[Gamecube/Wii] improved A/V Sync: when VSYNC is enabled, audio resampler output rate is now adjusted (+/-0,1 %) to always keep audio & video synchronized and input lag is reduced by one frame.

core/cd_hw/cdd.c

@@ -2,7 +2,7 @@
  *  Genesis Plus
  *  CD drive processor & CD-DA fader
  *
- *  Copyright (C) 2012-2013  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2012-2014  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
@@ -150,9 +150,6 @@ static const char extensions[SUPPORTED_EXT][16] =
   " - %d.wav"
 };
 
-static blip_t* blip[2];
-
-
 #ifdef USE_LIBTREMOR
 #ifdef DISABLE_MANY_OGG_OPEN_FILES
 static void ogg_free(int i)
@@ -172,14 +169,12 @@ static void ogg_free(int i)
 #endif
 #endif
 
-void cdd_init(blip_t* left, blip_t* right)
+void cdd_init(int samplerate)
 {
   /* CD-DA is running by default at 44100 Hz */
   /* Audio stream is resampled to desired rate using Blip Buffer */
-  blip[0] = left;
+  blip_set_rates(snd.blips[2][0], 44100, samplerate);
-  blip[1] = right;
+  blip_set_rates(snd.blips[2][1], 44100, samplerate);
-  blip_set_rates(left, 44100, snd.sample_rate);
-  blip_set_rates(right, 44100, snd.sample_rate);
 }
 
 void cdd_reset(void)
@@ -953,7 +948,7 @@ void cdd_read_audio(unsigned int samples)
   int16 r = cdd.audio[1];
 
   /* get number of internal clocks (samples) needed */
-  samples = blip_clocks_needed(blip[0], samples);
+  samples = blip_clocks_needed(snd.blips[2][0], samples);
 
   /* audio track playing ? */
   if (!scd.regs[0x36>>1].byte.h && cdd.toc.tracks[cdd.index].fd)
@@ -996,13 +991,13 @@ void cdd_read_audio(unsigned int samples)
         delta = ((ptr[0] * mul) / 1024) - l;
         ptr++;
         l += delta;
-        blip_add_delta_fast(blip[0], i, delta);
+        blip_add_delta_fast(snd.blips[2][0], i, delta);
 
         /* right channel */
         delta = ((ptr[0] * mul) / 1024) - r;
         ptr++;
         r += delta;
-        blip_add_delta_fast(blip[1], i, delta);
+        blip_add_delta_fast(snd.blips[2][1], i, delta);
 
         /* update CD-DA fader volume (one step/sample) */
         if (curVol < endVol)
@@ -1048,7 +1043,7 @@ void cdd_read_audio(unsigned int samples)
         ptr += 2;
   #endif
         l += delta;
-        blip_add_delta_fast(blip[0], i, delta);
+        blip_add_delta_fast(snd.blips[2][0], i, delta);
 
         /* right channel */
   #ifdef LSB_FIRST
@@ -1059,7 +1054,7 @@ void cdd_read_audio(unsigned int samples)
         ptr += 2;
   #endif
         r += delta;
-        blip_add_delta_fast(blip[1], i, delta);
+        blip_add_delta_fast(snd.blips[2][1], i, delta);
 
         /* update CD-DA fader volume (one step/sample) */
         if (curVol < endVol)
@@ -1090,8 +1085,8 @@ void cdd_read_audio(unsigned int samples)
   else
   {
     /* no audio output */
-    if (l) blip_add_delta_fast(blip[0], 0, -l);
+    if (l) blip_add_delta_fast(snd.blips[2][0], 0, -l);
-    if (r) blip_add_delta_fast(blip[1], 0, -r);
+    if (r) blip_add_delta_fast(snd.blips[2][1], 0, -r);
 
     /* save audio output for next frame */
     cdd.audio[0] = 0;
@@ -1099,8 +1094,8 @@ void cdd_read_audio(unsigned int samples)
   }
 
   /* end of Blip Buffer timeframe */
-  blip_end_frame(blip[0], samples);
+  blip_end_frame(snd.blips[2][0], samples);
-  blip_end_frame(blip[1], samples);
+  blip_end_frame(snd.blips[2][1], samples);
 }
 
 

core/cd_hw/cdd.h

@@ -2,7 +2,7 @@
  *  Genesis Plus
  *  CD drive processor & CD-DA fader
  *
- *  Copyright (C) 2012-2013  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2012-2014  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
@@ -98,7 +98,7 @@ typedef struct
 } cdd_t; 
 
 /* Function prototypes */
-extern void cdd_init(blip_t* left, blip_t* right);
+extern void cdd_init(int samplerate);
 extern void cdd_reset(void);
 extern int cdd_context_save(uint8 *state);
 extern int cdd_context_load(uint8 *state);

core/cd_hw/pcm.c

@@ -2,7 +2,7 @@
  *  Genesis Plus
  *  PCM sound chip (315-5476A) (RF5C164 compatible)
  *
- *  Copyright (C) 2012  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2012-2014  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
@@ -41,19 +41,12 @@
 
 #define pcm scd.pcm_hw
 
-static blip_t* blip[2];
+void pcm_init(double clock, int samplerate)
-
-void pcm_init(blip_t* left, blip_t* right)
 {
-  /* number of SCD master clocks run per second */
+  /* PCM chip is running at original rate and is synchronized with SUB-CPU  */
-  double mclk = snd.frame_rate ? (SCYCLES_PER_LINE * (vdp_pal ? 313 : 262) * snd.frame_rate) : SCD_CLOCK;
-
-  /* PCM chips is running at original rate and is synchronized with SUB-CPU  */
   /* Chip output is resampled to desired rate using Blip Buffer. */
-  blip[0] = left;
+  blip_set_rates(snd.blips[1][0], clock / PCM_SCYCLES_RATIO, samplerate);
-  blip[1] = right;
+  blip_set_rates(snd.blips[1][1], clock / PCM_SCYCLES_RATIO, samplerate);
-  blip_set_rates(left, mclk / PCM_SCYCLES_RATIO, snd.sample_rate);
-  blip_set_rates(right, mclk / PCM_SCYCLES_RATIO, snd.sample_rate);
 }
 
 void pcm_reset(void)
@@ -78,8 +71,8 @@ void pcm_reset(void)
   pcm.cycles = 0;
 
