AVCustomEdit: Version 3.0, 2017-08-17

Added Swift target which renders the frames using Metal off screen rendering.

Signed-off-by: Liu Lantao <liulantao@gmail.com>

AVCustomEdit/AVCustomEdit-Swift/APLCrossDissolveRenderer.swift

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+/*
+ Copyright (C) 2017 Apple Inc. All Rights Reserved.
+ See LICENSE.txt for this sample’s licensing information
+ 
+ Abstract:
+ APLCrossDissolveRenderer subclass of APLMetalRenderer, renders the given source buffers to perform a cross
+  dissolve over the time range of the transition.
+ */
+
+import Foundation
+import CoreVideo
+import MetalKit
+
+class APLCrossDissolveRenderer: APLMetalRenderer {
+
+    /// Vertex coordinates used for drawing our geomentric primitives (triangles).
+    fileprivate let vertexArray: [Float] = [
+
+        -1.0, 1.0, 0, 1,
+        -1.0, -1.0, 0, 1,
+        1.0, -1.0, 0, 1,
+        -1.0, 1.0, 0, 1,
+        1.0, -1.0, 0, 1,
+        1.0, 1.0, 0, 1
+    ]
+
+    /// Texture coordinates used for drawing textures in the texture coordinate system.
+    fileprivate let textureCoordsArray: [Float] = [
+
+        0.0, 0.0,
+        0.0, 1.0,
+        1.0, 1.0,
+        0.0, 0.0,
+        1.0, 1.0,
+        1.0, 0.0
+    ]
+
+    /// The colors for each vertex coordinate.
+    fileprivate let colorArray: [Float] = [
+
+        1, 0, 0, 1,
+        0, 1, 0, 1,
+        0, 0, 1, 1,
+        1, 0, 0, 1,
+        0, 0, 1, 1,
+        1, 0, 1, 1
+    ]
+
+    /// MTLRenderPipelineState objects that contains compiled rendering state, including vertex and fragment shaders.
+    fileprivate var foregroundRenderPipelineState: MTLRenderPipelineState?
+    fileprivate var backgroundRenderPipelineState: MTLRenderPipelineState?
+
+    /// MTLBuffer used for vertex data.
+    fileprivate var vertexBuffer: MTLBuffer?
+    /// MTLBuffer used for texture data.
+    fileprivate var textureCoordBuffer: MTLBuffer?
+    /// MTLBuffer used for color data.
+    fileprivate var colorBuffer: MTLBuffer?
+
+    /*
+     Instance of RenderPixelBuffers to maintain references to pixel buffers until they are no longer
+     needed.
+    */
+    fileprivate var pixelBuffers: RenderPixelBuffers?
+
+    override init?() {
+
+        super.init()
+
+        // The default library contains all of the shader functions that were compiled into our app bundle.
+        guard let library = device.newDefaultLibrary() else { return nil }
+
+        // Retrieve the functions that will comprise our pipeline.
+
+        // Load the vertex program into the library
+        guard let vertexFunc = library.makeFunction(name: "passthroughVertexShader") else { return nil }
+
+        // Load the fragment program into the library
+        guard let fragmentFunc = library.makeFunction(name: "texturedQuadFragmentShader") else { return nil }
+
+        vertexBuffer =
+            device.makeBuffer(bytes: vertexArray,
+                              length: vertexArray.count * MemoryLayout.size(ofValue: vertexArray[0]),
+                              options: .storageModeShared)
+
+        textureCoordBuffer =
+            device.makeBuffer(bytes: textureCoordsArray,
+                              length: textureCoordsArray.count * MemoryLayout.size(ofValue: textureCoordsArray[0]),
+                              options: .storageModeShared)
+
+        colorBuffer =
+            device.makeBuffer(bytes: colorArray,
+                              length: colorArray.count * MemoryLayout.size(ofValue: colorArray[0]),
+                              options: .storageModeShared)
+
+        // Compile the functions and other state into a pipeline object.
