl & 7);
ov1 *= 1 + (cntl >> 4 & 7);
}
static void
chansamp(chan *c, int t)
{
u8int ov;
ov = c->samp;
switch(c->n){
case 0: case 1:
c->samp = c->vol;
switch(reg[NR21] >> 6){
case 0: if(c->ctr < 7) c->samp = 0; break;
case 1: if(c->ctr < 6) c->samp = 0; break;
case 2: if(c->ctr < 4) c->samp = 0; break;
case 3: if(c->ctr >= 6) c->samp = 0; break;
}
break;
case 2:
if((apustatus & 1<<4) == 0){
c->samp = 0;
break;
}
c->samp = wavebuf;
if((wpos & 1) == 0)
c->samp >>= 4;
else
c->samp &= 0xf;
if((reg[NR32] & 3<<5) == 0)
c->samp = 0;
else
c->samp = c->samp >> (reg[NR32] >> 5 & 3) - 1;
break;
case 3:
c->samp = (lfsr & 1) != 0 ? 0 : c->vol;
}
if(ov != c->samp)
filter(t);
}
void
chantick(void *vc)
{
chan *c;
u16int l;
c = vc;
switch(c->n){
case 0: case 1:
c->ctr = c->ctr - 1 & 7;
break;
case 2:
wpos = wpos + 1 & 31;
wavebuf = reg[WAVE + (wpos >> 1)];
waveclock = clock;
break;
case 3:
l = lfsr;
lfsr >>= 1;
if(((l ^ lfsr) & 1) != 0)
if((reg[NR43] & 1<<3) != 0)
lfsr |= 0x40;
else
lfsr |= 0x4000;
break;
}
chansamp(c, chev[c->n].time);
addevent(&chev[c->n], c->per);
}
static void
env(chan *c, int t)
{
if((envmod & 1) == 0 && c->len > 0 && (*c->freq & 1<<6) != 0)
if(--c->len == 0){
apustatus &= ~(1<<c->n);
c->vol = 0;
chansamp(c, t);
return;
}
if((apustatus & 1<<c->n) == 0 || (envmod & 7) != 7 || c->ectr == 0 || --c->ectr != 0)
return;
c->ectr = *c->env & 7;
if((*c->env & 1<<3) != 0){
if(c->vol < 15){
c->vol++;
chansamp(c, t);
}
}else
if(c->vol > 0){
c->vol--;
chansamp(c, t);
}
}
static void
sweep(int wb, int t)
{
u16int fr;
int d;
u16int cnt;
cnt = reg[NR10];
d = sweepfreq >> (cnt & 7);
if((cnt & 1<<3) != 0)
d = -d;
fr = sweepfreq + d;
sweepcalc |= cnt;
if(fr > 2047){
sndch[0].len = 0;
sndch[0].vol = 0;
chansamp(&sndch[0], t);
apustatus &= ~1;
sweepen = 0;
}else if(wb && (cnt & 7) != 0){
sweepfreq = fr;
reg[NR13] = fr;
reg[NR14] = reg[NR14] & 0xf8 | fr >> 8;
rate(&sndch[0], fr);
sweep(0, t);
}
}
void
sndstart(chan *c, u8int v)
{
u8int cnt;
filter(0);
c->vol = *c->env >> 4;
c->ectr = *c->env & 7;
if(c->len == 0)
c->len = 64;
apustatus |= 1<<c->n;
if(c == sndch){
cnt = reg[NR10];
sweepen = (cnt & 0x07) != 0 || (cnt & 0x70) != 0;
sweepctr = cnt >> 4 & 7;
sweepctr += sweepctr - 1 & 8;
sweepfreq = v << 8 & 0x700 | reg[NR13];
sweepcalc = 0;
if((cnt & 0x07) != 0)
sweep(0, 0);
}
if((*c->freq & 0x40) == 0 && (v & 0x40) != 0 && (envmod & 1) != 0 && --c->len == 0 || (*c->env & 0xf8) == 0){
apustatus &= ~(1<<c->n);
c->vol = 0;
}
chansamp(c, 0);
}
void
envtick(void *)
{
env(&sndch[0], evenv.time);
env(&sndch[1], evenv.time);
if((envmod & 1) == 0 && sndch[2].len > 0 && (reg[NR34] & 0x40) != 0)
if(--sndch[2].len == 0){
apustatus &= ~4;
delevent(&chev[2]);
}
env(&sndch[3], evenv.time);
if((envmod & 3) == 2 && sweepen && --sweepctr == 0){
sweepctr = reg[NR10] >> 4 & 7;
sweepctr += sweepctr - 1 & 8;
if((reg[NR10] & 0x70) != 0)
sweep(1, evenv.time);
}
envmod++;
addevent(&evenv, FREQ / 512);
}
void
sampletick(void *)
{
filter(evsamp.time);
if(sbufp < sbuf + nelem(sbuf)){
sbufp[0] = samp[0] * 30;
