如何合并 2 个带有淡入淡出过渡的视频?

Question

我正在尝试两个合并 2 个重叠 2 秒的视频。在这种重叠中，我想淡入第二个视频(或淡出第一个视频以显示第二个视频，任何一个都很棒(。

第一个视频按预期在结束前 2 秒淡出，但当它淡出时，我得到一个黑屏，而不是第二个视频淡入。在视频 1 的末尾，视频 2 在动画淡入淡出的一半出现。

我看不见它们重叠的轨道做错了什么？下面是我的代码

func setupVideo() {

let url = URL(fileURLWithPath: Bundle.main.path(forResource: "demoVideoTwo", ofType: "mp4")!)
let assetOne = AVAsset(url: url)

let urlTwo = URL(fileURLWithPath: Bundle.main.path(forResource: "demoVideoThree", ofType: "mp4")!)
let assetTwo = AVAsset(url: urlTwo)

let mixComposition = AVMutableComposition()
var instructions = [AVMutableVideoCompositionLayerInstruction]()
var mainInstructionList = [AVMutableVideoCompositionInstruction]()
var lastTime = CMTime.zero

// Create Track One
guard let videoTrack = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)), let audioTrack = mixComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else {
return
}

// Setup AVAsset 1
let timeRange = CMTimeRangeMake(start: CMTime.zero, duration: assetOne.duration)

do {
try videoTrack.insertTimeRange(timeRange, of: assetOne.tracks(withMediaType: .video)[0], at: lastTime)

try audioTrack.insertTimeRange(timeRange, of: assetOne.tracks(withMediaType: .audio)[0], at: lastTime)

} catch {
print(error)
}

// Setup Layer Instruction 1
let layerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
let duration = CMTime(seconds: 2, preferredTimescale: 60)
let transitTime = CMTime(seconds: 2, preferredTimescale: 60)
let insertTime = CMTimeSubtract(assetOne.duration, transitTime)
let instRange = CMTimeRangeMake(start: insertTime, duration: duration)
layerInstruction.setOpacityRamp(fromStartOpacity: 1.0, toEndOpacity: 0.0, timeRange: instRange)
instructions.append(layerInstruction)
let mainInstruction = AVMutableVideoCompositionInstruction()
mainInstruction.timeRange = CMTimeRangeMake(start: lastTime, duration: assetOne.duration)
mainInstruction.layerInstructions = instructions
mainInstructionList.append(mainInstruction)
lastTime = CMTimeAdd(lastTime, assetOne.duration)


// Create Track One
guard let videoTrackTwo = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)), let audioTrackTwo = mixComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else {
return
}

// Setup AVAsset 2
let transitionTime = CMTime(seconds: 2, preferredTimescale: 60)
let newLastTime = CMTimeSubtract(assetOne.duration, transitionTime)
let timeRangeTwo = CMTimeRangeMake(start: CMTime.zero, duration: assetTwo.duration)
do {
try videoTrackTwo.insertTimeRange(timeRangeTwo, of: assetTwo.tracks(withMediaType: .video)[0], at: newLastTime)
try audioTrackTwo.insertTimeRange(timeRangeTwo, of: assetTwo.tracks(withMediaType: .audio)[0], at: newLastTime)
} catch {
print(error)
}


// