Add Unity integration for external video tracks

Add some Unity integration of the external video tracks feature by way
of a CustomVideoSource component allowing the user to inject some custom
video feed in the WebRTC connection.

As an example application, provide a SceneVideoSource component
capturing the content rendered by a given Unity camera and streaming it
as a video feed to the remote peer.

The VideoChatDemo Unity scene is updated to add a scene capture view
showing via a MediaPlayer component the scene content captured from the
camera back-buffer.

Bug: #35

libs/Microsoft.MixedReality.WebRTC.Unity/Assets/Microsoft.MixedReality.WebRTC.Unity.Editor/CaptureCameraDrawer.cs

@@ -0,0 +1,92 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System;
+using UnityEngine;
+using UnityEditor;
+
+namespace Microsoft.MixedReality.WebRTC.Unity.Editor
+{
+    /// <summary>
+    /// Property drawer for <see cref="CaptureCameraAttribute"/>, to report an error to the user if
+    /// the associated <see xref="UnityEngine.Camera"/> property instance cannot be used for framebuffer
+    /// capture by <see cref="SceneVideoSource"/>.
+    /// </summary>
+    [CustomPropertyDrawer(typeof(CaptureCameraAttribute))]
+    public class CaptureCameraDrawer : PropertyDrawer
+    {
+        private const int c_errorMessageHeight = 42;
+
+        public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+        {
+            try
+            {
+                Validate(property.objectReferenceValue as Camera);
+            }
+            catch (Exception ex)
+            {
+                // Display error message below the property
+                var totalHeight = position.height;
+                position.yMin = position.yMax - c_errorMessageHeight;
+                EditorGUI.HelpBox(position, ex.Message, MessageType.Warning);
+
+                // Adjust rect for the property itself
+                position.yMin = position.yMax - totalHeight;
+                position.yMax -= c_errorMessageHeight;
+            }
+
+            EditorGUI.PropertyField(position, property, label);
+        }
+
+        public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
+        {
+            float height = base.GetPropertyHeight(property, label);
+            try
+            {
+                Validate(property.objectReferenceValue as Camera);
+            }
+            catch (Exception)
+            {
+                // Add extra space for the error message
+                height += c_errorMessageHeight;
+            }
+            return height;
+        }
+
+        /// <summary>
+        /// Validate that a given <see xref="UnityEngine.Camera"/> instance can be used for framebuffer
+        /// capture by <see cref="SceneVideoSource"/> based on the current settings of the Unity Player
+        /// for the current build platform.
+        /// </summary>
+        /// <param name="camera">The camera instance to test the settings of.</param>
+        /// <exception xref="System.NotSupportedException">
+        /// The camera has settings not compatible with its use with <see cref="SceneVideoSource"/>.
+        /// </exception>
+        /// <seealso cref="CaptureCameraAttribute.Validate(Camera)"/>
+        public static void Validate(Camera camera)
+        {
+            if (PlayerSettings.virtualRealitySupported && (camera != null))
+            {
+                if (PlayerSettings.stereoRenderingPath == StereoRenderingPath.MultiPass)
+                {
+                    // Ensure camera is not rendering to both eyes in multi-pass stereo, otherwise the command buffer
+                    // is executed twice (once per eye) and will produce twice as many frames, which leads to stuttering
+                    // when playing back the video stream resulting from combining those frames.
+                    if (camera.stereoTargetEye == StereoTargetEyeMask.Both)
+                    {
+                        throw new NotSupportedException("Capture camera renders both eyes in multi-pass stereoscopic rendering. This is not" +
+                            " supported by the capture mechanism which cannot discriminate them. Set Camera.stereoTargetEye to either Left or" +
+                            " Right, or use a different rendering mode (Player Settings > XR Settings > Stereo Rendering Mode).");
+                    }
+                }
+#if !UNITY_2019_1_OR_NEWER
+                else if (PlayerSettings.stereoRenderingPath == StereoRenderingPath.Instancing)
+                {
+                    throw new NotSupportedException("Capture camera does not support single-pass instanced stereoscopic rendering before Unity 2019.1." +
+                        " Use a different stereoscopic rendering mode (Player Settings > XR Settings > Stereo Rendering Mode) or upgrade to Unity 2019.1+.");
+                }
+#endif
+            }
+        }
+    }
+}

libs/Microsoft.MixedReality.WebRTC.Unity/Assets/Microsoft.MixedReality.WebRTC.Unity.Editor/LocalVideoSourceEditor.cs

@@ -1,5 +1,5 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
-// Licensed under the MIT License. See LICENSE in the project root for license information.
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
 
 using System;
 using UnityEditor;
@@ -18,6 +18,7 @@ namespace Microsoft.MixedReality.WebRTC.Unity.Editor
     public class LocalVideoSourceEditor : UnityEditor.Editor
     {
         SerializedProperty _peerConnection;
+        SerializedProperty _trackName;
         SerializedProperty _autoStartCapture;
         SerializedProperty _preferredVideoCodec;
         SerializedProperty _enableMixedRealityCapture;
@@ -76,7 +77,8 @@ enum SdpVideoCodecs
         /// </summary>
         void OnEnable()
         {
-            _peerConnection = serializedObject.FindProperty("PeerConnection");
+            _peerConnection = serializedObject.FindProperty("PeerConnection");
+            _trackName = serializedObject.FindProperty("TrackName");
             _autoStartCapture = serializedObject.FindProperty("AutoStartCapture");
             _preferredVideoCodec = serializedObject.FindProperty("PreferredVideoCodec");
             _enableMixedRealityCapture = serializedObject.FindProperty("EnableMixedRealityCapture");
@@ -101,6 +103,7 @@ public override void OnInspectorGUI()
 
             GUILayout.Space(10);
             EditorGUILayout.PropertyField(_peerConnection);
+            EditorGUILayout.PropertyField(_trackName);
             EditorGUILayout.PropertyField(_autoAddTrack);
             EditorGUILayout.PropertyField(_autoStartCapture);
 

libs/Microsoft.MixedReality.WebRTC.Unity/Assets/Microsoft.MixedReality.WebRTC.Unity.Editor/PeerConnectionEditor.cs

@@ -1,5 +1,5 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
-// Licensed under the MIT License. See LICENSE in the project root for license information.
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
 
 //using UnityEngine;
 //using UnityEditor;

libs/Microsoft.MixedReality.WebRTC.Unity/Assets/Microsoft.MixedReality.WebRTC.Unity.Examples/NodeDssSignalerUI.cs

@@ -1,5 +1,5 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
-// Licensed under the MIT License. See LICENSE in the project root for license information.
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
 
 using UnityEngine;
 using UnityEngine.UI;