restructure video threading implementation

src/Video/VideoAV1.cs

@@ -11,10 +11,6 @@ namespace MoonWorks.Video
 	{
 		public string Filename { get; }
 
-		// "double buffering" so we can loop without a stutter
-		internal VideoAV1Stream StreamA { get; }
-		internal VideoAV1Stream StreamB { get; }
-
 		public int Width => width;
 		public int Height => height;
 		public double FramesPerSecond { get; set; }
@@ -67,23 +63,6 @@ namespace MoonWorks.Video
 			FramesPerSecond = framesPerSecond;
 
 			Filename = filename;
-
-			StreamA = new VideoAV1Stream(device, this);
-			StreamB = new VideoAV1Stream(device, this);
-		}
-
-		// NOTE: if you call this while a VideoPlayer is playing the stream, your program will explode
-		protected override void Dispose(bool disposing)
-		{
-			if (!IsDisposed)
-			{
-				if (disposing)
-				{
-					StreamA.Dispose();
-					StreamB.Dispose();
-				}
-			}
-			base.Dispose(disposing);
 		}
 	}
 }

src/Video/VideoAV1Stream.cs

@@ -1,8 +1,11 @@
 using System;
+using System.Collections.Concurrent;
+using System.Threading;
 using MoonWorks.Graphics;
 
 namespace MoonWorks.Video
 {
+	// Note that all public methods are async.
 	internal class VideoAV1Stream : GraphicsResource
 	{
 		public IntPtr Handle => handle;
@@ -21,20 +24,65 @@ namespace MoonWorks.Video
 
 		public bool FrameDataUpdated { get; set; }
 
-		private VideoAV1 Parent;
+		private BlockingCollection<Action> Actions = new BlockingCollection<Action>();
 
-		public VideoAV1Stream(GraphicsDevice device, VideoAV1 video) : base(device)
+		private bool Running = false;
+
+		Thread Thread;
+
+		public VideoAV1Stream(GraphicsDevice device) : base(device)
 		{
 			handle = IntPtr.Zero;
-			Parent = video;
+
+			Running = true;
+
+			Thread = new Thread(ThreadMain);
+			Thread.Start();
 		}
 
-		public void Load()
+		private void ThreadMain()
+		{
+			while (Running)
+			{
+				// block until we can take an action, then run it
+				var action = Actions.Take();
+				action.Invoke();
+			}
+
+			// shutting down...
+			while (Actions.TryTake(out var action))
+			{
+				action.Invoke();
+			}
+		}
+
+		public void Load(string filename)
+		{
+			Actions.Add(() => LoadHelper(filename));
+		}
+
+		public void Reset()
+		{
+			Actions.Add(ResetHelper);
+		}
+
+		public void ReadNextFrame()
+		{
+			Actions.Add(ReadNextFrameHelper);
+		}
+
+		public void Unload()
+		{
+			Actions.Add(UnloadHelper);
+		}
+
+		private void LoadHelper(string filename)
 		{
 			if (!Loaded)
 			{
-				if (Dav1dfile.df_fopen(Parent.Filename, out handle) == 0)
+				if (Dav1dfile.df_fopen(filename, out handle) == 0)
 				{
+					Logger.LogError("Failed to load video file: " + filename);
 					throw new Exception("Failed to load video file!");
 				}
 
@@ -42,29 +90,20 @@ namespace MoonWorks.Video
 			}
 		}
 
-		public void Unload()
+		private void ResetHelper()
 		{
 			if (Loaded)
-			{
-				Dav1dfile.df_close(handle);
-				handle = IntPtr.Zero;
-			}
-		}
-
-		public void Reset()
-		{
-			lock (this)
 			{
 				Dav1dfile.df_reset(handle);
 				ReadNextFrame();
 			}
 		}
 
-		public void ReadNextFrame()
+		private void ReadNextFrameHelper()
+		{
+			if (Loaded && !Ended)
 			{
 				lock (this)
-			{
-				if (!Ended)
 				{
 					if (Dav1dfile.df_readvideo(
 						handle,
@@ -91,11 +130,26 @@ namespace MoonWorks.Video
 			}
 		}
 
