src/Audio/AudioDevice.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Runtime.InteropServices;
+using System.Threading;
 
 namespace MoonWorks.Audio
 {
@@ -26,13 +26,25 @@ namespace MoonWorks.Audio
 			}
 		}
 
-		private readonly List<WeakReference<AudioResource>> resources = new List<WeakReference<AudioResource>>();
+		private readonly HashSet<WeakReference> resources = new HashSet<WeakReference>();
-		private readonly List<WeakReference<StreamingSound>> streamingSounds = new List<WeakReference<StreamingSound>>();
+		private readonly HashSet<WeakReference> autoUpdateStreamingSoundReferences = new HashSet<WeakReference>();
+
+		private AudioTweenManager AudioTweenManager;
+
+		private const int Step = 200;
+		private TimeSpan UpdateInterval;
+		private System.Diagnostics.Stopwatch TickStopwatch = new System.Diagnostics.Stopwatch();
+		private long previousTickTime;
+		private Thread Thread;
+		private AutoResetEvent WakeSignal;
+		internal readonly object StateLock = new object();
 
 		private bool IsDisposed;
 
 		public unsafe AudioDevice()
 		{
+			UpdateInterval = TimeSpan.FromTicks(TimeSpan.TicksPerSecond / Step);
+
 			FAudio.FAudioCreate(out var handle, 0, FAudio.FAUDIO_DEFAULT_PROCESSOR);
 			Handle = handle;
 
@@ -90,8 +102,8 @@ namespace MoonWorks.Audio
 			) != 0)
 			{
 				Logger.LogError("No mastering voice found!");
-				Handle = IntPtr.Zero;
 				FAudio.FAudio_Release(Handle);
+				Handle = IntPtr.Zero;
 				return;
 			}
 
@@ -105,22 +117,52 @@ namespace MoonWorks.Audio
 				SpeedOfSound,
 				Handle3D
 			);
+
+			AudioTweenManager = new AudioTweenManager();
+
+			Logger.LogInfo("Setting up audio thread...");
+			WakeSignal = new AutoResetEvent(true);
+
+			Thread = new Thread(ThreadMain);
+			Thread.IsBackground = true;
+			Thread.Start();
+
+			TickStopwatch.Start();
+			previousTickTime = 0;
 		}
 
-		internal void Update()
+		private void ThreadMain()
 		{
-			for (var i = streamingSounds.Count - 1; i >= 0; i--)
+			while (!IsDisposed)
 			{
-				var weakReference = streamingSounds[i];
+				lock (StateLock)
-				if (weakReference.TryGetTarget(out var streamingSound))
+				{
+					ThreadMainTick();
+				}
+
+				WakeSignal.WaitOne(UpdateInterval);
+			}
+		}
+
+		private void ThreadMainTick()
+		{
+			long tickDelta = TickStopwatch.Elapsed.Ticks - previousTickTime;
+			previousTickTime = TickStopwatch.Elapsed.Ticks;
+			float elapsedSeconds = (float) tickDelta / System.TimeSpan.TicksPerSecond;
+
+			foreach (var weakReference in autoUpdateStreamingSoundReferences)
+			{
+				if (weakReference.Target is StreamingSound streamingSound)
 				{
 					streamingSound.Update();
 				}
 				else
 				{
-					streamingSounds.RemoveAt(i);
+					autoUpdateStreamingSoundReferences.Remove(weakReference);
 				}
 			}
+
+			AudioTweenManager.Update(elapsedSeconds);
 		}
 
 		public void SyncPlay()
@@ -128,40 +170,95 @@ namespace MoonWorks.Audio
 			FAudio.FAudio_CommitChanges(Handle, 1);
 		}
 
-		internal void AddDynamicSoundInstance(StreamingSound instance)
+		internal void CreateTween(
+			SoundInstance soundInstance,
+			AudioTweenProperty property,
+			System.Func<float, float> easingFunction,
+			float start,
+			float end,
+			float duration,
+			float delayTime
+		) {
+			lock (StateLock)
 			{
-			streamingSounds.Add(new WeakReference<StreamingSound>(instance));
+				AudioTweenManager.CreateTween(
-		}
+					soundInstance,
-
+					property,
-		internal void AddResourceReference(WeakReference<AudioResource> resourceReference)
+					easingFunction,
-		{
+					start,
-			lock (resources)
+					end,
-			{
+					duration,
-				resources.Add(resourceReference);
+					delayTime
+				);
 			}
 		}
 
-		internal void RemoveResourceReference(WeakReference<AudioResource> resourceReference)
+		internal void ClearTweens(
+			WeakReference soundReference,
+			AudioTweenProperty property
+		) {
+			lock (StateLock)
 			{
-			lock (resources)
+				AudioTweenManager.ClearTweens(soundReference, property);
-			{
-				resources.Remove(resourceReference);
 			}
 		}
 