+        do {
+            foregroundRenderPipelineState =
+                try buildForegroundRenderPipelineState(vertexFunc, fragmentFunction: fragmentFunc)
+
+            backgroundRenderPipelineState =
+                try buildBackgroundRenderPipelineState(vertexFunc, fragmentFunction: fragmentFunc)
+        } catch {
+            print("Unable to compile render pipeline state due to error:\(error)")
+            return nil
+        }
+    }
+
+    func setupRenderPassDescriptorForTexture(_ texture: MTLTexture) -> MTLRenderPassDescriptor {
+
+        /*
+         MTLRenderPassDescriptor contains attachments that are the rendering destination for pixels
+         generated by a rendering pass.
+        */
+        let renderPassDescriptor = MTLRenderPassDescriptor()
+
+        // Associate the texture object with the attachment.
+        renderPassDescriptor.colorAttachments[0].texture = texture
+        // Set color to use when the color attachment is cleared.
+        renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColor(red: 0, green: 0, blue: 0, alpha: 1.0)
+        renderPassDescriptor.colorAttachments[0].loadAction = .clear
+        renderPassDescriptor.colorAttachments[0].storeAction = .store
+
+        return renderPassDescriptor
+    }
+
+    func buildForegroundRenderPipelineState(_ vertexFunction: MTLFunction, fragmentFunction: MTLFunction) throws -> MTLRenderPipelineState {
+
+        // A MTLRenderPipelineDescriptor object that describes the attributes of the render pipeline state.
+        let pipelineDescriptor = MTLRenderPipelineDescriptor()
+
+        // A string to help identify this object.
+        pipelineDescriptor.label = "Render Pipeline"
+        pipelineDescriptor.vertexFunction = vertexFunction
+        pipelineDescriptor.fragmentFunction = fragmentFunction
+        // Pixel format of the color attachments texture: BGRA.
+        pipelineDescriptor.colorAttachments[0].pixelFormat = MTLPixelFormat.bgra8Unorm
+        pipelineDescriptor.colorAttachments[0].isBlendingEnabled = false
+
+        return try device.makeRenderPipelineState(descriptor: pipelineDescriptor)
+    }
+
+    func buildBackgroundRenderPipelineState(_ vertexFunction: MTLFunction, fragmentFunction: MTLFunction) throws -> MTLRenderPipelineState {
+
+        // A render pipeline descriptor describes the configuration of our programmable pipeline.
+        let pipelineDescriptor = MTLRenderPipelineDescriptor()
+
+        // A string to help identify the object.
+        pipelineDescriptor.label = "Render Pipeline - Blending"
+        // Provide the vertex and shader function and the pixel format to be used.
+        pipelineDescriptor.vertexFunction = vertexFunction
+        pipelineDescriptor.fragmentFunction = fragmentFunction
+        // Pixel format of the color attachments texture: BGRA.
+        pipelineDescriptor.colorAttachments[0].pixelFormat = MTLPixelFormat.bgra8Unorm
+
+        /*
+         Enable blending. The blend descriptor property values are then used to determine how source and
+         destination color values are combined.
+        */
+        pipelineDescriptor.colorAttachments[0].isBlendingEnabled = true
+
+        // Specify custom blend operations to perform the cross dissolve effect.
+
+        // Add portions of both source and destination pixel values.
+        pipelineDescriptor.colorAttachments[0].rgbBlendOperation = .add
+        pipelineDescriptor.colorAttachments[0].alphaBlendOperation = .add
+        // Use Blend factor of one.
+        pipelineDescriptor.colorAttachments[0].sourceRGBBlendFactor = .one
+        pipelineDescriptor.colorAttachments[0].sourceAlphaBlendFactor = .one
+        // Blend factor of 1- alpha value.
+        pipelineDescriptor.colorAttachments[0].destinationRGBBlendFactor = .oneMinusBlendAlpha
+        // Blend factor of alpha.
+        pipelineDescriptor.colorAttachments[0].destinationAlphaBlendFactor = .blendAlpha
+
+        return try device.makeRenderPipelineState(descriptor: pipelineDescriptor)
+    }
+
+    func renderTexture(_ renderEncoder: MTLRenderCommandEncoder, texture: MTLTexture,
+                       pipelineState: MTLRenderPipelineState) {
+
+        // Set the current render pipeline state object.