+		private void UnloadHelper()
+		{
+			if (Loaded)
+			{
+				Dav1dfile.df_close(handle);
+				handle = IntPtr.Zero;
+			}
+		}
+
 		protected override void Dispose(bool disposing)
 		{
 			if (!IsDisposed)
 			{
 				Unload();
+				Running = false;
+
+				if (disposing)
+				{
+					Thread.Join();
+				}
 			}
 			base.Dispose(disposing);
 		}

src/Video/VideoPlayer.cs

@@ -18,9 +18,9 @@ namespace MoonWorks.Video
 		private VideoAV1 Video = null;
 		private VideoAV1Stream CurrentStream = null;
 
-		private Task ReadNextFrameTask;
+		// "double buffering" so we can loop without a stutter
-		private Task ResetTask;
+		private VideoAV1Stream StreamA { get; }
-		private Task ResetSecondaryStreamTask;
+		private VideoAV1Stream StreamB { get; }
 
 		private Texture yTexture = null;
 		private Texture uTexture = null;
@@ -37,6 +37,9 @@ namespace MoonWorks.Video
 
 		public VideoPlayer(GraphicsDevice device) : base(device)
 		{
+			StreamA = new VideoAV1Stream(device);
+			StreamB = new VideoAV1Stream(device);
+
 			LinearSampler = new Sampler(device, SamplerCreateInfo.LinearClamp);
 
 			timer = new Stopwatch();
@@ -50,7 +53,7 @@ namespace MoonWorks.Video
 		{
 			if (Video != video)
 			{
-				Stop();
+				Unload();
 
 				if (RenderTexture == null)
 				{
@@ -154,7 +157,7 @@ namespace MoonWorks.Video
 			lastTimestamp = 0;
 			timeElapsed = 0;
 
-			ResetDav1dStream();
+			ResetDav1dStreams();
 
 			State = VideoState.Stopped;
 		}
@@ -164,9 +167,10 @@ namespace MoonWorks.Video
 		/// </summary>
 		public void Unload()
 		{
-			ReadNextFrameTask?.Wait();
+			if (Video == null)
-			ResetTask?.Wait();
+			{
-			ResetSecondaryStreamTask?.Wait();
+				return;
+			}
 
 			timer.Stop();
 			timer.Reset();
@@ -176,12 +180,9 @@ namespace MoonWorks.Video
 
 			State = VideoState.Stopped;
 
-			Video.StreamA.Unload();
+			StreamA.Unload();
-			Video.StreamB.Unload();
+			StreamB.Unload();
 
-			ReadNextFrameTask = null;
-			ResetTask = null;
-			ResetSecondaryStreamTask = null;
 			Video = null;
 		}
 
@@ -208,8 +209,7 @@ namespace MoonWorks.Video
 				}
 
 				currentFrame = thisFrame;
-				ReadNextFrameTask = Task.Run(CurrentStream.ReadNextFrame);
+				CurrentStream.ReadNextFrame();
-				ReadNextFrameTask.ContinueWith(HandleTaskException, TaskContinuationOptions.OnlyOnFaulted);
 			}
 
 			if (CurrentStream.Ended)
@@ -217,13 +217,12 @@ namespace MoonWorks.Video
 				timer.Stop();
 				timer.Reset();
 
-				ResetSecondaryStreamTask = Task.Run(CurrentStream.Reset);
+				CurrentStream.Reset();
-				ResetSecondaryStreamTask.ContinueWith(HandleTaskException, TaskContinuationOptions.OnlyOnFaulted);
 
 				if (Loop)
 				{
 					// Start over on the next stream!
-					CurrentStream = (CurrentStream == Video.StreamA) ? Video.StreamB : Video.StreamA;
+					CurrentStream = (CurrentStream == StreamA) ? StreamB : StreamA;
 					currentFrame = -1;
 					timer.Start();
 				}
@@ -236,13 +235,11 @@ namespace MoonWorks.Video
 
