added GX_Flush(), documented sound rendering core

source/ngc/ngc.c

@@ -79,7 +79,7 @@ static void load_bios()
 
 static void init_machine (void)
 {
-  /* Allocate cart_rom here */
+  /* Allocate cart_rom here ( 10 MBytes ) */
   cart_rom = memalign(32, 10 * 1024 * 1024);
 
   /* BIOS support */
@@ -194,16 +194,16 @@ int main (int argc, char *argv[])
 
     if (frameticker > 1)
     {
-        /* Frame skipping */
+        /* frameskipping */
         frameticker--;
         system_frame (1);
     }
     else
     {
-      /* Delay */
+      /* frame sync */
       while (!frameticker) usleep(10);
 
-      /* Render Frame */
+      /* frame rendering */
       system_frame (0);
       RenderedFrameCount++;
     }
@@ -214,7 +214,7 @@ int main (int argc, char *argv[])
     ogc_audio__update();
     ogc_video__update();
 
-    /* Check rendered frames (FPS) */
+    /* check rendered frames (FPS) */
     FrameCount++;
     if (FrameCount == vdp_rate)
     {
@@ -226,14 +226,14 @@ int main (int argc, char *argv[])
     /* Check for Menu request */
     if (ConfigRequested)
     {
-      /* stop AUDIO */
+      /* stop Audio */
       ogc_audio__stop();
 
       /* go to menu */
       MainMenu ();
       ConfigRequested = 0;
 
-      /* reset frame timings */
+      /* reset frame sync */
       frameticker = 0;
       FrameCount = 0;
       RenderedFrameCount = 0;

source/ngc/ogc_audio.c

@@ -23,71 +23,102 @@
 
 #include "shared.h"
 
-/* global datas */
+/* DMA soundbuffers (required to be 32-bytes aligned)
-unsigned char soundbuffer[2][3840] ATTRIBUTE_ALIGN(32);
+   Length is dimensionned for one frame of emulation (see below)
-u8 mixbuffer = 0;
+   To prevent audio clashes, we use double buffering technique:
+    one buffer is the active DMA buffer
+    the other one is the current work buffer (updated during frame emulation)
+   We do not need more since frame emulation is synchronized with DMA execution
+*/
+u8 soundbuffer[2][3840] ATTRIBUTE_ALIGN(32);
 
+/* Current work soundbuffer */
+u8 mixbuffer = 1;
+
+/* Current DMA status (1: DMA in progress, 0: DMA stopped) */ 
 static int IsPlaying  = 0;
+
+/* Current DMA length (required to be a factor of 32-bytes)
+   length is calculated regarding current emulation timings:
+    PAL timings : 50 frames/sec, 48000 samples/sec = 960 samples per frame = 3840 bytes (16 bits stereo samples)
+    NTSC timings: 60 frames/sec, 48000 samples/sec = 800 samples per frame = 3200 bytes (16 bits stereo samples)
+*/
 static int dma_len  = 3200;
 
-/*** AudioDmaCallback
+/*** 
+      AudioDmaCallback
+
      Genesis Plus only provides sound data on completion of each frame.
-     To try to make the audio less choppy, we synchronize emulation with audio DMA
+     To try to make the audio less choppy, we synchronize frame emulation with audio DMA
-     This ensure we only update audio framebuffer when DMA is finished
+     This ensure we don't access current active audiobuffer until a new DMA has been started
+     This also makes frame emulation sync completely independent from video sync
  ***/
 static void AudioDmaCallback()
 {
   frameticker++;
 }
 
+/***
+      ogc_audio__init
+
+     This function initializes the Audio Interface and DMA callback
+     Default samplerate is set to 48khZ
+ ***/
 void ogc_audio__init(void)
 {
   AUDIO_Init (NULL);
   AUDIO_SetDSPSampleRate (AI_SAMPLERATE_48KHZ);
   AUDIO_RegisterDMACallback (AudioDmaCallback);
-  mixbuffer = 0;
   memset(soundbuffer, 0, 2 * 3840);
 }
 
+/*** 
+      ogc_audio__update
+
+     This function is called at the end of each frame, once the current soundbuffer has been updated
+     DMA sync and switching ensure we never access the active DMA buffer
+     This function set the next DMA buffer 
+     Parameters will be taken in account ONLY when current DMA has finished
+ ***/
 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);
-
-  /* switch buffer */
   mixbuffer ^= 1;
 }
 
-void ogc_audio__stop(void)
+/*** 
-{
+      ogc_audio__start
-  /* stop audio DMA */
-  AUDIO_StopDMA ();
-  IsPlaying = 0;
-
-  /* reset audio buffers */
-  mixbuffer = 0;
-  memset(soundbuffer, 0, 2 * 3840);
-}
 
+     This function restarts Audio DMA processing
+     This is called only ONCE, when emulation loop starts or when coming back from Main Menu
+     DMA length is used for frame emulation synchronization (PAL & NTSC timings)
+     DMA is *automatically* restarted once the configured audio length has been output
+     When DMA parameters are not updated, same soundbuffer is played again
+     DMA parameters can be updated using successive calls to AUDIO_InitDMA (see above)
+ ***/
 void ogc_audio__start(void)
 {
   if (!IsPlaying)
   {
-    /* buffer size */
     dma_len = vdp_pal ? 3840 : 3200;
-
+    AUDIO_InitDMA((u32) soundbuffer[0], dma_len);
-    /* set first DMA parameters */
-    AUDIO_InitDMA((u32) soundbuffer[1], dma_len);
-
-    /* start audio DMA */
     AUDIO_StartDMA();
-
     IsPlaying = 1;
   }
 }
+
+/***
+      ogc_audio__stop
+
+     This function reset current Audio DMA process and clear soundbuffers
+     This is called when going back to Main Menu
+     DMA need to be restarted when going back to the game (see above)
+ ***/
+void ogc_audio__stop(void)
+{
+  AUDIO_StopDMA ();
+  IsPlaying = 0;
+  mixbuffer = 1;
+  memset(soundbuffer, 0, 2 * 3840);
+}

source/ngc/ogc_video.c

@@ -377,10 +377,11 @@ static void gxStart(void)
 
   /*** Reset XFB ***/
   GX_CopyDisp (xfb[whichfb ^ 1], GX_TRUE);
+  GX_Flush ();
 
   /*** Initialize texture data ***/
-  texturemem = memalign(32, TEX_WIDTH * TEX_HEIGHT * 2);
+  texturemem = memalign(32, TEX_SIZE);
-  memset (texturemem, 0, TEX_WIDTH * TEX_HEIGHT * 2);
+  memset (texturemem, 0, TEX_SIZE);
 
   /*** Initialize renderer */
   draw_init();
@@ -545,6 +546,7 @@ void ogc_video__reset()
   GX_SetPixelFmt (rmode->aa ? GX_PF_RGB565_Z16 : GX_PF_RGB8_Z24, GX_ZC_LINEAR);
   guOrtho(p, rmode->efbHeight/2, -(rmode->efbHeight/2), -(rmode->fbWidth/2), rmode->fbWidth/2, 100, 1000);
   GX_LoadProjectionMtx (p, GX_ORTHOGRAPHIC);
+  GX_Flush ();
 
   /* Software NTSC filter */
   if (config.ntsc == 1)