   /* clear blip buffers */
-  blip_clear(blip[0]);
+  blip_clear(snd.blips[1][0]);
-  blip_clear(blip[1]);
+  blip_clear(snd.blips[1][1]);
 }
 
 int pcm_context_save(uint8 *state)
@@ -190,14 +183,14 @@ void pcm_run(unsigned int length)
       /* check if PCM left output changed */
       if (pcm.out[0] != l)
       {
-        blip_add_delta_fast(blip[0], i, l-pcm.out[0]);
+        blip_add_delta_fast(snd.blips[1][0], i, l-pcm.out[0]);
         pcm.out[0] = l;
       }
 
       /* check if PCM right output changed */
       if (pcm.out[1] != r)
       {
-        blip_add_delta_fast(blip[1], i, r-pcm.out[1]);
+        blip_add_delta_fast(snd.blips[1][1], i, r-pcm.out[1]);
         pcm.out[1] = r;
       }
     }
@@ -207,21 +200,21 @@ void pcm_run(unsigned int length)
     /* check if PCM left output changed */
     if (pcm.out[0])
     {
-      blip_add_delta_fast(blip[0], 0, -pcm.out[0]);
+      blip_add_delta_fast(snd.blips[1][0], 0, -pcm.out[0]);
       pcm.out[0] = 0;
     }
 
     /* check if PCM right output changed */
     if (pcm.out[1])
     {
-      blip_add_delta_fast(blip[1], 0, -pcm.out[1]);
+      blip_add_delta_fast(snd.blips[1][1], 0, -pcm.out[1]);
       pcm.out[1] = 0;
     }
   }
 
   /* end of blip buffer frame */
-  blip_end_frame(blip[0], length);
+  blip_end_frame(snd.blips[1][0], length);
-  blip_end_frame(blip[1], length);
+  blip_end_frame(snd.blips[1][1], length);
 
   /* update PCM master clock counter */
   pcm.cycles += length * PCM_SCYCLES_RATIO;
@@ -230,7 +223,7 @@ void pcm_run(unsigned int length)
 void pcm_update(unsigned int samples)
 {
   /* get number of internal clocks (samples) needed */
-  unsigned int clocks = blip_clocks_needed(blip[0], samples);
+  unsigned int clocks = blip_clocks_needed(snd.blips[1][0], samples);
 
   /* run PCM chip */
   if (clocks > 0)

core/cd_hw/pcm.h

@@ -2,7 +2,7 @@
  *  Genesis Plus
  *  PCM sound chip (315-5476A) (RF5C164 compatible)
  *
- *  Copyright (C) 2012  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2012-2014  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
@@ -65,7 +65,7 @@ typedef struct
 } pcm_t;
 
 /* Function prototypes */
-extern void pcm_init(blip_t* left, blip_t* right);
+extern void pcm_init(double clock, int rate);
 extern void pcm_reset(void);
 extern int pcm_context_save(uint8 *state);
 extern int pcm_context_load(uint8 *state);

core/sound/sn76489.c

@@ -94,14 +94,9 @@ static const uint16 PSGVolumeValues[16] =
 
 static SN76489_Context SN76489;
 
-static blip_t* blip[2];
+void SN76489_Init(int type)
-
-void SN76489_Init(blip_t* left, blip_t* right, int type)
 {
   int i;
-  
-  blip[0] = left;
-  blip[1] = right;
 
   for (i=0; i<4; i++)
   {
@@ -177,7 +172,7 @@ INLINE void UpdateToneAmplitude(int i, int time)
   if (delta != 0)
   {
     SN76489.ChanOut[i][0] += delta;
-    blip_add_delta_fast(blip[0], time, delta);
+    blip_add_delta_fast(snd.blips[0][0], time, delta);
   }
 
   /* right output */
@@ -185,7 +180,7 @@ INLINE void UpdateToneAmplitude(int i, int time)
   if (delta != 0)
   {
     SN76489.ChanOut[i][1] += delta;
-    blip_add_delta_fast(blip[1], time, delta);
+    blip_add_delta_fast(snd.blips[0][1], time, delta);
   }
 }
 
@@ -199,7 +194,7 @@ INLINE void UpdateNoiseAmplitude(int time)
   if (delta != 0)
   {
     SN76489.ChanOut[3][0] += delta;
-    blip_add_delta_fast(blip[0], time, delta);
+    blip_add_delta_fast(snd.blips[0][0], time, delta);
   }
 
   /* right output */
@@ -207,7 +202,7 @@ INLINE void UpdateNoiseAmplitude(int time)
   if (delta != 0)
   {
     SN76489.ChanOut[3][1] += delta;
-    blip_add_delta_fast(blip[1], time, delta);
+    blip_add_delta_fast(snd.blips[0][1], time, delta);
   }
 }
 

core/sound/sn76489.h

@@ -12,7 +12,7 @@
 #define SN_INTEGRATED  1
 
 /* Function prototypes */
-extern void SN76489_Init(blip_t* left, blip_t* right, int type);
+extern void SN76489_Init(int type);
 extern void SN76489_Reset(void);
 extern void SN76489_Config(unsigned int clocks, int preAmp, int boostNoise, int stereo);
 extern void SN76489_Write(unsigned int clocks, unsigned int data);

core/sound/sound.c

@@ -102,6 +102,7 @@ void sound_init( void )
   }
 
   /* Initialize PSG chip */
+  SN76489_Init((system_hw == SYSTEM_SG) ? SN_DISCRETE : SN_INTEGRATED);
   SN76489_Config(0, config.psg_preamp, config.psgBoostNoise, 0xff);
 }
 

