From 020e517dc5cf78b1f20e17f0e3f3811d8e78ab62 Mon Sep 17 00:00:00 2001
From: Shamus Hammons <jlhamm@acm.org>
Date: Wed, 11 Feb 2009 05:03:29 +0000
Subject: [PATCH] Added cycle exact sound handling

---
 src/sound.cpp | 42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/sound.cpp b/src/sound.cpp
index b67659b..6f06dcd 100755
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -85,13 +85,53 @@ void SDLSoundCallback(void * userdata, Uint8 * buffer, int length)
 	extern uint8 sram[];
 	int cnt = 0;
 
+#define CYCLE_EXACT_SOUND
+#ifdef CYCLE_EXACT_SOUND
+	float overflow = 0.0;
+	uint32 time = 20;
+#endif
+
 	while (cnt != length)
 	{
 		// This is close, but not cycle exact (exact would be 20.289115646...)
 
-//Need to figure out how to get that fraction to execute... !!! FIX !!!		
+//Need to figure out how to get that fraction to execute... !!! FIX !!!
+/*
+One way would be to use a fractional accumulator, then subtract 1 every
+time it overflows. Like so:
+
+double overflow = 0;
+uint32 time = 20;
+while (!done)
+{
+	Execute6808(&soundCPU, time);
+	overflow += 0.289115646;
+	if (overflow > 1.0)
+	{
+		overflow -= 1.0;
+		time = 21;
+	}
+	else
+		time = 20;
+}
+*/
+#ifdef CYCLE_EXACT_SOUND
+		Execute6808(&soundCPU, time);
+#else
 		Execute6808(&soundCPU, 20);
+#endif
 		soundCPU.clock -= 20;
 		buffer[cnt++] = sram[0x0400];				// Fill the buffer with the PIA output value
+#ifdef CYCLE_EXACT_SOUND
+		overflow += 0.289115646;
+
+		if (overflow > 1.0)
+		{
+			overflow -= 1.0;
+			time = 21;
+		}
+		else
+			time = 20;
+#endif
 	}
 }
-- 
2.37.2