+        renderEncoder.setRenderPipelineState(pipelineState)
+
+        // Specify vertex, color and texture buffers for the vertex shader function.
+        renderEncoder.setVertexBuffer(vertexBuffer, offset:0, at:0)
+        renderEncoder.setVertexBuffer(colorBuffer, offset:0, at:1)
+        renderEncoder.setVertexBuffer(textureCoordBuffer, offset: 0, at: 2)
+
+        // Set a texture for the fragment shader function.
+        renderEncoder.setFragmentTexture(texture, at:0)
+
+        // Tell the render context we want to draw our primitives.
+        renderEncoder.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: 6, instanceCount: 1)
+    }
+
+    override func renderPixelBuffer(_ destinationPixelBuffer: CVPixelBuffer,
+                                    usingForegroundSourceBuffer foregroundPixelBuffer: CVPixelBuffer,
+                                    andBackgroundSourceBuffer backgroundPixelBuffer: CVPixelBuffer,
+                                    forTweenFactor tween: Float) {
+
+        // Create a MTLTexture from the CVPixelBuffer.
+        guard let foregroundTexture = buildTextureForPixelBuffer(foregroundPixelBuffer) else { return }
+        guard let backgroundTexture = buildTextureForPixelBuffer(backgroundPixelBuffer) else { return }
+        guard let destinationTexture = buildTextureForPixelBuffer(destinationPixelBuffer) else { return }
+
+        /*
+         We must maintain a reference to the pixel buffer until the Metal rendering is complete. This is because the
+         'buildTextureForPixelBuffer' function above uses CVMetalTextureCacheCreateTextureFromImage to create a
+         Metal texture (CVMetalTexture) from the IOSurface that backs the CVPixelBuffer, but
+         CVMetalTextureCacheCreateTextureFromImage doesn't increment the use count of the IOSurface; only the
+         CVPixelBuffer, and the CVMTLTexture own this IOSurface. Therefore we must maintain a reference to either
+         the pixel buffer or Metal texture until the Metal rendering is done. The MTLCommandBuffer completion
+         handler below is then used to release these references.
+         */
+        pixelBuffers = RenderPixelBuffers(foregroundPixelBuffer,
+                                          backgroundTexture: backgroundPixelBuffer,
+                                          destinationTexture: destinationPixelBuffer)
+
+        // Create a new command buffer for each renderpass to the current drawable.
+        let commandBuffer = commandQueue.makeCommandBuffer()
+        commandBuffer.label = "MyCommand"
+
+        /*
+         Obtain a drawable texture for this render pass and set up the renderpass
+         descriptor for the command encoder to render into.
+         */
+        let renderPassDescriptor = setupRenderPassDescriptorForTexture(destinationTexture)
+
+        // Create a render command encoder so we can render into something.
+        let renderEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor)
+        renderEncoder.label = "MyRenderEncoder"
+
+        guard let foregroundPipelineState = foregroundRenderPipelineState else { return }
+
+        // Render foreground texture.
+        renderTexture(renderEncoder, texture: foregroundTexture,
+                      pipelineState: foregroundPipelineState)
+
+        renderEncoder.setBlendColor(red: 0, green: 0, blue: 0, alpha: tween)
+
+        guard let backgroundPipelineState = backgroundRenderPipelineState else { return }
+
+        // Render background texture.
+        renderTexture(renderEncoder, texture: backgroundTexture,
+                      pipelineState: backgroundPipelineState)
+
+        // We're done encoding commands.
+        renderEncoder.endEncoding()
+
+        // Use the command buffer completion block to release the reference to the pixel buffers.
+        commandBuffer.addCompletedHandler({ _ in
+            self.pixelBuffers = nil // Release the reference to the pixel buffers.
+        })
+
+        // Finalize rendering here & push the command buffer to the GPU.
+        commandBuffer.commit()
+    }
+}

AVCustomEdit/AVCustomEdit-Swift/APLCustomVideoCompositionInstruction.swift

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+/*
+ Copyright (C) 2017 Apple Inc. All Rights Reserved.