core/state.c

@@ -116,12 +116,10 @@ int state_load(unsigned char *state)
   bufferptr += sound_context_load(&state[bufferptr]);
   if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
   {
-    SN76489_Init(snd.blips[0][0], snd.blips[0][1], SN_INTEGRATED);
     SN76489_Config(0, config.psg_preamp, config.psgBoostNoise, 0xff);
   }
   else
   {
-    SN76489_Init(snd.blips[0][0], snd.blips[0][1], (system_hw == SYSTEM_SG) ? SN_DISCRETE : SN_INTEGRATED);
     SN76489_Config(0, config.psg_preamp, config.psgBoostNoise, io_reg[6]);
   }
 

core/system.c

@@ -60,6 +60,50 @@ static int16 llp,rrp;
 /******************************************************************************************/
 
 int audio_init(int samplerate, double framerate)
+{
+  /* Shutdown first */
+  audio_shutdown();
+
+  /* Clear the sound data context */
+  memset(&snd, 0, sizeof (snd));
+
+  /* Initialize Blip Buffers */
+  snd.blips[0][0] = blip_new(samplerate / 10);
+  snd.blips[0][1] = blip_new(samplerate / 10);
+  if (!snd.blips[0][0] || !snd.blips[0][1])
+  {
+    audio_shutdown();
+    return -1;
+  }
+
+  /* Mega CD sound hardware */
+  if (system_hw == SYSTEM_MCD)
+  {
+    /* allocate blip buffers */
+    snd.blips[1][0] = blip_new(samplerate / 10);
+    snd.blips[1][1] = blip_new(samplerate / 10);
+    snd.blips[2][0] = blip_new(samplerate / 10);
+    snd.blips[2][1] = blip_new(samplerate / 10);
+    if (!snd.blips[1][0] || !snd.blips[1][1] || !snd.blips[2][0] || !snd.blips[2][1])
+    {
+      audio_shutdown();
+      return -1;
+    }
+  }
+
+  /* Initialize resampler internal rates */
+  audio_set_rate(samplerate, framerate);
+
+  /* Set audio enable flag */
+  snd.enabled = 1;
+
+  /* Reset audio */
+  audio_reset();
+
+  return (0);
+}
+
+void audio_set_rate(int samplerate, double framerate)
 {
   /* Number of M-cycles executed per second. */
   /* All emulated chips are kept in sync by using a common oscillator (MCLOCK)            */
@@ -84,25 +128,6 @@ int audio_init(int samplerate, double framerate)
   /*                                                                                      */
   double mclk = framerate ? (MCYCLES_PER_LINE * (vdp_pal ? 313 : 262) * framerate) : system_clock;
 
-  /* Shutdown first */
-  audio_shutdown();
-
-  /* Clear the sound data context */
-  memset(&snd, 0, sizeof (snd));
-
-  /* Initialize audio rates */
-  snd.sample_rate = samplerate;
-  snd.frame_rate  = framerate;
-
-  /* Initialize Blip Buffers */
-  snd.blips[0][0] = blip_new(samplerate / 10);
-  snd.blips[0][1] = blip_new(samplerate / 10);
-  if (!snd.blips[0][0] || !snd.blips[0][1])
-  {
-    audio_shutdown();
-    return -1;
-  }
-
   /* For maximal accuracy, sound chips are running at their original rate using common */
   /* master clock timebase so they remain perfectly synchronized together, while still */
   /* being synchronized with 68K and Z80 CPUs as well. Mixed sound chip output is then */
@@ -110,37 +135,22 @@ int audio_init(int samplerate, double framerate)
   blip_set_rates(snd.blips[0][0], mclk, samplerate);
   blip_set_rates(snd.blips[0][1], mclk, samplerate);
 
-  /* Initialize PSG core */
-  SN76489_Init(snd.blips[0][0], snd.blips[0][1], (system_hw == SYSTEM_SG) ? SN_DISCRETE : SN_INTEGRATED);
-
   /* Mega CD sound hardware */
   if (system_hw == SYSTEM_MCD)
   {
-    /* allocate blip buffers */
+    /* number of SCD master clocks run per second */
-    snd.blips[1][0] = blip_new(samplerate / 10);
+    mclk = framerate ? (SCYCLES_PER_LINE * (vdp_pal ? 313 : 262) * framerate) : SCD_CLOCK;
-    snd.blips[1][1] = blip_new(samplerate / 10);
-    snd.blips[2][0] = blip_new(samplerate / 10);
-    snd.blips[2][1] = blip_new(samplerate / 10);
-    if (!snd.blips[1][0] || !snd.blips[1][1] || !snd.blips[2][0] || !snd.blips[2][1])
-    {
-      audio_shutdown();
-      return -1;
-    }
 
-    /* Initialize PCM core */
+    /* PCM core */
-    pcm_init(snd.blips[1][0], snd.blips[1][1]);
+    pcm_init(mclk, samplerate);
 
-    /* Initialize CDD core */
+    /* CDD core */
-    cdd_init(snd.blips[2][0], snd.blips[2][1]);
+    cdd_init(samplerate);
   }
 
-  /* Set audio enable flag */
+  /* Reinitialize internal rates */
-  snd.enabled = 1;
+  snd.sample_rate = samplerate;
-
+  snd.frame_rate  = framerate;
-  /* Reset audio */
-  audio_reset();
-
-  return (0);
 }
 
 void audio_reset(void)

core/system.h

@@ -106,6 +106,7 @@ extern uint32 system_clock;
 
 /* Function prototypes */
 extern int audio_init(int samplerate, double framerate);
+extern void audio_set_rate(int samplerate, double framerate);
 extern void audio_reset(void);
 extern void audio_shutdown(void);
 extern int audio_update(int16 *buffer);

gx/gx_audio.c

@@ -45,14 +45,12 @@
 /* Number of sound buffers */
 #define SOUND_BUFFER_NUM 3
 
-/* audio DMA status */
-u32 audioStarted;
-
 /* DMA soundbuffers (required to be 32-bytes aligned) */
 static u8 soundbuffer[SOUND_BUFFER_NUM][SOUND_BUFFER_LEN] ATTRIBUTE_ALIGN(32);
 
 /* Current work soundbuffer */
-static u8 mixbuffer;
+static int bufferIndex;
+static int bufferSize;
 
 /* Background music */
 static u8 *Bg_music_ogg = NULL;
@@ -96,9 +94,6 @@ void gx_audio_Init(void)
     }
     fclose(f);
   }
-
-  /* emulation is synchronized with audio hardware by default */
-  audioSync = 1;
 }
 
 /* AUDIO engine shutdown */
@@ -119,50 +114,64 @@ void gx_audio_Shutdown(void)
 
      This function retrieves samples for the frame then set the next DMA parameters 
      Parameters will be taken in account only when current DMA operation is over
+
+     To keep audio & video synchronized, DMA from external memory to audio interface is 
+     started once by video update function when first frame is ready to be displayed, 
+     then anytime video mode is changed and emulation resynchronized to video hardware.
+
+     Once started, audio DMA restarts automatically when all samples have been played.
+     At that time:
+       - if DMA settings have not been updated, previous sound buffer will be played again
+       - if DMA settings are updated too fast, one sound buffer frame might be skipped
+     
+     Therefore, in order to maintain perfect audio playback without any sound skipping  
+     or lagging, we need to make sure frame emulation is completed and this function is 
+     called before previous DMA transfer is finished and after it has been started.
+
+     This is done by synchronizing frame emulation with audio DMA interrupt (which happens
+     anytime audio DMA restarts). When video sync is enabled, to keep emulation in sync 
+     with both video AND audio, an appropriate number of samples is rendered per frame by
+     adjusting emulator output samplerate.
  ***/
-int gx_audio_Update(void)
+int gx_audio_Update(int status)
 {
-  if (audioWait && audioStarted)
-  {
-    return SYNC_WAIT;
-  }
-
   /* Current available soundbuffer */
-  s16 *sb = (s16 *)(soundbuffer[mixbuffer]);
+  s16 *sb = (s16 *)(soundbuffer[bufferIndex]);
 
-  /* Retrieve audio samples (size must be multiple of 32 bytes) */
+  /* Make sure current audio frame has not already been updated */
-  int size = audio_update(sb) * 4;
+  if (status & AUDIO_UPDATE)
-
-  /* Update DMA settings */
-  DCFlushRange((void *)sb, size);
-  AUDIO_InitDMA((u32) sb, size);
-
-  mixbuffer = (mixbuffer + 1) % SOUND_BUFFER_NUM;
-
-  audioWait = audioSync;
-
-  /* Start Audio DMA */
-  /* this is called once to kick-off DMA from external memory to audio interface        */
-  /* DMA operation is automatically restarted when all samples have been sent.          */
-  /* If DMA settings are not updated at that time, previous sound buffer will be used.  */
-  /* Therefore we need to make sure frame emulation is completed before current DMA is  */
-  /* completed, by synchronizing frame emulation with DMA start and also by syncing it  */
-  /* with Video Interrupt and outputing a suitable number of samples per frame.         */
-  if (!audioStarted)
   {
-    /* restart audio DMA */
+    /* Retrieve audio samples (size must be multiple of 32 bytes) */
-    AUDIO_StopDMA();
+    bufferSize = audio_update(sb) * 4;
-    AUDIO_StartDMA();
+    DCFlushRange((void *)sb, bufferSize);
-    audioStarted = 1;
+
+    /* Mark current audio frame as being updated */
+    status &= ~AUDIO_UPDATE;
   }
 
-  return SYNC_AUDIO;  
+  /* Wait until previous audio frame is started before pushing current audio frame into DMA */
+  if ((status & AUDIO_WAIT) && !audioWait)
+  {
+    /* Update audio DMA settings for current frame */
+    AUDIO_InitDMA((u32)sb, bufferSize);
+
+    /* Next soundbuffer */
+    bufferIndex = (bufferIndex + 1) % SOUND_BUFFER_NUM;
+
+    /* Set audio wait flag */
+    audioWait = audioSync;
+
+    /* Current audio frame is ready for upcoming DMA */
+    status &= ~AUDIO_WAIT;
+  }
+
+  return status;  
 }
 
 /*** 
       gx_audio_Start
 
-     This function restart the audio engine
+     This function restarts the audio engine
      This is called when coming back from Main Menu
  ***/
 void gx_audio_Start(void)
@@ -181,11 +190,14 @@ void gx_audio_Start(void)
   /* DMA Interrupt callback */
   AUDIO_RegisterDMACallback(ai_callback);
 
+  /* emulation is synchronized with audio hardware by default */
+  audioSync = AUDIO_WAIT;
+
   /* reset emulation audio processing */
   memset(soundbuffer, 0, sizeof(soundbuffer));
-  audioStarted = 0;
+  audioWait = 0;
-  mixbuffer    = 0;
+  bufferSize = 0;
-  audioWait    = 0;
+  bufferIndex = 0;
 }
 
 /***
@@ -193,7 +205,6 @@ void gx_audio_Start(void)
 
      This function stops current Audio DMA process
      This is called when going back to Main Menu
-     DMA need to be restarted when going back to the game (see above)
  ***/
 void gx_audio_Stop(void)
 {

gx/gx_audio.h

@@ -40,13 +40,12 @@
 #ifndef _GC_AUDIO_H_
 #define _GC_AUDIO_H_
 
-extern u32 audioStarted;
 extern u32 audioSync;
 
 extern void gx_audio_Init(void);
 extern void gx_audio_Shutdown(void);
 extern void gx_audio_Start(void);
 extern void gx_audio_Stop(void);
-extern int gx_audio_Update(void);
+extern int gx_audio_Update(int status);
 
