Finally fixed problems with demo mode.

[stargem2] / src / sound.cpp

diff --git a/src/sound.cpp b/src/sound.cpp
old mode 100755 (executable)
new mode 100644 (file)
index 6cc1860..b4e9f1d
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -1,36 +1,46 @@
 //
 // Sound Interface v2.0
 //
-// by James L. Hammons
+// by James Hammons
 // (c) 2006 Underground Software
 //
-// JLH = James L. Hammons <jlhamm@acm.org>
+// JLH = James Hammons <jlhamm@acm.org>
 //
 // WHO  WHEN        WHAT
 // ---  ----------  ------------------------------------------------------------
 // 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.
-//   At 44.1 KHz, this works out to 894750 / 44100 = 20.289115646... cycles per sample.
+//   At 44.1 KHz, this works out to 894750 / 44100 = 20.289115646... cycles per
+//   sample.
 //
 
 // Still need to add volume control...
 
 #include "sound.h"
 
-#include "SDL.h"
-#include "types.h"
+#include <SDL2/SDL.h>
+#include <stdint.h>
 #include "log.h"
 #include "v6808.h"
+#include "timing.h"
 
 //using namespace std;
 
+#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_t cyclesToExecuteWholePart;
+static double cyclesToExecuteFractionalPart;
 
 // Private function prototypes
 
@@ -41,22 +51,22 @@ void SDLSoundCallback(void * userdata, Uint8 * buffer, int length);
 //
 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.format = AUDIO_U8;                                              // This uses the native endian (for portability)...
+       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)
-       desired.samples = 2048;                                                 // Let's try a 2K buffer (can always go lower)
+       desired.samples = 2048;                                 // Let's try a 2K buffer (can always go lower)
        desired.callback = SDLSoundCallback;
 
-       if (SDL_OpenAudio(&desired, NULL) < 0)                  // NULL means SDL guarantees what we want
+       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_t)CYCLES_TO_EXECUTE;
+       cyclesToExecuteFractionalPart = CYCLES_TO_EXECUTE - (double)cyclesToExecuteWholePart;
+
        SDL_PauseAudio(false);                                                  // Start playback!
        soundInitialized = true;
        WriteLog("Sound: Successfully initialized.\n");
@@ -81,16 +91,26 @@ void SoundDone(void)
 void SDLSoundCallback(void * userdata, Uint8 * buffer, int length)
 {
        extern V6808REGS soundCPU;
-       extern uint8 * sram;
+       extern uint8_t sram[];
        int cnt = 0;
 
+       static float overflow = 0.0;
+       static uint32_t 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;
-               buffer[cnt++] = sram[0x0400];                           // Fill the buffer with the PIA output value
+               Execute6808(&soundCPU, time);
+               soundCPU.clock -= time;
+//             buffer[cnt++] = sram[0x0400];                           // Fill the buffer with the PIA output value
+               // Do some simple volume control...
+               buffer[cnt++] = sram[0x0400] / 4;                       // Fill the buffer with the PIA output value
+               time = cyclesToExecuteWholePart;
+               overflow += cyclesToExecuteFractionalPart;
+
+               if (overflow > 1.0)
+               {
+                       overflow -= 1.0;
+                       time++;
+               }
        }
 }