+		internal void WakeThread()
+		{
+			WakeSignal.Set();
+		}
+
+		internal void AddResourceReference(AudioResource resource)
+		{
+			lock (StateLock)
+			{
+				resources.Add(resource.weakReference);
+
+				if (resource is StreamingSound streamingSound && streamingSound.AutoUpdate)
+				{
+					AddAutoUpdateStreamingSoundInstance(streamingSound);
+				}
+			}
+		}
+
+		internal void RemoveResourceReference(AudioResource resource)
+		{
+			lock (StateLock)
+			{
+				resources.Remove(resource.weakReference);
+
+				if (resource is StreamingSound streamingSound && streamingSound.AutoUpdate)
+				{
+					RemoveAutoUpdateStreamingSoundInstance(streamingSound);
+				}
+			}
+		}
+
+		private void AddAutoUpdateStreamingSoundInstance(StreamingSound instance)
+		{
+			autoUpdateStreamingSoundReferences.Add(instance.weakReference);
+		}
+
+		private void RemoveAutoUpdateStreamingSoundInstance(StreamingSound instance)
+		{
+			autoUpdateStreamingSoundReferences.Remove(instance.weakReference);
+		}
+
 		protected virtual void Dispose(bool disposing)
 		{
 			if (!IsDisposed)
+			{
+				lock (StateLock)
 				{
 					if (disposing)
 					{
-					for (var i = resources.Count - 1; i >= 0; i--)
+						foreach (var weakReference in resources)
 						{
-						var weakReference = resources[i];
+							var target = weakReference.Target;
 
-						if (weakReference.TryGetTarget(out var resource))
+							if (target != null)
 							{
-							resource.Dispose();
+								(target as IDisposable).Dispose();
 							}
 						}
 						resources.Clear();
@@ -173,8 +270,8 @@ namespace MoonWorks.Audio
 					IsDisposed = true;
 				}
 			}
+		}
 
-		// TODO: override finalizer only if 'Dispose(bool disposing)' has code to free unmanaged resources
 		~AudioDevice()
 		{
 			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method

src/Audio/AudioResource.cs

@@ -8,14 +8,14 @@ namespace MoonWorks.Audio
 
 		public bool IsDisposed { get; private set; }
 
-		private WeakReference<AudioResource> selfReference;
+		internal WeakReference weakReference;
 
 		public AudioResource(AudioDevice device)
 		{
 			Device = device;
 
-			selfReference = new WeakReference<AudioResource>(this);
+			weakReference = new WeakReference(this);
-			Device.AddResourceReference(selfReference);
+			Device.AddResourceReference(this);
 		}
 
 		protected abstract void Destroy();
@@ -26,10 +26,10 @@ namespace MoonWorks.Audio
 			{
 				Destroy();
 
-				if (selfReference != null)
+				if (weakReference != null)
 				{
-					Device.RemoveResourceReference(selfReference);
+					Device.RemoveResourceReference(this);
-					selfReference = null;
+					weakReference = null;
 				}
 
 				IsDisposed = true;

src/Audio/AudioTween.cs

@@ -0,0 +1,57 @@
+using System.Collections.Generic;
+using EasingFunction = System.Func<float, float>;
+
+namespace MoonWorks.Audio
+{
+	internal enum AudioTweenProperty
+	{
+		Pan,
+		Pitch,
+		Volume,
+		FilterFrequency,
+		Reverb
+	}
+
+	internal class AudioTween
+	{
+		public System.WeakReference SoundInstanceReference;
+		public AudioTweenProperty Property;
+		public EasingFunction EasingFunction;
+		public float Time;
+		public float StartValue;
+		public float EndValue;
+		public float DelayTime;
+		public float Duration;
+	}
+
+	internal class AudioTweenPool
+	{
+		private Queue<AudioTween> Tweens = new Queue<AudioTween>(16);
+
+		public AudioTweenPool()
+		{
+			for (int i = 0; i < 16; i += 1)
+			{
+				Tweens.Enqueue(new AudioTween());
+			}
+		}
+
+		public AudioTween Obtain()
+		{
+			if (Tweens.Count > 0)
+			{
+				var tween = Tweens.Dequeue();
+				return tween;
+			}
+			else
+			{
+				return new AudioTween();
+			}
+		}
+
+		public void Free(AudioTween tween)
+		{
+			Tweens.Enqueue(tween);
+		}
+	}
+}