 #endif

gx/gx_input.c

@@ -221,8 +221,8 @@ static void pad_update(s8 chan, u8 i)
   /* Default fast-forward key combo */
   if ((p & PAD_TRIGGER_R) && (PAD_ButtonsDown(0) & PAD_BUTTON_START))
   {
-    audioSync ^= 1;
+    audioSync ^= AUDIO_WAIT;
-    videoSync = audioSync & config.vsync & !(gc_pal ^ vdp_pal);
+    videoSync = (audioSync && config.vsync && (gc_pal != vdp_pal)) ? VIDEO_WAIT : 0;
     return;
   }
 
@@ -1534,8 +1534,8 @@ void gx_input_UpdateEmu(void)
     /* Default fast-forward key combo */
     if (WPAD_ButtonsHeld(0) & (WPAD_BUTTON_MINUS | WPAD_CLASSIC_BUTTON_MINUS))
     {
-      audioSync ^= 1;
+      audioSync ^= AUDIO_WAIT;
-      videoSync = audioSync & config.vsync & !(gc_pal ^ vdp_pal);
+      videoSync = (audioSync && config.vsync && (gc_pal != vdp_pal)) ? VIDEO_WAIT : 0;
       return;
     }
 

gx/gx_video.c

@@ -357,9 +357,42 @@ static u8 d_list[32] ATTRIBUTE_ALIGN(32) =
 /* VSYNC callback */
 static void vi_callback(u32 cnt)
 {
+  /* get audio DMA remaining length */
+  vu16* const _dspReg = (u16*)0xCC005000;
+  u16 remain = _dspReg[29];
+
+  /* adjust desired output samplerate if audio playback is not perfectly in sync with video */
+  if (remain > 0)
+  {
+    int samplerate;
+
+    /* check current audio DMA position (from testing, delta keeps limited to +/- one 32-bit block i.e 8 samples) */
+    if (remain < 5)
+    {
+      /* previous frame DMA is not yet finished (real output rate is slightly slower than expected value) */
+      samplerate = 47950;
+    }
+    else
+    {
+      /* current frame DMA is already started (real output rate is slightly faster than expected value) */
+      samplerate = 48050;
+    }
+
+    /* update resampler ratios if output samplerate has changed */
+    if (samplerate != snd.sample_rate)
+    {
+      /* this will adjust the number of samples returned on next frame(s) */
+      audio_set_rate(samplerate, snd.frame_rate);
+    }
+  }
+
   /* clear VSYNC flag */
   videoWait = 0;
+}
 
+/* XFB update */
+static void xfb_update(u32 cnt)
+{
   /* check if EFB rendering is finished */
   if (drawDone)
   {
@@ -493,8 +526,8 @@ static void gxSetAspectRatio(int *xscale, int *yscale)
 
     /* Horizontal Scaling */
     /* Wii/Gamecube pixel clock = 13.5 Mhz */
-    /* "H32" pixel clock = Master Clock / 10 = 5.3693175 Mhz (NTSC) or 5.3203424 (PAL) */
+    /* "H32" pixel clock = Master Clock / 10 = 5.3693175 Mhz (NTSC) or 5.3203424 Mhz (PAL) */
-    /* "H40" pixel clock = Master Clock / 8 = 6,711646875 Mhz (NTSC) or 6,650428 Mhz (PAL) */
+    /* "H40" pixel clock = Master Clock / 8 = 6.711646875 Mhz (NTSC) or 6.650428 Mhz (PAL) */
     if (config.overscan & 2)
     {
       /* Horizontal borders are emulated */
@@ -505,7 +538,7 @@ static void gxSetAspectRatio(int *xscale, int *yscale)
       }
       else
       {
-        /* 284 "H32" pixels = 284 * Wii/GC pixel clock / "H40" pixel clock = approx. 714 (NTSC) or 721 (PAL) Wii/GC pixels */
+        /* 284 "H32" pixels = 284 * Wii/GC pixel clock / "H32" pixel clock = approx. 714 (NTSC) or 721 (PAL) Wii/GC pixels */
         *xscale = (system_clock == MCLOCK_NTSC) ? 357 : 361; 
       }
     }
@@ -1424,15 +1457,15 @@ void gxTextureClose(gx_texture **p_texture)
 /* Emulation mode -> Menu mode */
 void gx_video_Stop(void)
 {
-  /* disable VSYNC callback */
+  /* disable VSYNC callbacks */
   VIDEO_SetPostRetraceCallback(NULL);
-
+  VIDEO_SetPreRetraceCallback(NULL);
+  
   /* wait for next even field */
   /* this prevents screen artefacts when switching between interlaced & non-interlaced modes */
   do VIDEO_WaitVSync();
   while (!VIDEO_GetNextField());
    
-
   /* adjust TV width */
   vmode->viWidth = config.screen_w;
   vmode->viXOrigin = (VI_MAX_WIDTH_NTSC - vmode->viWidth)/2;
@@ -1478,11 +1511,6 @@ void gx_video_Stop(void)
 /* Menu mode -> Emulation mode */
 void gx_video_Start(void)
 {
-#ifdef HW_RVL
-  VIDEO_SetTrapFilter(config.trap);
-  VIDEO_SetGamma((int)(config.gamma * 10.0));
-#endif
-
   /* TV mode */
   if ((config.tv_mode == 1) || ((config.tv_mode == 2) && vdp_pal))
   {
@@ -1495,16 +1523,6 @@ void gx_video_Start(void)
     gc_pal = 0;
   }
 
-  /* When VSYNC is set to AUTO & console TV mode matches emulated video mode, emulation is synchronized with video hardware as well */
-  if (config.vsync && (gc_pal == vdp_pal))
-  {
-    videoSync = audioSync;
-  }
-  else
-  {
-    videoSync = 0;
-  }
-
   /* Enable progressive or interlaced video mode */
   if (config.render == 2)
   {
@@ -1657,8 +1675,24 @@ void gx_video_Start(void)
   do VIDEO_WaitVSync();
   while (!VIDEO_GetNextField());
 
-  /* VSYNC callback */
+#ifdef HW_RVL
-  VIDEO_SetPostRetraceCallback(vi_callback);
+  VIDEO_SetTrapFilter(config.trap);
+  VIDEO_SetGamma((int)(config.gamma * 10.0));
+#endif
+
+  /* XFB update is done during VBLANK */
+  VIDEO_SetPreRetraceCallback(xfb_update);
+
+  /* Emulation is synchronized with video hardware if VSYNC is set to AUTO & TV mode matches emulated video mode */
+  if (config.vsync && (gc_pal == vdp_pal))
+  {
+    VIDEO_SetPostRetraceCallback(vi_callback);
+    videoSync =  VIDEO_WAIT;
+  }
+  else
+  {
+    videoSync = 0;
+  }
 
   /* restart frame sync */
   videoWait  = 0;
@@ -1667,177 +1701,191 @@ void gx_video_Start(void)
 }
 
 /* GX render update */
-int gx_video_Update(u32 done)
+int gx_video_Update(int status)
 {
-  if (videoWait || done) return SYNC_WAIT;
+  /* make sure current video frame has not already been updated */
-
+  if (status & VIDEO_UPDATE)
-  videoWait = videoSync;
-
-  /* check if display has changed during frame */
-  if (bitmap.viewport.changed & 1)
   {
-    /* update texture size */
+    /* set video wait flag if VSYNC is enabled */
-    vwidth = bitmap.viewport.w + (2 * bitmap.viewport.x);
+    videoWait = videoSync;
-    vheight = bitmap.viewport.h + (2 * bitmap.viewport.y);
 
-    /* interlaced mode */
+    /* check if display has changed during frame */
-    if (config.render && interlaced)
+    if (bitmap.viewport.changed & 1)
     {
-      vheight = vheight << 1;
+      /* update texture size */
-    }
+      vwidth = bitmap.viewport.w + (2 * bitmap.viewport.x);
+      vheight = bitmap.viewport.h + (2 * bitmap.viewport.y);
 
-    /* ntsc filter */
+      /* interlaced mode */
-    if (config.ntsc)
+      if (config.render && interlaced)
-    {
-      vwidth = (reg[12] & 1) ? MD_NTSC_OUT_WIDTH(vwidth) : SMS_NTSC_OUT_WIDTH(vwidth);
-
-      /* texel width must remain multiple of 4 */
-      vwidth  = (vwidth >> 2) << 2;
-    }
-
-    /* initialize texture object */
-    GXTexObj texobj;
-    GX_InitTexObj(&texobj, bitmap.data, vwidth, vheight, GX_TF_RGB565, GX_CLAMP, GX_CLAMP, GX_FALSE);
-
-    /* configure texture filtering */
-    if (!config.bilinear)
-    {
-      GX_InitTexObjLOD(&texobj,GX_NEAR,GX_NEAR_MIP_NEAR,0.0,10.0,0.0,GX_FALSE,GX_FALSE,GX_ANISO_1);
-    }
-
-    /* load texture object */
-    GX_LoadTexObj(&texobj, GX_TEXMAP0);
-
-    /* update rendering mode */
-    if (config.render)
-    {
-      rmode = tvmodes[gc_pal*3 + 2];
-    }
-    else
-    {
-      rmode = tvmodes[gc_pal*3 + interlaced];
-    }
-
-    /* update aspect ratio */
-    gxResetScaler(vwidth);
-
-    /* update GX rendering mode */
-    gxResetMode(rmode, config.vfilter);
-
-    /* update VI mode */
-    VIDEO_Configure(rmode);
-    VIDEO_Flush();
-  }
-
-  /* texture is now directly mapped by the line renderer */
-
-  /* force texture cache update */
-  DCFlushRange(bitmap.data, vwidth*vheight*2);
-  GX_InvalidateTexAll();
-
-  /* disable EFB copy until rendering is done */
-  drawDone = 0;
-
-  /* render textured quad */
-  GX_CallDispList(d_list, 32);
-
-  /* on-screen display */
-  if (osd)
-  {
-    /* reset GX rendering */
-    gxResetRendering(1);
-
-    /* lightgun # 1 screen mark */
-    if (crosshair[0])
-    {
-      if (input.system[0] == SYSTEM_LIGHTPHASER)
       {
-        gxDrawCrosshair(crosshair[0], input.analog[0][0],input.analog[0][1]);
+        vheight = vheight << 1;
+      }
+
+      /* ntsc filter */
+      if (config.ntsc)
+      {
+        vwidth = (reg[12] & 1) ? MD_NTSC_OUT_WIDTH(vwidth) : SMS_NTSC_OUT_WIDTH(vwidth);
+
+        /* texel width must remain multiple of 4 */
+        vwidth  = (vwidth >> 2) << 2;
+      }
+
+      /* initialize texture object */
+      GXTexObj texobj;
+      GX_InitTexObj(&texobj, bitmap.data, vwidth, vheight, GX_TF_RGB565, GX_CLAMP, GX_CLAMP, GX_FALSE);
+
+      /* configure texture filtering */
+      if (!config.bilinear)
+      {
+        GX_InitTexObjLOD(&texobj,GX_NEAR,GX_NEAR_MIP_NEAR,0.0,10.0,0.0,GX_FALSE,GX_FALSE,GX_ANISO_1);
+      }
+
+      /* load texture object */
+      GX_LoadTexObj(&texobj, GX_TEXMAP0);
+
+      /* update rendering mode */
+      if (config.render)
+      {
+        rmode = tvmodes[gc_pal*3 + 2];
       }
       else
       {
-        gxDrawCrosshair(crosshair[0], input.analog[4][0],input.analog[4][1]);
+        rmode = tvmodes[gc_pal*3 + interlaced];
-      }
-    }
-
-    /* lightgun #2 screen mark */
-    if (crosshair[1])
-    {
-      if (input.system[1] == SYSTEM_LIGHTPHASER)
-      {
-        gxDrawCrosshair(crosshair[1], input.analog[4][0],input.analog[4][1]);
-      }
-      else
-      {
-        gxDrawCrosshair(crosshair[1], input.analog[5][0],input.analog[5][1]);
-      }
-    }
-
-    /* CD LEDS */
-    if (cd_leds[1][1])
-    {
-      /* CD LEDS status */
-      u8 mode = scd.regs[0x06 >> 1].byte.h;
-      gxDrawCdLeds(cd_leds[1][(mode >> 1) & 1], cd_leds[0][mode & 1]);
-    }
-
-    /* FPS counter */
-    if (config.fps)
-    {
-      u32 delta = diff_usec(starttime, gettime());
-      frameCount++;
-      if (delta > 1000000)
-      {
-        sprintf(msg,"%3.2f FPS", (float)frameCount * 1000000.0 / (float)delta);
-        frameCount = 0;
-        starttime = gettime();
       }
 
