new sync using audio DMA

source/ngc/ngc.c

@@ -113,7 +113,6 @@ void reloadrom ()
   audio_init(48000);  /* Audio System initialization */
   ClearGGCodes ();    /* Clear Game Genie patches */
   system_reset ();    /* System Power ON */
-  ogc_audio__reset(); /* reset audio buffers */
 }
 
 /***************************************************************************
@@ -132,8 +131,6 @@ int main (int argc, char *argv[])
   DI_Init();
 #endif
 
-  u16 usBetweenFrames;
-  long long now, prev;
   int RenderedFrameCount = 0;
   int FrameCount = 0;
 
@@ -189,59 +186,29 @@ int main (int argc, char *argv[])
   MainMenu();
   ConfigRequested = 0;
 
-  /* Initialize Frame timings */
-  frameticker = 0;
-  prev = gettime();
-
   /* Emulation Loop */
   while (1)
   {
+    /* audio DMA starting point */
     ogc_audio__start();
 
-    /* Frame synchronization */
-    if (gc_pal != vdp_pal)
+    if (frameticker > 1)
     {
-      /* use timers */
-      usBetweenFrames = vdp_pal ? 20000 : 16666;
-      now = gettime();
-      if (diff_usec(prev, now) > usBetweenFrames)
-      {
-        /* Frame skipping */
-        prev = now;
-        system_frame(1);
-      }
-      else
-      {
-        /* Delay */
-        while (diff_usec(prev, now) < usBetweenFrames) now = gettime();
-
-        /* Render Frame */
-        prev = now;
-        system_frame(0);
-        RenderedFrameCount++;
-      }
-    }
-    else
-    {
-      /* use VSync */
-      if (frameticker > 1)
-      {
         /* Frame skipping */
         frameticker--;
         system_frame (1);
-      }
-      else
-      {
-        /* Delay */
-        while (!frameticker) usleep(10);
-
-        /* Render Frame */
-        system_frame (0);
-        RenderedFrameCount++;
-      }
-
-      frameticker--;
     }
+    else
+    {
+      /* Delay */
+      while (!frameticker) usleep(10);
+
+      /* Render Frame */
+      system_frame (0);
+      RenderedFrameCount++;
+    }
+
+    frameticker--;
 
     /* update video & audio */
     ogc_audio__update();
@@ -268,7 +235,6 @@ int main (int argc, char *argv[])
 
       /* reset frame timings */
       frameticker = 0;
-      prev = gettime();
       FrameCount = 0;
       RenderedFrameCount = 0;
     }

source/ngc/ogc_audio.c

@@ -24,59 +24,55 @@
 #include "shared.h"
 
 /* global datas */
-unsigned char soundbuffer[16][3840] ATTRIBUTE_ALIGN(32);
-int mixbuffer = 0;
+unsigned char soundbuffer[2][3840] ATTRIBUTE_ALIGN(32);
+u8 mixbuffer = 0;
 
-static int playbuffer  = 0;
-static int IsPlaying   = 0;
-static u32 dma_len = 3200;
+static int IsPlaying    = 0;
+static int dma_len      = 3200;
 
-/*** AudioSwitchBuffers
+/*** AudioDmaCallback
      Genesis Plus only provides sound data on completion of each frame.
-     To try to make the audio less choppy, this function is called from both the
-     DMA completion and update_audio.
-     Testing for data in the buffer ensures that there are no clashes.
+     To try to make the audio less choppy, we synchronize emulation with audio DMA
+     This ensure we only update audio framebuffer when DMA is finished
  ***/
-static void AudioSwitchBuffers()
+static void AudioDmaCallback()
 {
-  /* increment soundbuffers index */
-  playbuffer++;
-  playbuffer &= 0xf;
-
-  /* reset audio DMA parameters */
-  AUDIO_InitDMA((u32) soundbuffer[playbuffer], dma_len);
+  frameticker++;
 }
 
 void ogc_audio__init(void)
 {
   AUDIO_Init (NULL);
   AUDIO_SetDSPSampleRate (AI_SAMPLERATE_48KHZ);
- // AUDIO_RegisterDMACallback (AudioSwitchBuffers);
-}
-
-void ogc_audio__reset(void)
-{
-  IsPlaying = 0;
+  AUDIO_RegisterDMACallback (AudioDmaCallback);
   mixbuffer = 0;
-  playbuffer = 0;
-  memset(soundbuffer, 0, 16 * 3840);
+  memset(soundbuffer, 0, 2 * 3840);
 }
 