src/Audio/AudioTweenManager.cs

@@ -0,0 +1,169 @@
+using System;
+using System.Collections.Generic;
+
+namespace MoonWorks.Audio
+{
+	internal class AudioTweenManager
+	{
+		private AudioTweenPool AudioTweenPool = new AudioTweenPool();
+		private readonly Dictionary<(WeakReference, AudioTweenProperty), AudioTween> AudioTweens = new Dictionary<(WeakReference, AudioTweenProperty), AudioTween>();
+		private readonly List<AudioTween> DelayedAudioTweens = new List<AudioTween>();
+
+		public void Update(float elapsedSeconds)
+		{
+			for (var i = DelayedAudioTweens.Count - 1; i >= 0; i--)
+			{
+				var audioTween = DelayedAudioTweens[i];
+				if (audioTween.SoundInstanceReference.Target is SoundInstance soundInstance)
+				{
+					audioTween.Time += elapsedSeconds;
+
+					if (audioTween.Time >= audioTween.DelayTime)
+					{
+						// set the tween start value to the current value of the property
+						switch (audioTween.Property)
+						{
+							case AudioTweenProperty.Pan:
+								audioTween.StartValue = soundInstance.Pan;
+								break;
+
+							case AudioTweenProperty.Pitch:
+								audioTween.StartValue = soundInstance.Pitch;
+								break;
+
+							case AudioTweenProperty.Volume:
+								audioTween.StartValue = soundInstance.Volume;
+								break;
+
+							case AudioTweenProperty.FilterFrequency:
+								audioTween.StartValue = soundInstance.FilterFrequency;
+								break;
+
+							case AudioTweenProperty.Reverb:
+								audioTween.StartValue = soundInstance.Reverb;
+								break;
+						}
+
+						audioTween.Time = 0;
+						DelayedAudioTweens.RemoveAt(i);
+
+						AddTween(audioTween);
+					}
+				}
+				else
+				{
+					AudioTweenPool.Free(audioTween);
+					DelayedAudioTweens.RemoveAt(i);
+				}
+			}
+
+			foreach (var (key, audioTween) in AudioTweens)
+			{
+				bool finished = true;
+				if (audioTween.SoundInstanceReference.Target is SoundInstance soundInstance)
+				{
+					finished = UpdateAudioTween(audioTween, soundInstance, elapsedSeconds);
+				}
+
+				if (finished)
+				{
+					AudioTweenPool.Free(audioTween);
+					AudioTweens.Remove(key);
+				}
+			}
+		}
+
+		public void CreateTween(
+			SoundInstance soundInstance,
+			AudioTweenProperty property,
+			System.Func<float, float> easingFunction,
+			float start,
+			float end,
+			float duration,
+			float delayTime
+		) {
+			var tween = AudioTweenPool.Obtain();
+			tween.SoundInstanceReference = soundInstance.weakReference;
+			tween.Property = property;
+			tween.EasingFunction = easingFunction;
+			tween.StartValue = start;
+			tween.EndValue = end;
+			tween.Duration = duration;
+			tween.Time = 0;
+			tween.DelayTime = delayTime;
+
+			if (delayTime == 0)
+			{
+				AddTween(tween);
+			}
+			else
+			{
+				DelayedAudioTweens.Add(tween);
+			}
+		}
+
+		public void ClearTweens(WeakReference soundReference, AudioTweenProperty property)
+		{
+			AudioTweens.Remove((soundReference, property));
+		}
+
+		private void AddTween(
+			AudioTween audioTween
+		) {
+			// if a tween with the same sound and property already exists, get rid of it
+			if (AudioTweens.TryGetValue((audioTween.SoundInstanceReference, audioTween.Property), out var currentTween))
+			{
+				AudioTweenPool.Free(currentTween);
+			}
+
+			AudioTweens[(audioTween.SoundInstanceReference, audioTween.Property)] = audioTween;
+		}
+
+		private static bool UpdateAudioTween(AudioTween audioTween, SoundInstance soundInstance, float delta)
+		{
+			float value;
+			audioTween.Time += delta;
+
+			var finished = audioTween.Time >= audioTween.Duration;
+			if (finished)
+			{
+				value = audioTween.EndValue;
+			}
+			else
+			{
+				value = MoonWorks.Math.Easing.Interp(
+					audioTween.StartValue,
+					audioTween.EndValue,
+					audioTween.Time,
+					audioTween.Duration,
+					audioTween.EasingFunction
+				);
+			}
+
+			switch (audioTween.Property)
+			{
+				case AudioTweenProperty.Pan:
+					soundInstance.Pan = value;
+					break;
+
+				case AudioTweenProperty.Pitch:
+					soundInstance.Pitch = value;
+					break;
+
+				case AudioTweenProperty.Volume:
+					soundInstance.Volume = value;
+					break;
+
+				case AudioTweenProperty.FilterFrequency:
+					soundInstance.FilterFrequency = value;
+					break;
+
+				case AudioTweenProperty.Reverb:
+					soundInstance.Reverb = value;
+					break;
+			}
+
+			return finished;
+		}
+	}
+}

src/Audio/ReverbEffect.cs

@@ -4,14 +4,12 @@ using System.Runtime.InteropServices;
 namespace MoonWorks.Audio
 {
 	// sound instances can send their audio to this voice to add reverb
-	public unsafe class ReverbEffect : IDisposable
+	public unsafe class ReverbEffect : AudioResource
 	{
 		private IntPtr voice;
 		public IntPtr Voice => voice;
 
