fixed audio/video synchronization in interlaced & progressive modes

source/gx/gui/menu.c

@@ -988,7 +988,7 @@ static void systemmenu ()
 
     switch (ret)
     {
-      case 0:  /*** Region Force ***/
+      case 0:  /*** Force Region ***/
         config.region_detect = (config.region_detect + 1) % 4;
         if (config.region_detect == 0)
           sprintf (items[0].text, "Console Region: AUTO");
@@ -1004,18 +1004,13 @@ static void systemmenu ()
           /* reset console region */
           region_autodetect();
 
-          /* update framerate */
-          if (vdp_pal)
-            framerate = 50.0;
-          else
-            framerate = ((config.tv_mode == 0) || (config.tv_mode == 2)) ? (1000000.0/16715.0) : 60.0;
-
           /* save YM2612 context */
           temp = memalign(32,YM2612GetContextSize());
           if (temp)
             memcpy(temp, YM2612GetContextPtr(), YM2612GetContextSize());
 
           /* reinitialize all timings */
+          framerate = vdp_pal ? 50.0 : ((config.tv_mode == 1) ? 60.0 : ((config.render || interlaced) ? 59.94 : (1000000.0/16715.0)));
           audio_init(snd.sample_rate, framerate);
           system_init();
 
@@ -1212,6 +1207,27 @@ static void videomenu ()
             config.render = 0;
           }
         }
+
+        if (!vdp_pal && cart.romsize)
+        {
+          /* save YM2612 context */
+          temp = memalign(32,YM2612GetContextSize());
+          if (temp)
+            memcpy(temp, YM2612GetContextPtr(), YM2612GetContextSize());
+
+          /* reinitialize audio timings */
+          framerate = (config.tv_mode == 1) ? 60.0 : ((config.render || interlaced) ? 59.94 : (1000000.0/16715.0));
+          audio_init(snd.sample_rate, framerate);
+          sound_init();
+
+          /* restore YM2612 context */
+          if (temp)
+          {
+            YM2612Restore(temp);
+            free(temp);
+          }
+        }
+
         if (config.render == 1)
           sprintf (items[0].text,"Display: INTERLACED");
         else if (config.render == 2)
@@ -1225,26 +1241,24 @@ static void videomenu ()
         {
           config.tv_mode = (config.tv_mode + 1) % 3;
 
-          /* update framerate */
+          if (!vdp_pal && cart.romsize)
-          if (vdp_pal)
-            framerate = 50.0;
-          else
-            framerate = ((config.tv_mode == 0) || (config.tv_mode == 2)) ? (1000000.0/16715.0) : 60.0;
-
-          /* save YM2612 context */
-          temp = memalign(32,YM2612GetContextSize());
-          if (temp)
-            memcpy(temp, YM2612GetContextPtr(), YM2612GetContextSize());
-
-          /* reinitialize audio timings */
-          audio_init(snd.sample_rate, framerate);
-          sound_init();
-
-          /* restore YM2612 context */
-          if (temp)
           {
-            YM2612Restore(temp);
+            /* save YM2612 context */
-            free(temp);
+            temp = memalign(32,YM2612GetContextSize());
+            if (temp)
+              memcpy(temp, YM2612GetContextPtr(), YM2612GetContextSize());
+
+            /* reinitialize audio timings */
+            framerate = (config.tv_mode == 1) ? 60.0 : ((config.render || interlaced) ? 59.94 : (1000000.0/16715.0));
+            audio_init(snd.sample_rate, framerate);
+            sound_init();
+
+            /* restore YM2612 context */
+            if (temp)
+            {
+              YM2612Restore(temp);
+              free(temp);
+            }
           }
 
           if (config.tv_mode == 0)

source/gx/gx_audio.c

@@ -71,7 +71,10 @@ void gx_audio_Init(void)
     stat(fname, &filestat);
     Bg_music_ogg_size = filestat.st_size;
     Bg_music_ogg = memalign(32,Bg_music_ogg_size);
-    if (Bg_music_ogg) fread(Bg_music_ogg,1,Bg_music_ogg_size,f);
+    if (Bg_music_ogg)
+    {
+      fread(Bg_music_ogg,1,Bg_music_ogg_size,f);
+    }
     fclose(f);
   }
 }
@@ -84,7 +87,9 @@ void gx_audio_Shutdown(void)
   ASND_Pause(1);
   ASND_End();
   if (Bg_music_ogg)
+  {
     free(Bg_music_ogg);
+  }
 }
 
