X-Git-Url: http://shamusworld.gotdns.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fsound.cpp;fp=src%2Fsound.cpp;h=4191928b2c52584c87680ab6c8701ca7990fe0d6;hb=00f99074bf49f4d52d17a534dd3d4e451f4bbc59;hp=2f7522047072082c2b3c32fba6a6e04be0f340d4;hpb=2879315d07ce59a7996bc8a137c3b66ae018013a;p=stargem2

diff --git a/src/sound.cpp b/src/sound.cpp
index 2f75220..4191928 100755
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -12,6 +12,7 @@
 // JLH  06/15/2006  Scrubbed all BYTE, WORD & DWORD references from the code
 // JLH  02/10/2009  Fixed sound IRQ callback so that CPU samples are taken at
 //                  cycle exact boundaries
+// JLH  07/21/2009  Moved numeric constants into macros for sanity's sake
 //
 // Notes:
 //   The sound CPU (6808) runs at 894,750 (3,579,000 / 4) Hz.
@@ -30,12 +31,16 @@
 
 //using namespace std;
 
-#define AUDIO_SAMPLE_RATE	44100
+//#define AUDIO_SAMPLE_RATE				44100.0
+#define AUDIO_SAMPLE_RATE				48000.0
+#define CYCLES_TO_EXECUTE				(M6808_CLOCK_SPEED_IN_HZ / AUDIO_SAMPLE_RATE)
 
 // Local variables
 
-SDL_AudioSpec desired;
-bool soundInitialized = false;
+static SDL_AudioSpec desired;
+static bool soundInitialized = false;
+static uint32 cyclesToExecuteWholePart;
+static double cyclesToExecuteFractionalPart;
 
 // Private function prototypes
 
@@ -58,10 +63,16 @@ void SoundInit(void)
 	if (SDL_OpenAudio(&desired, NULL) < 0)			// NULL means SDL guarantees what we want
 	{
 		WriteLog("Sound: Failed to initialize SDL sound.\n");
-//		exit(1);
 		return;
 	}
 
+	// Setup clock cycles & etc.
+	cyclesToExecuteWholePart = (uint32)CYCLES_TO_EXECUTE;
+	cyclesToExecuteFractionalPart = CYCLES_TO_EXECUTE - (double)cyclesToExecuteWholePart;
+#if 0
+printf("Cycles to execute: %lf; cycles W: %u; cycles F: %lf\n", CYCLES_TO_EXECUTE, cyclesToExecuteWholePart, cyclesToExecuteFractionalPart);
+#endif
+
 	SDL_PauseAudio(false);							// Start playback!
 	soundInitialized = true;
 	WriteLog("Sound: Successfully initialized.\n");
@@ -80,15 +91,6 @@ void SoundDone(void)
 	}
 }
 
-/*
-The way to determine the # of cycles for each sample is to take the CPU clock frequency
-and divide by the sample rate.
-
-Like so:
-double cycles = M6808_CLOCK_SPEED_IN_HZ / AUDIO_SAMPLE_RATE;
-Then we need to separate out the fractional part from the integer part.
-*/
-
 //
 // Sound card callback handler
 //
@@ -98,54 +100,21 @@ void SDLSoundCallback(void * userdata, Uint8 * buffer, int length)
 	extern uint8 sram[];
 	int cnt = 0;
 
-#define CYCLE_EXACT_SOUND
-#ifdef CYCLE_EXACT_SOUND
 	static float overflow = 0.0;
-	static uint32 time = 20;
-#endif
+	static uint32 time = cyclesToExecuteWholePart;
 
 	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 !!! [DONE]
-/*
-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);
 		soundCPU.clock -= time;
-#else
-		Execute6808(&soundCPU, 20);
-		soundCPU.clock -= 20;
-#endif
 		buffer[cnt++] = sram[0x0400];				// Fill the buffer with the PIA output value
-#ifdef CYCLE_EXACT_SOUND
-		overflow += 0.289115646;					// Fractional part of CPU cycles...
+		time = cyclesToExecuteWholePart;
+		overflow += cyclesToExecuteFractionalPart;
 
 		if (overflow > 1.0)
 		{
 			overflow -= 1.0;
-			time = 21;
+			time++;
 		}
-		else
-			time = 20;
-#endif
 	}
 }