-		private bool disposedValue;
+		public ReverbEffect(AudioDevice audioDevice) : base(audioDevice)
-
-		public ReverbEffect(AudioDevice audioDevice)
 		{
 			/* Init reverb */
 
@@ -97,32 +95,9 @@ namespace MoonWorks.Audio
 			}
 		}
 
-		protected virtual void Dispose(bool disposing)
+		protected override void Destroy()
 		{
-			if (!disposedValue)
+			FAudio.FAudioVoice_DestroyVoice(Voice);
-			{
-				if (disposing)
-				{
-					// TODO: dispose managed state (managed objects)
-				}
-
-				FAudio.FAudioVoice_DestroyVoice(voice);
-
-				disposedValue = true;
-			}
-		}
-
-		~ReverbEffect()
-		{
-		    // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
-		    Dispose(disposing: false);
-		}
-
-		public void Dispose()
-		{
-			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
-			Dispose(disposing: true);
-			GC.SuppressFinalize(this);
 		}
 	}
 }

src/Audio/SoundInstance.cs

@@ -1,12 +1,15 @@
 using System;
 using System.Runtime.InteropServices;
+using EasingFunction = System.Func<float, float>;
 
 namespace MoonWorks.Audio
 {
 	public abstract class SoundInstance : AudioResource
 	{
 		internal IntPtr Voice;
-		internal FAudio.FAudioWaveFormatEx Format;
+
+		private FAudio.FAudioWaveFormatEx format;
+		public FAudio.FAudioWaveFormatEx Format => format;
 
 		protected FAudio.F3DAUDIO_DSP_SETTINGS dspSettings;
 
@@ -21,7 +24,10 @@ namespace MoonWorks.Audio
 		public float Pan
 		{
 			get => pan;
-			set
+			internal set
+			{
+				value = Math.MathHelper.Clamp(value, -1f, 1f);
+				if (pan != value)
 				{
 					pan = value;
 
@@ -47,28 +53,37 @@ namespace MoonWorks.Audio
 					);
 				}
 			}
+		}
 
 		private float pitch = 0;
 		public float Pitch
 		{
 			get => pitch;
-			set
+			internal set
 			{
-				pitch = Math.MathHelper.Clamp(value, -1f, 1f);
+				value = Math.MathHelper.Clamp(value, -1f, 1f);
+				if (pitch != value)
+				{
+					pitch = value;
 					UpdatePitch();
 				}
 			}
+		}
 
 		private float volume = 1;
 		public float Volume
 		{
 			get => volume;
-			set
+			internal set
+			{
+				value = Math.MathHelper.Max(0, value);
+				if (volume != value)
 				{
 					volume = value;
 					FAudio.FAudioVoice_SetVolume(Voice, volume, 0);
 				}
 			}
+		}
 
 		private const float MAX_FILTER_FREQUENCY = 1f;
 		private const float MAX_FILTER_ONEOVERQ = 1.5f;
@@ -80,12 +95,14 @@ namespace MoonWorks.Audio
 			OneOverQ = 1f
 		};
 
-		private float FilterFrequency
+		public float FilterFrequency
 		{
 			get => filterParameters.Frequency;
-			set
+			internal set
 			{
 				value = System.Math.Clamp(value, 0.01f, MAX_FILTER_FREQUENCY);
+				if (filterParameters.Frequency != value)
+				{
 					filterParameters.Frequency = value;
 
 					FAudio.FAudioVoice_SetFilterParameters(
@@ -95,13 +112,16 @@ namespace MoonWorks.Audio
 					);
 				}
 			}
+		}
 
-		private float FilterOneOverQ
+		public float FilterOneOverQ
 		{
 			get => filterParameters.OneOverQ;
-			set
+			internal set
 			{
 				value = System.Math.Clamp(value, 0.01f, MAX_FILTER_ONEOVERQ);
+				if (filterParameters.OneOverQ != value)
+				{
 					filterParameters.OneOverQ = value;
 
 					FAudio.FAudioVoice_SetFilterParameters(
@@ -111,12 +131,15 @@ namespace MoonWorks.Audio
 					);
 				}
 			}
+		}
 
 		private FilterType filterType;
 		public FilterType FilterType
 		{
 			get => filterType;
 			set
+			{
+				if (filterType != value)
 				{
 					filterType = value;
 
@@ -133,6 +156,7 @@ namespace MoonWorks.Audio
 
 						case FilterType.LowPass:
 							filterParameters.Type = FAudio.FAudioFilterType.FAudioLowPassFilter;
+							filterParameters.Frequency = 1f;
 							break;
 
 						case FilterType.BandPass:
@@ -141,6 +165,7 @@ namespace MoonWorks.Audio
 
 						case FilterType.HighPass:
 							filterParameters.Type = FAudio.FAudioFilterType.FAudioHighPassFilter;
+							filterParameters.Frequency = 0f;
 							break;
 					}
 