 /*** 
@@ -111,24 +116,19 @@ void gx_audio_Update(void)
   /* Therefore we need to make sure frame emulation is completed before current DMA is  */
   /* completed, either by synchronizing frame emulation with DMA start or by syncing it */
   /* with Vertical Interrupt and outputing a suitable number of samples per frame.      */
-  /* In 60hz mode, VSYNC period is actually 16715 ms which is 802.32 samples at 48kHz.  */
   /*                                                                                    */
   /* In both cases, audio DMA need to be synchronized with VSYNC and therefore need to  */
   /* be resynchronized (restarted) every time video settings are changed (hopefully,    */
   /* this generally happens while no music is played.                                   */                    
   if (!audioStarted)
   {
-    audioStarted = 1;
-
-    /* when not using 60hz mode, frame emulation is synchronized with Audio Interface DMA */
-    if (gc_pal | vdp_pal)
-      AUDIO_RegisterDMACallback(ai_callback);
-
     /* restart audio DMA */
     AUDIO_StopDMA();
     AUDIO_StartDMA();
-    if (frameticker > 1)
+    audioStarted = 1;
-      frameticker = 1;
+
+    /* resynchronize emulation */
+    frameticker = 1;
   }
 }
 
@@ -150,6 +150,12 @@ void gx_audio_Start(void)
   AUDIO_RegisterDMACallback(NULL);
   DSP_Halt();
 
+  /* when not using 60hz mode, frame emulation is synchronized with Audio Interface DMA */
+  if (gc_pal | vdp_pal)
+  {
+    AUDIO_RegisterDMACallback(ai_callback);
+  }
+
   /* reset emulation audio processing */
   memset(soundbuffer, 0, 2 * 3840);
   audioStarted = 0;

source/gx/gx_video.c

@@ -1306,9 +1306,13 @@ void gx_video_Start(void)
 {
   /* 50Hz/60Hz mode */
   if ((config.tv_mode == 1) || ((config.tv_mode == 2) && vdp_pal))
+  {
     gc_pal = 1;
+  }
   else
+  {
     gc_pal = 0;
+  }
 
 #ifdef HW_RVL
   VIDEO_SetTrapFilter(config.trap);
@@ -1318,7 +1322,9 @@ void gx_video_Start(void)
   /* VSYNC callbacks */
   /* in 60hz mode, frame emulation is synchronized with Video Interrupt */
   if (!gc_pal && !vdp_pal)
+  {
     VIDEO_SetPreRetraceCallback(vi_callback);
+  }
   VIDEO_SetPostRetraceCallback(NULL);
   VIDEO_Flush();
 
@@ -1342,9 +1348,13 @@ void gx_video_Start(void)
   {
     /* allocate filters */
     if (!sms_ntsc)
+    {
       sms_ntsc = (sms_ntsc_t *)memalign(32,sizeof(sms_ntsc_t));
+    }
     if (!md_ntsc)
+    {
       md_ntsc = (md_ntsc_t *)memalign(32,sizeof(md_ntsc_t));
+    }
 
     /* setup filters default configuration */
     switch (config.ntsc)
@@ -1366,9 +1376,13 @@ void gx_video_Start(void)
 
   /* lightgun textures */
   if (config.gun_cursor[0] && (input.dev[4] == DEVICE_LIGHTGUN))
+  {
     crosshair[0] = gxTextureOpenPNG(Crosshair_p1_png,0);
+  }
   if (config.gun_cursor[1] && (input.dev[5] == DEVICE_LIGHTGUN))
+  {
     crosshair[1] = gxTextureOpenPNG(Crosshair_p2_png,0);
+  }
 