-      /* disable EFB alpha blending for text background */
+      /* update aspect ratio */
-      GX_SetBlendMode(GX_BM_NONE,GX_BL_SRCALPHA,GX_BL_INVSRCALPHA,GX_LO_CLEAR);
+      gxResetScaler(vwidth);
-      GX_Flush();
 
-      gxDrawOnScreenText(msg);
+      /* update GX rendering mode */
+      gxResetMode(rmode, config.vfilter);
+
+      /* update VI mode */
+      VIDEO_Configure(rmode);
+      VIDEO_Flush();
     }
 
-    /* restore texture object */
+    /* texture is now directly mapped by the line renderer */
-    GXTexObj texobj;
+
-    GX_InitTexObj(&texobj, bitmap.data, vwidth, vheight, GX_TF_RGB565, GX_CLAMP, GX_CLAMP, GX_FALSE);
+    /* force texture cache update */
-    if (!config.bilinear)
+    DCFlushRange(bitmap.data, vwidth*vheight*2);
-    {
-      GX_InitTexObjLOD(&texobj,GX_NEAR,GX_NEAR_MIP_NEAR,0.0,10.0,0.0,GX_FALSE,GX_FALSE,GX_ANISO_1);
-    }
-    GX_LoadTexObj(&texobj, GX_TEXMAP0);
     GX_InvalidateTexAll();
 
-    /* restore GX rendering */
+    /* disable EFB copy until rendering is done */
-    gxResetRendering(0);
+    drawDone = 0;
-  }
 
-  /* GX draw interrupt will be triggered when EFB rendering is finished */
+    /* render textured quad */
-  GX_SetDrawDone();
+    GX_CallDispList(d_list, 32);
 
-  if (bitmap.viewport.changed & 1)
+    /* on-screen display */
-  {
+    if (osd)
-    /* clear update flags */
-    bitmap.viewport.changed &= ~1;
-
-    /* field synchronization */
-    VIDEO_WaitVSync();
-    if (rmode->viTVMode & VI_NON_INTERLACE)
     {
-      VIDEO_WaitVSync();
+      /* reset GX rendering */
-    }
+      gxResetRendering(1);
-    else while (VIDEO_GetNextField() != odd_frame)
+
-    {
+      /* lightgun # 1 screen mark */
-      VIDEO_WaitVSync();
+      if (crosshair[0])
+      {
+        if (input.system[0] == SYSTEM_LIGHTPHASER)
+        {
+          gxDrawCrosshair(crosshair[0], input.analog[0][0],input.analog[0][1]);
+        }
+        else
+        {
+          gxDrawCrosshair(crosshair[0], input.analog[4][0],input.analog[4][1]);
+        }
+      }
+
+      /* lightgun #2 screen mark */
+      if (crosshair[1])
+      {
+        if (input.system[1] == SYSTEM_LIGHTPHASER)
+        {
+          gxDrawCrosshair(crosshair[1], input.analog[4][0],input.analog[4][1]);
+        }
+        else
+        {
+          gxDrawCrosshair(crosshair[1], input.analog[5][0],input.analog[5][1]);
+        }
+      }
+
+      /* CD LEDS */
+      if (cd_leds[1][1])
+      {
+        /* CD LEDS status */
+        u8 mode = scd.regs[0x06 >> 1].byte.h;
+        gxDrawCdLeds(cd_leds[1][(mode >> 1) & 1], cd_leds[0][mode & 1]);
+      }
+
+      /* FPS counter */
+      if (config.fps)
+      {
+        u32 delta = diff_usec(starttime, gettime());
+        frameCount++;
+        if (delta > 1000000)
+        {
+          sprintf(msg,"%3.2f FPS", (float)frameCount * 1000000.0 / (float)delta);
+          frameCount = 0;
+          starttime = gettime();
+        }
+
+        /* disable EFB alpha blending for text background */
+        GX_SetBlendMode(GX_BM_NONE,GX_BL_SRCALPHA,GX_BL_INVSRCALPHA,GX_LO_CLEAR);
+        GX_Flush();
+
+        /* display on-screen message */
+        gxDrawOnScreenText(msg);
+      }
+
+      /* restore texture object */
+      GXTexObj texobj;
+      GX_InitTexObj(&texobj, bitmap.data, vwidth, vheight, GX_TF_RGB565, GX_CLAMP, GX_CLAMP, GX_FALSE);
+      if (!config.bilinear)
+      {
+        GX_InitTexObjLOD(&texobj,GX_NEAR,GX_NEAR_MIP_NEAR,0.0,10.0,0.0,GX_FALSE,GX_FALSE,GX_ANISO_1);
+      }
+      GX_LoadTexObj(&texobj, GX_TEXMAP0);
+      GX_InvalidateTexAll();
+
+      /* restore GX rendering */
+      gxResetRendering(0);
     }
 