@@ -151,14 +176,18 @@ namespace MoonWorks.Audio
 					);
 				}
 			}
+		}
 
 		private float reverb;
 		public unsafe float Reverb
 		{
 			get => reverb;
-			set
+			internal set
 			{
 				if (ReverbEffect != null)
+				{
+					value = MathF.Max(0, value);
+					if (reverb != value)
 					{
 						reverb = value;
 
@@ -178,6 +207,7 @@ namespace MoonWorks.Audio
 							0
 						);
 					}
+				}
 
 				#if DEBUG
 				if (ReverbEffect == null)
@@ -188,7 +218,7 @@ namespace MoonWorks.Audio
 			}
 		}
 
-		public SoundInstance(
+		public unsafe SoundInstance(
 			AudioDevice device,
 			ushort formatTag,
 			ushort bitsPerSample,
@@ -197,7 +227,7 @@ namespace MoonWorks.Audio
 			uint samplesPerSecond
 		) : base(device)
 		{
-			var format = new FAudio.FAudioWaveFormatEx
+			format = new FAudio.FAudioWaveFormatEx
 			{
 				wFormatTag = formatTag,
 				wBitsPerSample = bitsPerSample,
@@ -207,12 +237,10 @@ namespace MoonWorks.Audio
 				nAvgBytesPerSec = blockAlign * samplesPerSecond
 			};
 
-			Format = format;
-
 			FAudio.FAudio_CreateSourceVoice(
 				Device.Handle,
 				out Voice,
-				ref Format,
+				ref format,
 				FAudio.FAUDIO_VOICE_USEFILTER,
 				FAudio.FAUDIO_DEFAULT_FREQ_RATIO,
 				IntPtr.Zero,
@@ -277,6 +305,91 @@ namespace MoonWorks.Audio
 			ReverbEffect = reverbEffect;
 		}
 
+		public void SetPan(float targetValue)
+		{
+			Pan = targetValue;
+			Device.ClearTweens(weakReference, AudioTweenProperty.Pan);
+		}
+
+		public void SetPan(float targetValue, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Pan, easingFunction, Pan, targetValue, duration, 0);
+		}
+
+		public void SetPan(float targetValue, float delayTime, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Pan, easingFunction, Pan, targetValue, duration, delayTime);
+		}
+
+		public void SetPitch(float targetValue)
+		{
+			Pitch = targetValue;
+			Device.ClearTweens(weakReference, AudioTweenProperty.Pitch);
+		}
+
+		public void SetPitch(float targetValue, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Pitch, easingFunction, Pan, targetValue, duration, 0);
+		}
+
+		public void SetPitch(float targetValue, float delayTime, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Pitch, easingFunction, Pan, targetValue, duration, delayTime);
+		}
+
+		public void SetVolume(float targetValue)
+		{
+			Volume = targetValue;
+			Device.ClearTweens(weakReference, AudioTweenProperty.Volume);
+		}
+
+		public void SetVolume(float targetValue, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Volume, easingFunction, Volume, targetValue, duration, 0);
+		}
+
+		public void SetVolume(float targetValue, float delayTime, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Volume, easingFunction, Volume, targetValue, duration, delayTime);
+		}
+
+		public void SetFilterFrequency(float targetValue)
+		{
+			FilterFrequency = targetValue;
+			Device.ClearTweens(weakReference, AudioTweenProperty.FilterFrequency);
+		}
+
+		public void SetFilterFrequency(float targetValue, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.FilterFrequency, easingFunction, FilterFrequency, targetValue, duration, 0);
+		}
+
+		public void SetFilterFrequency(float targetValue, float delayTime, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.FilterFrequency, easingFunction, FilterFrequency, targetValue, duration, delayTime);
+		}
+
+		public void SetFilterOneOverQ(float targetValue)
+		{
+			FilterOneOverQ = targetValue;
+		}
+
+		public void SetReverb(float targetValue)
+		{
+			Reverb = targetValue;
+			Device.ClearTweens(weakReference, AudioTweenProperty.Reverb);
+		}
+
+		public void SetReverb(float targetValue, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Reverb, easingFunction, Volume, targetValue, duration, 0);
+		}
+
+		public void SetReverb(float targetValue, float delayTime, float duration, EasingFunction easingFunction)
+		{
+			Device.CreateTween(this, AudioTweenProperty.Reverb, easingFunction, Volume, targetValue, duration, delayTime);
+		}
+
 		public abstract void Play();
 		public abstract void QueueSyncPlay();
 		public abstract void Pause();
@@ -297,14 +410,12 @@ namespace MoonWorks.Audio
 			);
 
 			dspSettings.pMatrixCoefficients = (nint) NativeMemory.Alloc(memsize);
-			unsafe
-			{
 			byte* memPtr = (byte*) dspSettings.pMatrixCoefficients;
 			for (uint i = 0; i < memsize; i += 1)
 			{
 				memPtr[i] = 0;
 			}
-			}
+
 			SetPanMatrixCoefficients();
 		}
 