 void ogc_audio__update(void)
 {
+  /* buffer size */
+  uint32 dma_len = vdp_pal ? 3840 : 3200;
+
+  /* update DMA settings (this will only be taken in account when current DMA finishes) */
+  AUDIO_InitDMA((u32) soundbuffer[mixbuffer], dma_len);
+
   /* flush data from CPU cache */
   DCFlushRange(soundbuffer[mixbuffer], dma_len);
-  AUDIO_InitDMA((u32) soundbuffer[mixbuffer], dma_len);
+
+  /* switch buffer */
+  mixbuffer ^= 1;
 }
 
 void ogc_audio__stop(void)
 {
   /* stop audio DMA */
   AUDIO_StopDMA ();
-  AUDIO_InitDMA((u32) soundbuffer[0], dma_len);
   IsPlaying = 0;
+
+  /* reset audio buffers */
   mixbuffer = 0;
-  playbuffer = 0;
+  memset(soundbuffer, 0, 2 * 3840);
 }
 
 void ogc_audio__start(void)
@@ -86,8 +82,8 @@ void ogc_audio__start(void)
     /* buffer size */
     dma_len = vdp_pal ? 3840 : 3200;
 
-    /* set default DMA parameters */
-    AUDIO_InitDMA((u32) soundbuffer[0], dma_len);
+    /* set first DMA parameters */
+    AUDIO_InitDMA((u32) soundbuffer[1], dma_len);
 
     /* start audio DMA */
     AUDIO_StartDMA();

source/ngc/ogc_audio.h

@@ -24,11 +24,10 @@
 #ifndef _GC_AUDIO_H_
 #define _GC_AUDIO_H_
 
-extern u8 soundbuffer[16][3840];
-extern int mixbuffer;
+extern u8 soundbuffer[2][3840];
+extern u8 mixbuffer;
 
 extern void ogc_audio__init(void);
-extern void ogc_audio__reset(void);
 extern void ogc_audio__stop(void);
 extern void ogc_audio__start(void);
 extern void ogc_audio__update(void);

source/ngc/ogc_video.c

@@ -346,13 +346,6 @@ static inline void draw_square (void)
   GX_End ();
 }
 
-/* retrace handler */
-static void framestart(u32 retraceCnt)
-{
-  /* simply increment the tick counter */
-  frameticker++;
-}
-
 /* Initialize GX */
 static void gxStart(void)
 {
@@ -725,9 +718,6 @@ void ogc_video__init(void)
   /* Set the framebuffer to be displayed at next VBlank */
   VIDEO_SetNextFramebuffer (xfb[0]);
 
-  /* Register Video Retrace handlers */
-  VIDEO_SetPreRetraceCallback(framestart);
-
   /* Enable Video Interface */
   VIDEO_SetBlack (FALSE);
 

source/sound/sound.c

@@ -61,7 +61,7 @@ static inline uint32 psg_sample_cnt(uint8 is_z80)
 /* update FM samples */
 static inline void fm_update()
 {
-  if(snd.fm.curStage - snd.fm.lastStage > 0)
+  if(snd.fm.curStage - snd.fm.lastStage > 1)
   {
     int *tempBuffer[2];
     
@@ -84,7 +84,7 @@ static inline void fm_update()
 /* update PSG samples */
 static inline void psg_update()
 {
-  if(snd.psg.curStage - snd.psg.lastStage > 0)
+  if(snd.psg.curStage - snd.psg.lastStage > 1)
   {
     int16 *tempBuffer = snd.psg.buffer + snd.psg.lastStage;
     SN76489_Update (0, tempBuffer, snd.psg.curStage - snd.psg.lastStage);
@@ -221,11 +221,8 @@ void fm_restore(void)
 /* write FM chip */
 void fm_write(unsigned int cpu, unsigned int address, unsigned int data)
 {
-  if (address & 1)
-  {
-    snd.fm.curStage = fm_sample_cnt(cpu);
-    fm_update();
-  }
+  snd.fm.curStage = fm_sample_cnt(cpu);
+  fm_update();
   _YM2612_Write(address & 3, data);
 }