ref: 51f76ae999813bdbf33b06bb4e6c6c8b00f4aec8
dir: /sys/src/games/gba/apu.c/
#include <u.h>
#include <libc.h>
#include <thread.h>
#include "dat.h"
#include "fns.h"
Event evsamp;
int srate, sratediv;
s16int sbuf[2*4000], *sbufp, bias;
enum {
Freq = 44100,
};
static int stime;
s8int snddma[2];
static int fd;
u16int envctr, envrel, envmod;
u8int sweepen, sweepctr;
u16int sweepfreq;
typedef struct chan chan;
struct chan {
u8int n, ectr;
u16int len;
u16int *env, *freq;
u16int fctr, fthr;
u32int finc;
u8int vol;
};
u8int wave[64], wpos, wbank;
u16int lfsr;
chan sndch[4] = {
{
.n = 0,
.env = reg + 0x62/2,
.freq = reg + 0x64/2,
},
{
.n = 1,
.env = reg + 0x68/2,
.freq = reg + 0x6c/2,
},
{
.n = 2,
},
{
.n = 3,
.env = reg + 0x78/2,
.freq = reg + 0x7c/2,
}
};
Var apuvars[] = {
ARR(snddma), VAR(envctr), VAR(envrel), VAR(envmod), VAR(sweepen),
VAR(sweepctr), VAR(sweepfreq), ARR(wave), VAR(wpos), VAR(wbank), VAR(lfsr),
VAR(sndch[0].ectr), VAR(sndch[0].len), VAR(sndch[0].fctr), VAR(sndch[0].fthr), VAR(sndch[0].finc), VAR(sndch[0].vol),
VAR(sndch[1].ectr), VAR(sndch[1].len), VAR(sndch[1].fctr), VAR(sndch[1].fthr), VAR(sndch[1].finc), VAR(sndch[1].vol),
VAR(sndch[2].ectr), VAR(sndch[2].len), VAR(sndch[2].fctr), VAR(sndch[2].fthr), VAR(sndch[2].finc), VAR(sndch[2].vol),
VAR(sndch[3].ectr), VAR(sndch[3].len), VAR(sndch[3].fctr), VAR(sndch[3].fthr), VAR(sndch[3].finc), VAR(sndch[3].vol),
{nil, 0, 0},
};
void
rate(int i, u16int v)
{
switch(i){
case 0: case 1:
sndch[i].finc = 131072ULL * 65536 / (srate * (2048 - (v & 0x7ff)));
break;
case 2:
sndch[2].finc = 2097152ULL * 65536 / (srate * (2048 - (v & 0x7ff)));
break;
case 3:
sndch[3].finc = 524288ULL * 65536 / srate;
if((v & 7) != 0)
sndch[3].finc /= v & 7;
else
sndch[3].finc <<= 1;
sndch[3].finc >>= (v >> 4 & 15) + 1;
}
}
void
env(chan *c)
{
if((envmod & 1) == 0 && c->len > 0 && (*c->freq & 1<<14) != 0)
--c->len;
if(c->len == 0){
c->vol = 0;
return;
}
if((envmod & 7) != 7 || c->ectr == 0 || --c->ectr != 0)
return;
c->ectr = *c->env >> 8 & 7;
if((*c->env & 1<<11) != 0){
if(c->vol < 15)
c->vol++;
}else
if(c->vol > 0)
c->vol--;
}
s8int
wavesamp(void)
{
s8int x;
u16int vol, cnt;
int v;
sndch[2].fctr = v = sndch[2].fctr + sndch[2].finc;
if(sndch[2].len == 0 || (reg[0x70/2] & 1<<7) == 0)
return 0;
vol = reg[0x72/2];
cnt = reg[0x70/2];
for(;;){
x = wave[wbank ^ wpos];
v -= 0x10000;
if(v < 0)
break;
wpos++;
if((cnt & 1<<5) != 0)
wpos &= 63;
else
wpos &= 31;
}
if((vol & 1<<15) != 0)
x = (x >> 2) + (x >> 3);
else if((vol & 3<<14) == 0)
x = 0;
else
x = x >> (vol >> 14 & 3);
return x;
}
s8int
lfsrsamp(void)
{
int v;
u16int l;
sndch[3].fctr = v = sndch[3].fctr + sndch[3].finc;
for(;;){
l = lfsr;
v -= 0x10000;
if(v < 0)
break;
lfsr >>= 1;
if(((l ^ lfsr) & 1) != 0)
if((reg[0x7c/2] & 1<<3) != 0)
lfsr |= 0x40;
else
lfsr |= 0x4000;
}
if((l & 1) != 0)
return -sndch[3].vol;
else
return sndch[3].vol;
}
void
sweep(int wb)
{
u16int fr;
int d;
u16int cnt;
cnt = reg[0x60/2];
d = sweepfreq >> (cnt & 7);
if((cnt & 1<<3) != 0)
d = -d;
fr = sweepfreq + d;
if(fr > 2047){
sndch[0].len = 0;
sndch[0].vol = 0;
sweepen = 0;
}else if(wb){
sweepfreq = fr;
reg[0x64/2] = reg[0x64/2] & 0xfc00 | fr;
rate(0, fr);
sweep(0);
}
}
void
sndstart(chan *c, u16int v)