src/Audio/StreamingSound.cs

@@ -10,11 +10,21 @@ namespace MoonWorks.Audio
 	/// </summary>
 	public abstract class StreamingSound : SoundInstance
 	{
+		// How big should each buffer we consume be?
+		protected abstract int BUFFER_SIZE { get; }
+
+		// Should the AudioDevice thread automatically update this class?
+		public abstract bool AutoUpdate { get; }
+
+		// Are we actively consuming buffers?
+		protected bool ConsumingBuffers = false;
+
 		private const int BUFFER_COUNT = 3;
 		private readonly IntPtr[] buffers;
 		private int nextBufferIndex = 0;
 		private uint queuedBufferCount = 0;
-		protected abstract int BUFFER_SIZE { get; }
+
+		private readonly object StateLock = new object();
 
 		public unsafe StreamingSound(
 			AudioDevice device,
@@ -25,8 +35,6 @@ namespace MoonWorks.Audio
 			uint samplesPerSecond
 		) : base(device, formatTag, bitsPerSample, blockAlign, channels, samplesPerSecond)
 		{
-			device.AddDynamicSoundInstance(this);
-
 			buffers = new IntPtr[BUFFER_COUNT];
 			for (int i = 0; i < BUFFER_COUNT; i += 1)
 			{
@@ -45,6 +53,8 @@ namespace MoonWorks.Audio
 		}
 
 		private void PlayUsingOperationSet(uint operationSet)
+		{
+			lock (StateLock)
 			{
 				if (State == SoundState.Playing)
 				{
@@ -53,40 +63,65 @@ namespace MoonWorks.Audio
 
 				State = SoundState.Playing;
 
-			Update();
+				ConsumingBuffers = true;
+				QueueBuffers();
 				FAudio.FAudioSourceVoice_Start(Voice, 0, operationSet);
 			}
+		}
 
 		public override void Pause()
+		{
+			lock (StateLock)
 			{
 				if (State == SoundState.Playing)
 				{
+					ConsumingBuffers = false;
 					FAudio.FAudioSourceVoice_Stop(Voice, 0, 0);
 					State = SoundState.Paused;
 				}
 			}
+		}
 
 		public override void Stop()
 		{
+			lock (StateLock)
+			{
+				ConsumingBuffers = false;
 				State = SoundState.Stopped;
 			}
+		}
 
 		public override void StopImmediate()
 		{
+			lock (StateLock)
+			{
+				ConsumingBuffers = false;
 				FAudio.FAudioSourceVoice_Stop(Voice, 0, 0);
 				FAudio.FAudioSourceVoice_FlushSourceBuffers(Voice);
 				ClearBuffers();
 
 				State = SoundState.Stopped;
 			}
+		}
 
 		internal unsafe void Update()
+		{
+			lock (StateLock)
+			{
+				if (!IsDisposed)
 				{
 					if (State != SoundState.Playing)
 					{
 						return;
 					}
 
+					QueueBuffers();
+				}
+			}
+		}
+
+		protected void QueueBuffers()
+		{
 			FAudio.FAudioSourceVoice_GetState(
 				Voice,
 				out var state,
@@ -95,16 +130,18 @@ namespace MoonWorks.Audio
 
 			queuedBufferCount = state.BuffersQueued;
 
-			QueueBuffers();
+			if (ConsumingBuffers)
-		}
-
-		protected void QueueBuffers()
 			{
 				for (int i = 0; i < BUFFER_COUNT - queuedBufferCount; i += 1)
 				{
 					AddBuffer();
 				}
 			}
+			else if (queuedBufferCount == 0)
+			{
+				Stop();
+			}
+		}
 
 		protected unsafe void ClearBuffers()
 		{
@@ -124,6 +161,8 @@ namespace MoonWorks.Audio
 				out bool reachedEnd
 			);
 
+			if (filledLengthInBytes > 0)
+			{
 				FAudio.FAudioBuffer buf = new FAudio.FAudioBuffer
 				{
 					AudioBytes = (uint) filledLengthInBytes,
@@ -142,19 +181,16 @@ namespace MoonWorks.Audio
 				);
 
 				queuedBufferCount += 1;
+			}
 
-			/* We have reached the end of the file, what do we do? */
 			if (reachedEnd)
 			{
+				/* We have reached the end of the data, what do we do? */
+				ConsumingBuffers = false;
 				OnReachedEnd();
 			}
 		}
 
-		protected virtual void OnReachedEnd()
-		{
-			Stop();
-		}
-
 		protected unsafe abstract void FillBuffer(
 			void* buffer,
 			int bufferLengthInBytes, /* in bytes */
@@ -162,7 +198,13 @@ namespace MoonWorks.Audio
 			out bool reachedEnd
 		);
 
+		protected abstract void OnReachedEnd();
+
 		protected unsafe override void Destroy()
+		{
+			lock (StateLock)
+			{
+				if (!IsDisposed)
 				{
 					StopImmediate();
 
