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/*
See LICENSE folder for this sample’s licensing information.
Abstract:
Combines video frames and JET depth frames.
*/
import CoreMedia
import CoreVideo
import Metal
import MetalKit
class VideoMixer {
var description: String = "Video Mixer"
var isPrepared = false
private(set) var inputFormatDescription: CMFormatDescription?
private(set) var outputFormatDescription: CMFormatDescription?
private var outputPixelBufferPool: CVPixelBufferPool?
private let metalDevice = MTLCreateSystemDefaultDevice()!
private var renderPipelineState: MTLRenderPipelineState?
private var sampler: MTLSamplerState?
private var textureCache: CVMetalTextureCache!
private lazy var commandQueue: MTLCommandQueue? = {
return self.metalDevice.makeCommandQueue()
}()
private var fullRangeVertexBuffer: MTLBuffer?
var mixFactor: Float = 0.5
init() {
let vertexData: [Float] = [
-1.0, 1.0,
1.0, 1.0,
-1.0, -1.0,
1.0, -1.0
]
fullRangeVertexBuffer = metalDevice.makeBuffer(bytes: vertexData, length: vertexData.count * MemoryLayout<Float>.size, options: [])
let defaultLibrary = metalDevice.makeDefaultLibrary()!
let pipelineDescriptor = MTLRenderPipelineDescriptor()
pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
pipelineDescriptor.vertexFunction = defaultLibrary.makeFunction(name: "vertexMixer")
pipelineDescriptor.fragmentFunction = defaultLibrary.makeFunction(name: "fragmentMixer")
do {
renderPipelineState = try metalDevice.makeRenderPipelineState(descriptor: pipelineDescriptor)
} catch {
fatalError("Unable to create video mixer pipeline state. (\(error))")
}
// To determine how our textures are sampled, we create a sampler descriptor, which
// is used to ask for a sampler state object from our device.
let samplerDescriptor = MTLSamplerDescriptor()
samplerDescriptor.minFilter = .linear
samplerDescriptor.magFilter = .linear
sampler = metalDevice.makeSamplerState(descriptor: samplerDescriptor)
}
func prepare(with videoFormatDescription: CMFormatDescription, outputRetainedBufferCountHint: Int) {
reset()
(outputPixelBufferPool, _, outputFormatDescription) = allocateOutputBufferPool(with: videoFormatDescription,
outputRetainedBufferCountHint: outputRetainedBufferCountHint)
if outputPixelBufferPool == nil {
return
}
inputFormatDescription = videoFormatDescription
var metalTextureCache: CVMetalTextureCache?
if CVMetalTextureCacheCreate(kCFAllocatorDefault, nil, metalDevice, nil, &metalTextureCache) != kCVReturnSuccess {
assertionFailure("Unable to allocate video mixer texture cache")
} else {
textureCache = metalTextureCache
}
isPrepared = true
}
func reset() {
outputPixelBufferPool = nil
outputFormatDescription = nil
inputFormatDescription = nil
textureCache = nil
isPrepared = false
}
struct MixerParameters {
var mixFactor: Float
}
func mix(videoPixelBuffer: CVPixelBuffer, depthPixelBuffer: CVPixelBuffer) -> CVPixelBuffer? {
if !isPrepared {
assertionFailure("Invalid state: Not prepared")
return nil
}
var newPixelBuffer: CVPixelBuffer?
CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, outputPixelBufferPool!, &newPixelBuffer)
guard let outputPixelBuffer = newPixelBuffer else {
print("Allocation failure: Could not get pixel buffer from pool (\(self.description))")
return nil
}
guard let outputTexture = makeTextureFromCVPixelBuffer(pixelBuffer: outputPixelBuffer),
let inputTexture0 = makeTextureFromCVPixelBuffer(pixelBuffer: videoPixelBuffer),
let inputTexture1 = makeTextureFromCVPixelBuffer(pixelBuffer: depthPixelBuffer) else {
return nil
}
var parameters = MixerParameters(mixFactor: mixFactor)
let renderPassDescriptor = MTLRenderPassDescriptor()
renderPassDescriptor.colorAttachments[0].texture = outputTexture
guard let fullRangeVertexBuffer = fullRangeVertexBuffer else {
print("Failed to create Metal vertex buffer")
CVMetalTextureCacheFlush(textureCache!, 0)
return nil
}
guard let sampler = sampler else {
print("Failed to create Metal sampler")
CVMetalTextureCacheFlush(textureCache!, 0)
return nil
}
// Set up command queue, buffer, and encoder
guard let commandQueue = commandQueue,
let commandBuffer = commandQueue.makeCommandBuffer(),
let commandEncoder = commandBuffer.makeRenderCommandEncoder(descriptor: renderPassDescriptor) else {
print("Failed to create Metal command queue")
CVMetalTextureCacheFlush(textureCache!, 0)
return nil
}
commandEncoder.label = "Video Mixer"
commandEncoder.setRenderPipelineState(renderPipelineState!)
commandEncoder.setVertexBuffer(fullRangeVertexBuffer, offset: 0, index: 0)
commandEncoder.setFragmentTexture(inputTexture0, index: 0)
commandEncoder.setFragmentTexture(inputTexture1, index: 1)
commandEncoder.setFragmentSamplerState(sampler, index: 0)
commandEncoder.setFragmentBytes( UnsafeMutableRawPointer(¶meters), length: MemoryLayout<MixerParameters>.size, index: 0)
commandEncoder.drawPrimitives(type: .triangleStrip, vertexStart: 0, vertexCount: 4)
commandEncoder.endEncoding()
commandBuffer.commit()
return outputPixelBuffer
}
func makeTextureFromCVPixelBuffer(pixelBuffer: CVPixelBuffer) -> MTLTexture? {
let width = CVPixelBufferGetWidth(pixelBuffer)
let height = CVPixelBufferGetHeight(pixelBuffer)
// Create a Metal texture from the image buffer
var cvTextureOut: CVMetalTexture?
CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault, textureCache, pixelBuffer, nil, .bgra8Unorm, width, height, 0, &cvTextureOut)
guard let cvTexture = cvTextureOut, let texture = CVMetalTextureGetTexture(cvTexture) else {
print("Video mixer failed to create preview texture")
CVMetalTextureCacheFlush(textureCache, 0)
return nil
}
return texture
}
}