realtime sound throttling. i don't think this implementation is very good, but hopefully it's a starting point. to test it, disable other forms of throttling first (vsync, frame limit).

BizHawk.MultiClient/Config.cs

@@ -251,6 +251,7 @@ namespace BizHawk.MultiClient
 		public bool SoundEnabled = true;
 		public bool MuteFrameAdvance = true;
 		public int SoundVolume = 100; //Range 0-100
+		public bool SoundThrottle = false;
 
 		// Log Window
 		public bool LogWindowSaveWindowPosition = true;

BizHawk.MultiClient/Sound.cs

@@ -130,18 +130,41 @@ namespace BizHawk.MultiClient
 			}
 
 			int samplesNeeded = SNDDXGetAudioSpace() * 2;
-			if (samplesNeeded == 0)
-				return;
+			short[] samples;
 
-			short[] samples = new short[samplesNeeded];
+			if (Global.Config.SoundThrottle)
+			{
+				if (DSoundBuffer == null) return; // can cause SNDDXGetAudioSpace() = 0
+				int samplesWanted = 2 * (int) (44100.0 / Global.Emulator.CoreOutputComm.VsyncRate);
+
+				while (samplesNeeded < samplesWanted)
+				{
+					System.Threading.Thread.Yield(); // TODO: much better sleeping
+					samplesNeeded = SNDDXGetAudioSpace() * 2;
+				}
+				samplesNeeded = samplesWanted;
+				samples = new short[samplesNeeded];
+				// no semisync
+				if (!Muted)
+					soundProvider.GetSamples(samples);
+				else
+					soundProvider.DiscardSamples();
+			}
+			else
+			{
+				if (samplesNeeded == 0)
+					return;
+				samples = new short[samplesNeeded];
+				if (soundProvider != null && Muted == false)
+				{
+					semisync.BaseSoundProvider = soundProvider;
+					semisync.GetSamples(samples);
+				}
+				else soundProvider.DiscardSamples();
+			}
+			
 			//Console.WriteLine(samplesNeeded/2);
 
-			if (soundProvider != null && Muted == false)
-			{
-				semisync.BaseSoundProvider = soundProvider;
-				semisync.GetSamples(samples);
-			}
-			else soundProvider.DiscardSamples();
 
 			int cursor = soundoffset;
 			for (int i = 0; i < samples.Length; i++)

BizHawk.MultiClient/config/SoundConfig.Designer.cs

@@ -35,6 +35,7 @@
 			this.SoundVolGroup = new System.Windows.Forms.GroupBox();
 			this.SoundVolBar = new System.Windows.Forms.TrackBar();
 			this.SoundVolNumeric = new System.Windows.Forms.NumericUpDown();
+			this.ThrottlecheckBox = new System.Windows.Forms.CheckBox();
 			this.SoundVolGroup.SuspendLayout();
 			((System.ComponentModel.ISupportInitialize)(this.SoundVolBar)).BeginInit();
 			((System.ComponentModel.ISupportInitialize)(this.SoundVolNumeric)).BeginInit();
@@ -117,6 +118,16 @@
 			this.SoundVolNumeric.TabIndex = 0;
 			this.SoundVolNumeric.ValueChanged += new System.EventHandler(this.SoundVolNumeric_ValueChanged);
 			// 
+			// ThrottlecheckBox
+			// 
+			this.ThrottlecheckBox.AutoSize = true;
+			this.ThrottlecheckBox.Location = new System.Drawing.Point(147, 58);
+			this.ThrottlecheckBox.Name = "ThrottlecheckBox";
+			this.ThrottlecheckBox.Size = new System.Drawing.Size(96, 17);
+			this.ThrottlecheckBox.TabIndex = 5;
+			this.ThrottlecheckBox.Text = "Sound Throttle";
+			this.ThrottlecheckBox.UseVisualStyleBackColor = true;
+			// 
 			// SoundConfig
 			// 
 			this.AcceptButton = this.OK;
@@ -124,6 +135,7 @@
 			this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
 			this.CancelButton = this.Cancel;
 			this.ClientSize = new System.Drawing.Size(287, 244);
+			this.Controls.Add(this.ThrottlecheckBox);
 			this.Controls.Add(this.SoundVolGroup);
 			this.Controls.Add(this.MuteFrameAdvance);
 			this.Controls.Add(this.SoundOnCheckBox);
@@ -152,5 +164,6 @@
         private System.Windows.Forms.GroupBox SoundVolGroup;
         private System.Windows.Forms.NumericUpDown SoundVolNumeric;
         private System.Windows.Forms.TrackBar SoundVolBar;
+		private System.Windows.Forms.CheckBox ThrottlecheckBox;
     }
 }

BizHawk.MultiClient/config/SoundConfig.cs

@@ -20,6 +20,7 @@ namespace BizHawk.MultiClient
 		{
 			SoundOnCheckBox.Checked = Global.Config.SoundEnabled;
 			MuteFrameAdvance.Checked = Global.Config.MuteFrameAdvance;
+			ThrottlecheckBox.Checked = Global.Config.SoundThrottle;
 			SoundVolBar.Value = Global.Config.SoundVolume;
 			SoundVolNumeric.Value = Global.Config.SoundVolume;
 			UpdateSoundDialog();
@@ -30,6 +31,7 @@ namespace BizHawk.MultiClient
 			Global.Config.SoundEnabled = SoundOnCheckBox.Checked;
 			Global.Config.MuteFrameAdvance = MuteFrameAdvance.Checked;
 			Global.Config.SoundVolume = SoundVolBar.Value;
+			Global.Config.SoundThrottle = ThrottlecheckBox.Checked;
 			Global.Sound.ChangeVolume(Global.Config.SoundVolume);
 			Global.Sound.UpdateSoundSettings();
 			Global.Sound.StartSound();
@@ -64,11 +66,13 @@ namespace BizHawk.MultiClient
 			{
 				SoundVolGroup.Enabled = true;
 				MuteFrameAdvance.Enabled = true;
+				ThrottlecheckBox.Enabled = true;
 			}
 			else
 			{
 				SoundVolGroup.Enabled = false;
 				MuteFrameAdvance.Enabled = false;
+				ThrottlecheckBox.Enabled = false;
 			}
 		}
 	}