@@ -173,3 +215,5 @@ namespace MoonWorks.Audio
 				}
 			}
 		}
+	}
+}

src/Audio/StreamingSoundOgg.cs

@@ -11,6 +11,7 @@ namespace MoonWorks.Audio
 		private FAudio.stb_vorbis_info Info;
 
 		protected override int BUFFER_SIZE => 32768;
+		public override bool AutoUpdate => true;
 
 		public unsafe static StreamingSoundOgg Load(AudioDevice device, string filePath)
 		{
@@ -35,7 +36,7 @@ namespace MoonWorks.Audio
 			);
 		}
 
-		internal StreamingSoundOgg(
+		internal unsafe StreamingSoundOgg(
 			AudioDevice device,
 			IntPtr fileDataPtr, // MUST BE A NATIVE MEMORY HANDLE!!
 			IntPtr vorbisHandle,
@@ -47,8 +48,7 @@ namespace MoonWorks.Audio
 			(ushort) (4 * info.channels),
 			(ushort) info.channels,
 			info.sample_rate
-		)
+		) {
-		{
 			FileDataPtr = fileDataPtr;
 			VorbisHandle = vorbisHandle;
 			Info = info;
@@ -64,8 +64,7 @@ namespace MoonWorks.Audio
 			int bufferLengthInBytes,
 			out int filledLengthInBytes,
 			out bool reachedEnd
-		)
+		) {
-		{
 			var lengthInFloats = bufferLengthInBytes / sizeof(float);
 
 			/* NOTE: this function returns samples per channel, not total samples */
@@ -82,9 +81,14 @@ namespace MoonWorks.Audio
 		}
 
 		protected unsafe override void Destroy()
+		{
+			base.Destroy();
+
+			if (!IsDisposed)
 			{
 				FAudio.stb_vorbis_close(VorbisHandle);
 				NativeMemory.Free((void*) FileDataPtr);
 			}
 		}
 	}
+}

src/Audio/StreamingSoundSeekable.cs

@@ -14,12 +14,9 @@ namespace MoonWorks.Audio
 		{
 			if (Loop)
 			{
+				ConsumingBuffers = true;
 				Seek(0);
 			}
-			else
-			{
-				Stop();
-			}
 		}
 	}
 }

src/Game.cs

@@ -168,9 +168,8 @@ namespace MoonWorks
 				while (accumulatedUpdateTime >= Timestep)
 				{
 					Inputs.Update();
-					AudioDevice.Update();
-
 					Update(Timestep);
+					AudioDevice.WakeThread();
 
 					accumulatedUpdateTime -= Timestep;
 				}

src/Graphics/GraphicsDevice.cs

@@ -18,7 +18,7 @@ namespace MoonWorks.Graphics
 
 		public bool IsDisposed { get; private set; }
 
-		private readonly List<WeakReference<GraphicsResource>> resources = new List<WeakReference<GraphicsResource>>();
+		private readonly HashSet<WeakReference<GraphicsResource>> resources = new HashSet<WeakReference<GraphicsResource>>();
 
 		public GraphicsDevice(
 			Backend preferredBackend,
@@ -237,10 +237,9 @@ namespace MoonWorks.Graphics
 				{
 					lock (resources)
 					{
-						for (var i = resources.Count - 1; i >= 0; i--)
+						foreach (var weakReference in resources)
 						{
-							var resource = resources[i];
+							if (weakReference.TryGetTarget(out var target))
-							if (resource.TryGetTarget(out var target))
 							{
 								target.Dispose();
 							}

src/Graphics/GraphicsResource.cs

@@ -10,7 +10,7 @@ namespace MoonWorks.Graphics
 		public bool IsDisposed { get; private set; }
 		protected abstract Action<IntPtr, IntPtr> QueueDestroyFunction { get; }
 
-		private WeakReference<GraphicsResource> selfReference;
+		internal WeakReference<GraphicsResource> weakReference;
 
 		public GraphicsResource(GraphicsDevice device, bool trackResource = true)
 		{
@@ -18,8 +18,8 @@ namespace MoonWorks.Graphics
 
 			if (trackResource)
 			{
-				selfReference = new WeakReference<GraphicsResource>(this);
+				weakReference = new WeakReference<GraphicsResource>(this);
-				Device.AddResourceReference(selfReference);
+				Device.AddResourceReference(weakReference);
 			}
 		}
 
@@ -27,11 +27,11 @@ namespace MoonWorks.Graphics
 		{
 			if (!IsDisposed)
 			{
-				if (selfReference != null)
+				if (weakReference != null)
 				{
 					QueueDestroyFunction(Device.Handle, Handle);
-					Device.RemoveResourceReference(selfReference);
+					Device.RemoveResourceReference(weakReference);
-					selfReference = null;
+					weakReference = null;
 				}
 