sbufp[1] = samp[1] * 30;
sbufp += 2;
}
addevent(&evsamp, SRATEDIV);
}
void
sndwrite(u8int a, u8int v)
{
static u16int thr[4] = {0x2000, 0x4000, 0x8000, 0xC000};
static u8int clrreg[] = {
0x80, 0x3f, 0x00, 0xff, 0xbf,
0xff, 0x3f, 0x00, 0xff, 0xbf,
0x7f, 0xff, 0x9f, 0xff, 0xbf,
0xff, 0xff, 0x00, 0x00, 0xbf,
0x00, 0x00
};
if((reg[NR52] & 0x80) == 0 && a != NR52 && ((mode & CGB) != 0 || a != NR11 && a != NR21 && a != NR31 && a != NR41))
return;
switch(a){
case NR10:
if((sweepcalc & 0x08) != 0 && (reg[NR10] & ~v & 0x08) != 0){
sndch[0].vol = 0;
apustatus &= ~1;
sweepcalc = 0;
}
break;
case NR11:
sndch[0].len = 64 - (v & 63);
break;
case NR12:
if((v & 0xf8) == 0){
sndch[0].vol = 0;
apustatus &= ~1;
}
break;
case NR13:
rate(&sndch[0], reg[NR14] << 8 & 0x700 | v);
break;
case NR14:
rate(&sndch[0], v << 8 & 0x700 | reg[NR13]);
if((v & 1<<7) != 0)
sndstart(&sndch[0], v);
break;
case NR21:
sndch[1].len = 64 - (v & 63);
break;
case NR22:
if((v & 0xf8) == 0){
sndch[1].vol = 0;
apustatus &= ~2;
}
break;
case NR23:
rate(&sndch[1], reg[NR24] << 8 & 0x700 | v);
break;
case NR24:
rate(&sndch[1], v << 8 & 0x700 | reg[NR23]);
if((v & 1<<7) != 0)
sndstart(&sndch[1], v);
break;
case NR30:
if((v & 0x80) == 0){
apustatus &= ~4;
delevent(&chev[2]);
}
break;
case NR31:
sndch[2].len = 256 - (v & 0xff);
break;
case NR33:
rate(&sndch[2], reg[NR34] << 8 & 0x700 | v);
break;
case NR34:
rate(&sndch[2], v << 8 & 0x700 | reg[NR33]);
if((v & 0x80) != 0){
if(sndch[2].len == 0)
sndch[2].len = 256;
wpos = 0;
if((reg[NR30] & 0x80) != 0){
apustatus |= 4;
delevent(&chev[2]);
addevent(&chev[2], sndch[2].per);
}
}
break;
case NR41:
sndch[3].len = 64 - (v & 63);
break;
case NR42:
if((v & 0xf8) == 0){
sndch[3].vol = 0;
apustatus &= ~8;
}
break;
case NR43:
rate(&sndch[3], v);
break;
case NR44:
if((v & 1<<7) != 0){
if((reg[NR43] & 1<<3) != 0)
lfsr = 0x7f;
else
lfsr = 0x7fff;
sndstart(&sndch[3], v);
}
break;
case NR50: case NR51:
filter(0);
break;
case NR52:
apustatus = v & 0xf0 | apustatus & 0x0f;
if((v & 0x80) == 0){
memcpy(reg + NR10, clrreg, NR52 - NR10);
if((mode & CGB) != 0){
sndch[0].len = 0;
sndch[1].len = 0;
sndch[2].len = 0;
sndch[3].len = 0;
apustatus = 0;
delevent(&chev[2]);
}
}else if((reg[NR52] & 0x80) == 0){
envmod = 0;
delevent(&evenv);
addevent(&evenv, FREQ / 512);
sndch[0].ctr = 0;
sndch[1].ctr = 0;
}
}
reg[a] = v;
}
u8int
waveread(u8int a)
{
if((apustatus & 4) != 0)
if((mode & CGB) != 0 || clock - waveclock == 0)
return wavebuf;
else
return 0xff;
return reg[WAVE + a];
}
void
wavewrite(u8int a, u8int v)
{
reg[WAVE + a] = v;
}
void
audioinit(void)
{
fd = open("/dev/audio", OWRITE);
if(fd < 0)
sysfatal("open: %r");
sbufp = sbuf;
evsamp.f = sampletick;
addevent(&evsamp, SRATEDIV);
addevent(&chev[0], 8 * 2048);
addevent(&chev[1], 8 * 2048);
addevent(&chev[3], 8 * 2048);
}
int
audioout(void)
{
int rc;
static int cl;
if(sbufp == nil)
return -1;
if(sbufp == sbuf)
return 0;
cl = clock;
rc = write(fd, sbuf, (sbufp - sbuf) * 2);
if(rc > 0)
sbufp -= (rc+1)/2;
if(sbufp < sbuf)
sbufp = sbuf;
return 0;
}