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games/snes: audio improvements

--- a/sys/src/games/snes/dsp.c

+++ b/sys/src/games/snes/dsp.c

@@ -159,7 +159,7 @@

 	u8int *r;

 	u16int hdrp, dp, sp;

-	u8int hdr;

+	u8int hdr, bp;

 	u16int brr;

 	u8int envst;

@@ -167,7 +167,7 @@

 	u8int init;

 	u16int interp;

-	s16int buf[12];

+	s16int buf[24];

 	u16int pitch;

 	s16int sample, modin;

@@ -243,8 +243,8 @@

 	f = (p->hdr >> 2) & 3;

 	s = p->hdr >> 4;

 	brr = p->brr;

-	s1 = p->buf[7];

-	s2 = p->buf[6];

+	s1 = p->buf[p->bp + 11];

+	s2 = p->buf[p->bp + 10];

 	for(i = 0; i < 4; i++){

 		d = brr >> 12;

 		if(s >= 13)

@@ -273,11 +273,14 @@

 			break;

 		}

 		d = (s16int)(clamp16(d) << 1);

-		p->buf[8 + i] = d;

+		p->buf[p->bp] = d;

+		p->buf[p->bp++ + 12] = d;

 		s1 = d;

 		s2 = s1;

 		brr <<= 4;

 	}

+	if(p->bp == 12)

+		p->bp = 0;

 }

 static s16int

@@ -337,6 +340,8 @@

 		}

 		if((dsp[INT|NON] & 1<<n) != 0)

 			p->sample = noise;

+		else

+			p->sample = interp(p->interp, p->buf + p->bp);

 		p->sample = (((int)p->sample * p->env) >> 11) & ~1;

 		p->modin = p->sample;

 		r[INT|OUTX] = p->sample >> 8;

@@ -362,10 +367,11 @@

 		if(p->init == 1){

 			p->hdrp = p->sp;

 			p->dp = p->hdrp + 1;

+			p->bp = 0;

 		}

 		if(p->interp >= 0x4000 || p->init <= 4 && p->init >= 2){

-			memmove(p->buf, p->buf + 4, 8 * sizeof(s16int));

 			p->brr |= spcmem[++p->dp];

+			decode(p);

 			if(++p->dp == p->hdrp + 9){

 				if((p->hdr & 1) != 0){

 					dsp[INT|ENDX] |= 1<<n;

@@ -374,11 +380,8 @@

 					p->hdrp += 9;

 				p->dp = p->hdrp + 1;

 			}

-			decode(p);

 		}

-		if(p->interp >= 0x4000)

-			p->interp -= 0x4000;

-		p->interp += p->pitch;

+		p->interp = (p->interp & 0x3fff) + p->pitch;

 		if(p->interp >= 0x7fff)

 			p->interp = 0x7fff;

 		break;

@@ -387,7 +390,6 @@

 		samp[1] = clamp16(samp[1] + v);

 		if((dsp[INT|EON] & (1<<n)) != 0)

 			echoin[1] = clamp16(echoin[1] + v); 

-		p->sample = interp(p->interp, p->buf);

 		break;

 	case 7:

 		m = 1<<n;

@@ -503,13 +505,13 @@

 		break;

 	case 29:

 		echo(29);

-		if((dspstate & 64) == 0)

+		if((dspstate & 32) == 0)

 			dsp[NEWKON] &= ~dsp[INT|KON];

 		break;

 	case 30:

 		voice(0, 0x32);

 		echo(30);

-		if((dspstate & 64) == 0){

+		if((dspstate & 32) == 0){

 			dsp[INT|KOFF] = dsp[KOFF];

 			dsp[INT|KON] = dsp[NEWKON];

 		}