audio: Pretend all audio is looping U8 samples. Make that work, sort of.

1 files changed, 45 insertions, 5 deletions

diff --git a/audio.c b/audio.c
index 7994609..a9abcfd 100644
--- a/audio.c
+++ b/audio.c
@@ -60,16 +60,56 @@ static u32 get_channel_bit(u32 ch, u32 reg)
 	return (mem[reg] >> ch) & 1;
 }
 
+static u32 n_left[24];
+static u16 bits_left[24];
+static void do_next_sample(u32 ch)
+{
+loop:
+	if (n_left[ch] == 0) {
+		u32 addr = ((mem[0x3001 + 16*ch] & 0x3f) << 16) | mem[0x3000 + 16*ch];
+		bits_left[ch] = mem[addr];
+		if (bits_left[ch] == 0xffff) {
+			mem[0x3000 + 16*ch] = mem[0x3002 + 16*ch];
+			mem[0x3001 + 16*ch] &= 0xffc0;
+			mem[0x3001 + 16*ch] |= (mem[0x3001 + 16*ch] >> 6) & 0x3f;
+			goto loop;
+		}
+		n_left[ch] = 2;
+		mem[0x3000 + 16*ch]++;
+		if (mem[0x3000 + 16*ch] == 0)
+			mem[0x3001 + 16*ch]++;	// XXX: mask?
+//printf("--> addr = %06x\n", addr);
+	}
+
+	mem[0x300b + 16*ch] = bits_left[ch] << 8;
+	bits_left[ch] >>= 8;
+	n_left[ch]--;
+}
+
 #define FREQ 440
 static u16 next_channel_sample(u32 ch)
 {
 //	if (ch)
 //		return 0x8000;
-	static u32 xxx[24] = {0};
-	u16 sample = 0x8000 + (int)(20000*sin(2*M_PI*xxx[ch]*FREQ/281250));
-	xxx[ch]++;
-	if (xxx[ch] == 281250)
-		xxx[ch] = 0;
+
+//	static u32 xxx[24] = {0};
+//	u16 sample = 0x8000 + (int)(20000*sin(2*M_PI*xxx[ch]*FREQ/281250));
+//	xxx[ch]++;
+//	if (xxx[ch] == 281250)
+//		xxx[ch] = 0;
+//	return sample;
+
+	u16 sample = mem[0x300b + 16*ch];
+	u32 acc = (mem[0x3201 + 16*ch] << 16) | mem[0x3205 + 16*ch];
+	u32 inc = (mem[0x3200 + 16*ch] << 16) | mem[0x3204 + 16*ch];
+	acc += inc;
+	if (acc >= 0x80000) {
+		do_next_sample(ch);
+		acc -= 0x80000;
+	}
+	mem[0x3201 + 16*ch] = acc >> 16;
+	mem[0x3205 + 16*ch] = acc;
+
 	return sample;
 }