 		private void UpdateRenderTexture()
 		{
+			uint uOffset;
+			uint vOffset;
+
 			lock (CurrentStream)
 			{
-				ResetTask?.Wait();
-				ResetTask = null;
-
-				var commandBuffer = Device.AcquireCommandBuffer();
-
 				var ySpan = new Span<byte>((void*) CurrentStream.yDataHandle, (int) CurrentStream.yDataLength);
 				var uSpan = new Span<byte>((void*) CurrentStream.uDataHandle, (int) CurrentStream.uvDataLength);
 				var vSpan = new Span<byte>((void*) CurrentStream.vDataHandle, (int) CurrentStream.uvDataLength);
@@ -256,6 +253,12 @@ namespace MoonWorks.Video
 				TransferBuffer.SetData(uSpan, (uint) ySpan.Length, TransferOptions.Unsafe);
 				TransferBuffer.SetData(vSpan, (uint) (ySpan.Length + uSpan.Length), TransferOptions.Unsafe);
 
+				uOffset = (uint) ySpan.Length;
+				vOffset = (uint) (ySpan.Length + vSpan.Length);
+			}
+
+			var commandBuffer = Device.AcquireCommandBuffer();
+
 			commandBuffer.BeginCopyPass();
 
 			commandBuffer.UploadToTexture(
@@ -274,7 +277,7 @@ namespace MoonWorks.Video
 				TransferBuffer,
 				uTexture,
 				new BufferImageCopy{
-						BufferOffset = (uint) ySpan.Length,
+					BufferOffset = uOffset,
 					BufferStride = CurrentStream.uvStride,
 					BufferImageHeight = uTexture.Height
 				},
@@ -286,7 +289,7 @@ namespace MoonWorks.Video
 				vTexture,
 				new BufferImageCopy
 				{
-						BufferOffset = (uint) (ySpan.Length + uSpan.Length),
+					BufferOffset = vOffset,
 					BufferStride = CurrentStream.uvStride,
 					BufferImageHeight = vTexture.Height
 				},
@@ -312,7 +315,6 @@ namespace MoonWorks.Video
 
 			Device.Submit(commandBuffer);
 		}
-		}
 
 		private static Texture CreateRenderTexture(GraphicsDevice graphicsDevice, int width, int height)
 		{
@@ -338,35 +340,19 @@ namespace MoonWorks.Video
 
 		private void InitializeDav1dStream()
 		{
-			ReadNextFrameTask?.Wait();
+			StreamA.Load(Video.Filename);
-			ReadNextFrameTask = null;
+			StreamB.Load(Video.Filename);
 
-			ResetTask?.Wait();
+			CurrentStream = StreamA;
-			ResetTask = null;
-
-			ResetSecondaryStreamTask?.Wait();
-			ResetSecondaryStreamTask = null;
-
-			ResetTask = Task.Run(Video.StreamA.Load);
-			ResetTask.ContinueWith(HandleTaskException, TaskContinuationOptions.OnlyOnFaulted);
-			ResetSecondaryStreamTask = Task.Run(Video.StreamB.Load);
-			ResetSecondaryStreamTask.ContinueWith(HandleTaskException, TaskContinuationOptions.OnlyOnFaulted);
-
-			CurrentStream = Video.StreamA;
 			currentFrame = -1;
 		}
 
-		private void ResetDav1dStream()
+		private void ResetDav1dStreams()
 		{
-			ReadNextFrameTask?.Wait();
+			StreamA.Reset();
-			ReadNextFrameTask = null;
+			StreamB.Reset();
 
-			ResetTask = Task.Run(Video.StreamA.Reset);
+			CurrentStream = StreamA;
-			ResetTask.ContinueWith(HandleTaskException, TaskContinuationOptions.OnlyOnFaulted);
-			ResetSecondaryStreamTask = Task.Run(Video.StreamB.Reset);
-			ResetSecondaryStreamTask.ContinueWith(HandleTaskException, TaskContinuationOptions.OnlyOnFaulted);
-
-			CurrentStream = Video.StreamA;
 			currentFrame = -1;
 		}