X-Git-Url: http://shamusworld.gotdns.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fsound.cpp;h=4191928b2c52584c87680ab6c8701ca7990fe0d6;hb=05e3af22c4bd3c40744505a52bbdb24a13fab694;hp=6cc1860d29ccea31ef5eb6c0c9842be42bb4fdac;hpb=af27a070d6a36e5590c5d24ba255300825c25cf9;p=stargem2

diff --git a/src/sound.cpp b/src/sound.cpp
index 6cc1860..4191928 100755
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -10,6 +10,9 @@
 // ---  ----------  ------------------------------------------------------------
 // JLH  06/15/2006  Added changelog ;-)
 // 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.
@@ -24,13 +27,20 @@
 #include "types.h"
 #include "log.h"
 #include "v6808.h"
+#include "timing.h"
 
 //using namespace std;
 
+//#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
 
@@ -43,7 +53,7 @@ void SoundInit(void)
 {
 //	memory_malloc_secure((void **)&DACBuffer, BUFFER_SIZE * sizeof(uint16), "DAC buffer");
 
-	desired.freq = 44100;							// SDL will do conversion on the fly, if it can't get the exact rate. Nice!
+	desired.freq = AUDIO_SAMPLE_RATE;				// SDL will do conversion on the fly, if it can't get the exact rate. Nice!
 	desired.format = AUDIO_U8;						// This uses the native endian (for portability)...
 	desired.channels = 1;
 //	desired.samples = 4096;							// Let's try a 4K buffer (can always go lower)
@@ -53,10 +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");
@@ -81,16 +97,24 @@ void SoundDone(void)
 void SDLSoundCallback(void * userdata, Uint8 * buffer, int length)
 {
 	extern V6808REGS soundCPU;
-	extern uint8 * sram;
+	extern uint8 sram[];
 	int cnt = 0;
 
+	static float overflow = 0.0;
+	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 !!!		
-		Execute6808(&soundCPU, 20);
-		soundCPU.clock -= 20;
+		Execute6808(&soundCPU, time);
+		soundCPU.clock -= time;
 		buffer[cnt++] = sram[0x0400];				// Fill the buffer with the PIA output value
+		time = cyclesToExecuteWholePart;
+		overflow += cyclesToExecuteFractionalPart;
+
+		if (overflow > 1.0)
+		{
+			overflow -= 1.0;
+			time++;
+		}
 	}
 }