From d2618d03f5e17c3deed916e56b5e4f282dc093f2 Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Sat, 12 Apr 2014 22:25:26 +0200
Subject: [PATCH] games/snes: upsample audio to 44100 hz instead of setting
 audio device frequency

used to set audio device frequency thru /dev/volume tho
only ac97 driver supports this. as a quick work arround,
upsample the 32000 hz audio signal to 44100 hz (without
any interpolation).

move the sample buffer room check from audiosample() into
dspstep() so that when the buffer is full (shouldnt happen),
we wont advance dspstate so samples will not get dropped.
---
 sys/src/games/snes/dsp.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/sys/src/games/snes/dsp.c b/sys/src/games/snes/dsp.c
index 0351d1c01..5ccdb97e6 100644
--- a/sys/src/games/snes/dsp.c
+++ b/sys/src/games/snes/dsp.c
@@ -42,31 +42,30 @@ enum {
 
 enum { RELEASE, ATTACK, DECAY, SUSTAIN };
 
+enum { Freq = 44100 };
 static s16int sbuf[2*2000], *sbufp;
+static int stime;
 static int fd;
 
 void
 audioinit(void)
 {
-	int cfd;
-	static char c[] = "speed 32000";
-
 	fd = open("/dev/audio", OWRITE);
 	if(fd < 0)
-		return;
-	cfd = open("/dev/volume", OWRITE);
-	if(cfd >= 0)
-		write(cfd, c, sizeof(c));
+		sysfatal("open: %r");
 	sbufp = sbuf;
 }
 
 static void
 audiosample(s16int *s)
 {
-	if(sbufp < sbuf + nelem(sbuf)){
-		*sbufp++ = s[0];
-		*sbufp++ = s[1];
-	}
+	stime -= 1<<16;
+	do {
+		sbufp[0] = s[0];
+		sbufp[1] = s[1];
+		sbufp += 2;
+		stime += (32000<<16)/Freq;
+	} while(stime < 0);
 }
 
 int
@@ -459,7 +458,7 @@ echo(int s)
 void
 dspstep(void)
 {
-	if(sbufp == nil)
+	if(sbufp == nil || sbufp >= sbuf+nelem(sbuf)-2)
 		return;
 	switch(dspstate++ & 31){
 	case  0: voice(0, 5); voice(1, 2); break;