   /* GX emulation rendering */
   gxResetRendering(0);
@@ -1382,7 +1396,7 @@ void gx_video_Update(void)
 {
   int update = bitmap.viewport.changed & 1;
 
-  /* check if display has changed */
+  /* check if display has changed during frame */
   if (update)
   {
     /* update texture size */
@@ -1391,11 +1405,15 @@ void gx_video_Update(void)
 
     /* interlaced mode */
     if (config.render && interlaced)
+    {
       vheight = vheight << 1;
+    }
 
     /* ntsc filter */
     if (config.ntsc)
+    {
       vwidth = (reg[12] & 1) ? MD_NTSC_OUT_WIDTH(vwidth) : SMS_NTSC_OUT_WIDTH(vwidth);
+    }
 
     /* texels size must be multiple of 4 */
     vwidth  = (vwidth  >> 2) << 2;
@@ -1407,16 +1425,22 @@ void gx_video_Update(void)
 
     /* 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 TV mode */
+    /* update rendering mode */
     if (config.render)
+    {
       rmode = tvmodes[gc_pal*3 + 2];
+    }
     else
+    {
       rmode = tvmodes[gc_pal*3 + interlaced];
+    }
 
     /* update aspect ratio */
     gxResetScaler(vwidth);
@@ -1426,7 +1450,6 @@ void gx_video_Update(void)
 
     /* update VI mode */
     VIDEO_Configure(rmode);
-    VIDEO_Flush();
   }
 
   /* texture is now directly mapped by the line renderer */
@@ -1438,37 +1461,46 @@ void gx_video_Update(void)
   /* render textured quad */
   draw_square();
 
-  /* LightGun marks */
+  /* Lightgun marks */
   if (crosshair[0])
+  {
     gxDrawCrosshair(crosshair[0], input.analog[0][0],input.analog[0][1]);
+  }
   if (crosshair[1])
+  {
     gxDrawCrosshair(crosshair[1], input.analog[1][0],input.analog[1][1]);
+  }
 
-  /* swap XFB */
+  /* swap XFB */ 
   whichfb ^= 1;
 
   /* copy EFB to XFB */
   GX_DrawDone();
   GX_CopyDisp(xfb[whichfb], GX_TRUE);
   GX_Flush();
+
+  /* XFB is ready to be displayed */
   VIDEO_SetNextFramebuffer(xfb[whichfb]);
   VIDEO_Flush();
 
   if (update)
   {
+    /* Clear update flags */
+    bitmap.viewport.changed &= ~1;
+
     /* field synchronization */
     VIDEO_WaitVSync();
     if (rmode->viTVMode & VI_NON_INTERLACE)
+    {
       VIDEO_WaitVSync();
+    }
     else while (VIDEO_GetNextField() != odd_frame)
+    {
       VIDEO_WaitVSync();
-    if (frameticker > 1)
+    }
-      frameticker = 1;
 
-    /* force audio DMA resynchronization */
+    /* audio & video resynchronization */
     audioStarted = 0;
-
-    bitmap.viewport.changed &= ~1;
   }
 }
 

source/gx/main.c

@@ -105,7 +105,7 @@ static bool FindIOS(u32 ios)
  ***************************************************************************/
 static void load_bios(void)
 {
-  /* reset BIOS flag */
+  /* clear BIOS detection flag */
   config.tmss &= ~2;
 
   /* open BIOS file */
@@ -116,8 +116,12 @@ static void load_bios(void)
   fread(bios_rom, 1, 0x800, fp);
   fclose(fp);
 
-  /* update BIOS flags */
+  /* check ROM file */
-  config.tmss |= 2;
+  if (!strncmp((char *)(bios_rom + 0x120),"GENESIS OS", 10))
+  {
+    /* valid BIOS detected */
+    config.tmss |= 2;
+  }
 }
 
 static void init_machine(void)
@@ -173,8 +177,8 @@ static void run_emulation(void)
       ConfigRequested = 0;
 