-    /* Audio DMA need to be resynchronized with VSYNC */                    
+    /* Do not wait for EFB rendering, GX draw interrupt will be triggered when it is finished */
-    audioStarted = 0;
+    GX_SetDrawDone();
+
+    /* check interlaced mode change */
+    if (bitmap.viewport.changed & 4)
+    {
+      /* "original" mode */
+      if (!config.render && config.vsync && (gc_pal == vdp_pal))
+      {
+        /* framerate has changed, reinitialize audio timings */
+        audio_init(snd.sample_rate, get_framerate());
+      }
+
+      /* clear flag */
+      bitmap.viewport.changed &= ~4;
+    }
+
+    /* Check if video mode has changed */
+    if (bitmap.viewport.changed & 1)
+    {
+      /* clear viewport update flags */
+      bitmap.viewport.changed &= ~1;
+
+      /* field synchronization */
+      do VIDEO_WaitVSync();
+      while (VIDEO_GetNextField() != odd_frame);
+
+      /* resynchronize audio playback with video */                    
+      AUDIO_StopDMA();
+      AUDIO_StartDMA();
+    }
   }
 
-  return SYNC_VIDEO;
+  /* wait until current video frame starts before emulating next frame */
+  return ((status & ~(VIDEO_WAIT|VIDEO_UPDATE)) | videoWait);
 }
 
 /* Initialize VIDEO subsystem */

gx/gx_video.h

@@ -99,6 +99,6 @@ extern void gx_video_Init(void);
 extern void gx_video_Shutdown(void);
 extern void gx_video_Start(void);
 extern void gx_video_Stop(void);
-extern int gx_video_Update(u32 done);
+extern int gx_video_Update(int status);
 
 #endif

gx/main.c

@@ -57,9 +57,6 @@ extern bool sdio_Deinitialize();
 extern void USBStorage_Deinitialize();
 #endif
 
-/* output samplerate, adjusted to take resampler precision in account */
-#define SAMPLERATE_48KHZ 47992
-
 u32 Shutdown = 0;
 u32 ConfigRequested = 1;
 
@@ -153,28 +150,14 @@ static void run_emulation(void)
         system_frame_scd(0);
 
         /* audio/video sync */
-        sync = SYNC_WAIT;
+        sync = VIDEO_WAIT | VIDEO_UPDATE | AUDIO_WAIT | AUDIO_UPDATE;
-        while (sync != (SYNC_VIDEO | SYNC_AUDIO))
+        while (sync)
         {
-          /* update video */
-          sync |= gx_video_Update(sync & SYNC_VIDEO);
-
           /* update audio */
-          sync |= gx_audio_Update();
+          sync &= gx_audio_Update(sync);
-        }
 
-        /* check interlaced mode change */
+          /* update video */
-        if (bitmap.viewport.changed & 4)
+          sync &= gx_video_Update(sync);
-        {
-          /* VSYNC "original" mode */
-          if (!config.render && config.vsync && (gc_pal == vdp_pal))
-          {
-            /* framerate has changed, reinitialize audio timings */
-            audio_init(SAMPLERATE_48KHZ, get_framerate());
-          }
-
-          /* clear flag */
-          bitmap.viewport.changed &= ~4;
         }
       }
     }
@@ -187,28 +170,14 @@ static void run_emulation(void)
         system_frame_gen(0);
 
         /* audio/video sync */
-        sync = SYNC_WAIT;
+        sync = VIDEO_WAIT | VIDEO_UPDATE | AUDIO_WAIT | AUDIO_UPDATE;
-        while (sync != (SYNC_VIDEO | SYNC_AUDIO))
+        while (sync)
         {
-          /* update video */
-          sync |= gx_video_Update(sync & SYNC_VIDEO);
-
           /* update audio */
-          sync |= gx_audio_Update();
+          sync &= gx_audio_Update(sync);
-        }
 
-        /* check interlaced mode change */
+          /* update video */
-        if (bitmap.viewport.changed & 4)
+          sync &= gx_video_Update(sync);
-        {
-          /* VSYNC "original" mode */
-          if (!config.render && config.vsync && (gc_pal == vdp_pal))
-          {
-            /* framerate has changed, reinitialize audio timings */
-            audio_init(SAMPLERATE_48KHZ, get_framerate());
-          }
-
-          /* clear flag */
-          bitmap.viewport.changed &= ~4;
         }
       }
     }
@@ -221,28 +190,14 @@ static void run_emulation(void)
         system_frame_sms(0);
 
         /* audio/video sync */
-        sync = SYNC_WAIT;
+        sync = VIDEO_WAIT | VIDEO_UPDATE | AUDIO_WAIT | AUDIO_UPDATE;
-        while (sync != (SYNC_VIDEO | SYNC_AUDIO))
+        while (sync)
         {
-          /* update video */
-          sync |= gx_video_Update(sync & SYNC_VIDEO);
-
           /* update audio */
-          sync |= gx_audio_Update();
+          sync &= gx_audio_Update(sync);
-        }
 
-        /* check interlaced mode change (PBC mode only) */
+          /* update video */
-        if (bitmap.viewport.changed & 4)
+          sync &= gx_video_Update(sync);
-        {
-          /* "original" mode */
-          if (!config.render && config.vsync && (gc_pal == vdp_pal))
-          {
-            /* framerate has changed, reinitialize audio timings */
-            audio_init(SAMPLERATE_48KHZ, get_framerate());
-          }
-
-          /* clear flag */
-          bitmap.viewport.changed &= ~4;
         }
       }
     }
@@ -316,7 +271,7 @@ void reloadrom(void)
   {
     /* Initialize audio emulation */
     interlaced = 0;
-    audio_init(SAMPLERATE_48KHZ, get_framerate());
+    audio_init(48000, get_framerate());
      
     /* System Power-On */
     system_init();

gx/osd.h

@@ -71,9 +71,10 @@
 
 #define VERSION "Genesis Plus GX 1.7.5"
 
-#define SYNC_WAIT  0
+#define VIDEO_WAIT    0x01
-#define SYNC_VIDEO 1
+#define AUDIO_WAIT    0x02
-#define SYNC_AUDIO 2
+#define VIDEO_UPDATE  0x04
+#define AUDIO_UPDATE  0x08
 
 /* globals */
 extern void legal(void);