+ See LICENSE.txt for this sample’s licensing information
+ 
+ Abstract:
+ Custom video composition instruction class implementing AVVideoCompositionInstruction protocol.
+ */
+
+import AVFoundation
+import Foundation
+import CoreMedia
+
+class APLCustomVideoCompositionInstruction: NSObject, AVVideoCompositionInstructionProtocol {
+
+    /// ID used by subclasses to identify the foreground frame.
+    var foregroundTrackID: CMPersistentTrackID = kCMPersistentTrackID_Invalid
+    /// ID used by subclasses to identify the background frame.
+    var backgroundTrackID: CMPersistentTrackID = kCMPersistentTrackID_Invalid
+
+    /// The timeRange during which instructions will be effective.
+    var overrideTimeRange: CMTimeRange = CMTimeRange()
+    /// Indicates whether post-processing should be skipped for the duration of the instruction.
+    var overrideEnablePostProcessing = false
+
+    /// Indicates whether to avoid some duplicate processing when rendering a frame from the same source and destinatin at different times.
+    var overrideContainsTweening = false
+    /// The track IDs required to compose frames for the instruction.
+    var overrideRequiredSourceTrackIDs: [NSValue]?
+    /// Track ID of the source frame when passthrough is in effect.
+    var overridePassthroughTrackID: CMPersistentTrackID = 0
+
+    /*
+     If for the duration of the instruction, the video composition result is one of the source frames, this property
+     should return the corresponding track ID. The compositor won't be run for the duration of the instruction and
+     the proper source frame will be used instead.
+     */
+    var passthroughTrackID: CMPersistentTrackID {
+
+        get {
+            return self.overridePassthroughTrackID
+        }
+        set {
+            self.overridePassthroughTrackID = newValue
+        }
+    }
+
+    /*
+     List of video track IDs required to compose frames for this instruction. If the value of this property
+     is nil, all source tracks will be considered required for composition.
+     */
+    var requiredSourceTrackIDs: [NSValue]? {
+
+        get {
+            return self.overrideRequiredSourceTrackIDs
+        }
+
+        set {
+            self.overrideRequiredSourceTrackIDs = newValue
+        }
+    }
+
+    // Indicates the timeRange during which the instruction is effective.
+    var timeRange: CMTimeRange {
+
+        get {
+            return self.overrideTimeRange
+        }
+
+        set(newTimeRange) {
+            self.overrideTimeRange = newTimeRange
+        }
+    }
+
+    // If NO, indicates that post-processing should be skipped for the duration of this instruction.
+    var enablePostProcessing: Bool {
+
+        get {
+            return self.overrideEnablePostProcessing
+        }
+
+        set(newPostProcessing) {
+            self.overrideEnablePostProcessing = newPostProcessing
+        }
+    }
+
+    /*
+     If YES, rendering a frame from the same source buffers and the same composition instruction at 2 different
+     compositionTime may yield different output frames. If NO, 2 such compositions would yield the
+     same frame. The media pipeline may me able to avoid some duplicate processing when containsTweening is NO.
+     */
+    var containsTweening: Bool {
+
+        get {
+            return self.overrideContainsTweening
+        }
+
+        set(newContainsTweening) {
+            self.overrideContainsTweening = newContainsTweening
+        }
+    }
+
+    init(thePassthroughTrackID: CMPersistentTrackID, forTimeRange theTimeRange: CMTimeRange) {
+        super.init()
+
+        passthroughTrackID = thePassthroughTrackID
+        timeRange = theTimeRange
+
+        requiredSourceTrackIDs = [NSValue]()
+        containsTweening = false
+        enablePostProcessing = false
+    }
+
+    init(theSourceTrackIDs: [NSValue], forTimeRange theTimeRange: CMTimeRange) {
+        super.init()
+
+        requiredSourceTrackIDs = theSourceTrackIDs
+        timeRange = theTimeRange
+
+        passthroughTrackID = kCMPersistentTrackID_Invalid
+        containsTweening = true
+        enablePostProcessing = false
+    }
+
+}