       /* start video & audio */
-      gx_audio_Start();
       gx_video_Start();
+      gx_audio_Start();
       frameticker = 1;
     }
 
@@ -182,8 +186,8 @@ static void run_emulation(void)
     if (frameticker > 1)
     {
       /* skip frame */
-      frameticker = 0;
       system_frame(1);
+      frameticker = 1;
     }
     else
     {
@@ -198,6 +202,32 @@ static void run_emulation(void)
     /* update audio */
     gx_audio_Update();
 
+    /* check interlaced mode change */
+    if (bitmap.viewport.changed & 4)
+    {
+      /* in original 60hz modes, audio is synced with framerate */
+      if (!config.render && !vdp_pal && (config.tv_mode != 1))
+      {
+        u8 *temp = memalign(32,YM2612GetContextSize());
+        if (temp)
+        {
+          /* save YM2612 context */
+          memcpy(temp, YM2612GetContextPtr(), YM2612GetContextSize());
+
+          /* framerate has changed, reinitialize audio timings */
+          audio_init(48000, interlaced ? 59.94 : (1000000.0/16715.0));
+          sound_init();
+
+          /* restore YM2612 context */
+          YM2612Restore(temp);
+          free(temp);
+        }
+      }
+
+      /* clear flag */
+      bitmap.viewport.changed &= ~4;
+    }
+
     /* wait for next frame */
     while (frameticker < 1)
       usleep(1);
@@ -227,12 +257,8 @@ void reloadrom (int size, char *name)
   {
     /* initialize audio back-end */
     /* 60hz video mode requires synchronization with Video Interrupt.    */
-    /* VSYNC period is 16715 us on Wii/Gamecube (approx. 802.32 samples per frame) */
+    /* Framerate is 59.94 fps in interlaced/progressive modes, ~59.825 fps in non-interlaced mode */
-    float framerate;
+    float framerate = vdp_pal ? 50.0 : ((config.tv_mode == 1) ? 60.0 : (config.render ? 59.94 : (1000000.0/16715.0)));
-    if (vdp_pal)
-      framerate = 50.0;
-    else
-      framerate = ((config.tv_mode == 0) || (config.tv_mode == 2)) ? (1000000.0/16715.0) : 60.0;
     audio_init(48000, framerate);
 
     /* System Power ON */

source/sound/sn76489.c

@@ -114,7 +114,6 @@ void SN76489_Init(float PSGClockValue, int SamplingRate)
     SN76489_Context *p = &SN76489;
     p->dClock=PSGClockValue/16.0/SamplingRate;
     SN76489_Config(MUTE_ALLON, VOL_FULL, FB_SEGAVDP, SRW_SEGAVDP, config.psgBoostNoise);
-    SN76489_Reset();
 }
 
 void SN76489_Reset(void)

source/sound/sound.c

@@ -178,18 +178,21 @@ int sound_update(unsigned int cycles)
     int avail = Fir_Resampler_avail();
 
     /* resynchronize FM & PSG chips */
-    if (avail < size)
+    if (avail > size)
-    {
-      /* FM chip is late for one sample */
-      YM2612Update(Fir_Resampler_buffer(), 1);
-      Fir_Resampler_write(2);
-      fm_cycles_count += fm_cycles_ratio;
-    }
-    else
     {
       /* FM chip is ahead */
       fm_cycles_count += (avail - size) * psg_cycles_ratio;
     }
+    else
+    {
+      while (avail < size)
+      {
+        /* FM chip is late for one sample */
+        YM2612Update(Fir_Resampler_buffer(), 1);
+        Fir_Resampler_write(2);
+        avail = Fir_Resampler_avail();
+      }
+    }
   }
 
 #ifdef LOGSOUND

source/system.c

@@ -334,7 +334,7 @@ void system_frame (int do_skip)
     {
       im2_flag = ((reg[12] & 6) == 6);
       odd_frame = 1;
-      bitmap.viewport.changed = 1;
+      bitmap.viewport.changed = 5;
     }
 
     /* active screen height */