Added cycle exact sound handling

diff --git a/src/sound.cpp b/src/sound.cpp
index b67659b0a4f7daeb9cda3e859820b134d8785638..6f06dcde7787e80b28a82eed222a6ceb45fda51a 100755 (executable)
--- 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
        }
 }