{
u16int cnt;
c->vol = *c->env >> 12;
c->ectr = *c->env >> 8 & 7;
if(c->len == 0)
c->len = 64;
if(c == sndch){
cnt = reg[0x60/2];
sweepen = (cnt & 0x07) != 0 && (cnt & 0x70) != 0;
sweepctr = cnt >> 4 & 7;
sweepfreq = v & 0x7ff;
if((cnt & 0x07) != 0)
sweep(0);
}
}
void
sampletick(void *)
{
u16int cntl, cnth;
s16int ch[6];
s16int s[2];
int i;
addevent(&evsamp, sratediv);
if(--envctr == 0){
envctr = envrel;
env(&sndch[0]);
env(&sndch[1]);
if((envmod & 1) == 0 && sndch[2].len > 0 && (reg[0x74/2] & 1<<14) != 0)
sndch[2].len--;
env(&sndch[3]);
if((envmod & 3) == 2 && sweepen && --sweepctr == 0){
sweepctr = reg[0x60/2] >> 4 & 7;
sweep(1);
}
envmod++;
}
sndch[0].fctr += sndch[0].finc;
if(sndch[0].fctr >= sndch[0].fthr)
ch[0] = sndch[0].vol;
else
ch[0] = -sndch[0].vol;
sndch[1].fctr += sndch[1].finc;
if(sndch[1].fctr >= sndch[1].fthr)
ch[1] = sndch[1].vol;
else
ch[1] = -sndch[1].vol;
ch[2] = wavesamp();
ch[3] = lfsrsamp();
cntl = reg[SOUNDCNTL];
cnth = reg[SOUNDCNTH];
for(i = 0; i < 4; i++)
ch[i] = ch[i] >> (cnth & 3);
ch[5] = snddma[0] << 1 + (cnth >> 2 & 1);
ch[6] = snddma[1] << 1 + (cnth >> 3 & 1);
s[0] = 0;
s[1] = 0;
for(i = 0; i < 4; i++){
if((cntl & 1<<8<<i) != 0)
s[1] += ch[i] * (1 + (cntl & 7));
if((cntl & 1<<12<<i) != 0)
s[0] += ch[i] * (1 + (cntl >> 4 & 7));
}
for(i = 5; i < 6; i++){
if((cnth & 1<<3<<i) != 0)
s[1] += ch[i];
if((cnth & 1<<4<<i) != 0)
s[0] += ch[i];
}
s[0] += bias;
s[1] += bias;
if(s[0] < -0x200) s[0] = -0x200;
else if(s[0] > 0x1ff) s[0] = 0x1ff;
if(s[1] < -0x200) s[1] = -0x200;
else if(s[1] > 0x1ff) s[1] = 0x1ff;
stime -= Freq;
while(stime < 0){
if(sbufp < sbuf + nelem(sbuf)){
sbufp[0] = s[0] << 6;
sbufp[1] = s[1] << 6;
sbufp += 2;
}
stime += srate;
}
}
void
sndwrite(u16int a, u16int v)
{
int sh, p, i;
static u16int thr[4] = {0x2000, 0x4000, 0x8000, 0xC000};
switch(a){
case 0x62:
sndch[0].fthr = thr[v >> 6 & 3];
sndch[0].len = 64 - (v & 63);
break;
case 0x64:
rate(0, v);
if((v & 1<<15) != 0)
sndstart(&sndch[0], v);
break;
case 0x68:
sndch[1].fthr = thr[v >> 6 & 3];
break;
case 0x6c:
rate(1, v);
if((v & 1<<15) != 0)
sndstart(&sndch[1], v);
break;
case 0x70:
wbank = v >> 1 & 32;
break;
case 0x72:
sndch[2].len = 256 - (v & 0xff);
break;
case 0x74:
rate(2, v);
if((v & 1<<15) != 0 && sndch[2].len == 0)
sndch[2].len = 256;
break;
case 0x7c:
rate(3, v);
if((v & 1<<15) != 0){
if((v & 1<<3) != 0)
lfsr = 0x7f;
else
lfsr = 0x7fff;
sndstart(&sndch[3], v);
}
break;
case SOUNDBIAS*2:
sh = 9 - (v >> 14 & 3);
if(sratediv != 1<<sh){
srate = 1 << 24 - sh;
sratediv = 1 << sh;
envrel = srate / 512;
rate(0, reg[0x64/2]);
rate(1, reg[0x6c/2]);
rate(2, reg[0x74/2]);
rate(3, reg[0x7c/2]);
}
bias = (v & 0x3ff) - 0x200;
break;
case 0x90: case 0x92: case 0x94: case 0x96:
case 0x98: case 0x9a: case 0x9c: case 0x9e:
p = ~reg[0x70/2] >> 1 & 32;
for(i = a - 0x90; i < a - 0x90 + 2; i++){
wave[(wpos + 2 * i) & 31 + p] = v >> 4 & 0xf;
wave[(wpos + 2 * i + 1) & 31 + p] = v & 0xf;
v >>= 8;
}
break;
}
}
void
audioinit(void)
{
fd = open("/dev/audio", OWRITE);
if(fd < 0)
sysfatal("open: %r");
sbufp = sbuf;
sndwrite(SOUNDBIAS*2, 0x200);
evsamp.f = sampletick;
addevent(&evsamp, sratediv);
}
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;
}