 				IsDisposed = true;

src/Video/StreamingSoundTheora.cs

@@ -7,6 +7,8 @@ namespace MoonWorks.Video
 	{
 		private IntPtr VideoHandle;
 		protected override int BUFFER_SIZE => 8192;
+		// Theorafile is not thread safe, so let's update on the main thread.
+		public override bool AutoUpdate => false;
 
 		internal StreamingSoundTheora(
 			AudioDevice device,
@@ -32,6 +34,11 @@ namespace MoonWorks.Video
 		) {
 			var lengthInFloats = bufferLengthInBytes / sizeof(float);
 
+			// FIXME: this gets gnarly with theorafile being not thread safe
+			// is there some way we could just manually update in VideoPlayer
+			// instead of going through AudioDevice?
+			lock (Device.StateLock)
+			{
 				int samples = Theorafile.tf_readaudio(
 					VideoHandle,
 					(IntPtr) buffer,
@@ -42,4 +49,7 @@ namespace MoonWorks.Video
 				reachedEnd = Theorafile.tf_eos(VideoHandle) == 1;
 			}
 		}
+
+		protected override void OnReachedEnd() { }
+	}
 }

src/Video/Video.cs

@@ -27,7 +27,7 @@ namespace MoonWorks.Video
 		private int yWidth;
 		private int yHeight;
 
-		private bool disposed;
+		private bool IsDisposed;
 
 		public Video(string filename)
 		{
@@ -89,7 +89,7 @@ namespace MoonWorks.Video
 
 		protected virtual void Dispose(bool disposing)
 		{
-			if (!disposed)
+			if (!IsDisposed)
 			{
 				if (disposing)
 				{
@@ -100,7 +100,7 @@ namespace MoonWorks.Video
 				Theorafile.tf_close(ref Handle);
 				NativeMemory.Free(videoData);
 
-				disposed = true;
+				IsDisposed = true;
 			}
 		}
 

src/Video/VideoPlayer.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Diagnostics;
 using System.Runtime.InteropServices;
 using MoonWorks.Audio;
@@ -130,6 +130,8 @@ namespace MoonWorks.Video
 
 		public void Play()
 		{
+			if (Video == null) { return; }
+
 			if (State == VideoState.Playing)
 			{
 				return;
@@ -147,6 +149,8 @@ namespace MoonWorks.Video
 
 		public void Pause()
 		{
+			if (Video == null) { return; }
+
 			if (State != VideoState.Playing)
 			{
 				return;
@@ -164,6 +168,8 @@ namespace MoonWorks.Video
 
 		public void Stop()
 		{
+			if (Video == null) { return; }
+
 			if (State == VideoState.Stopped)
 			{
 				return;
@@ -172,20 +178,32 @@ namespace MoonWorks.Video
 			timer.Stop();
 			timer.Reset();
 
-			Theorafile.tf_reset(Video.Handle);
 			lastTimestamp = 0;
 			timeElapsed = 0;
 
-			if (audioStream != null)
+			DestroyAudioStream();
-			{
+
-				audioStream.StopImmediate();
+			Theorafile.tf_reset(Video.Handle);
-				audioStream.Dispose();
-				audioStream = null;
-			}
 
 			State = VideoState.Stopped;
 		}
 
+		public void Unload()
+		{
+			Stop();
+			Video = null;
+		}
+
+		public void Update()
+		{
+			if (Video == null) { return; }
+
+			if (audioStream != null)
+			{
+				audioStream.Update();
+			}
+		}
+
 		public void Render()
 		{
 			if (Video == null || State == VideoState.Stopped)
@@ -203,7 +221,8 @@ namespace MoonWorks.Video
 					Video.Handle,
 					(IntPtr) yuvData,
 					thisFrame - currentFrame
-				) == 1 || currentFrame == -1) {
+				) == 1 || currentFrame == -1)
+				{
 					UpdateRenderTexture();
 				}
 
@@ -216,12 +235,7 @@ namespace MoonWorks.Video
 				timer.Stop();
 				timer.Reset();
 
-				if (audioStream != null)
+				DestroyAudioStream();
-				{
-					audioStream.Stop();
-					audioStream.Dispose();
-					audioStream = null;
-				}
 
 				Theorafile.tf_reset(Video.Handle);
 
@@ -299,14 +313,27 @@ namespace MoonWorks.Video
 			// Grab the first bit of audio. We're trying to start the decoding ASAP.
 			if (AudioDevice != null && Theorafile.tf_hasaudio(Video.Handle) == 1)
 			{
+				DestroyAudioStream();
+
 				int channels, sampleRate;
 				Theorafile.tf_audioinfo(Video.Handle, out channels, out sampleRate);
+
 				audioStream = new StreamingSoundTheora(AudioDevice, Video.Handle, channels, (uint) sampleRate);
 			}
 
 			currentFrame = -1;
 		}
 
+		private void DestroyAudioStream()
+		{
+			if (audioStream != null)
+			{
+				audioStream.StopImmediate();
+				audioStream.Dispose();
+				audioStream = null;
+			}
+		}
+
 		protected virtual void Dispose(bool disposing)
 		{
 			if (!disposed)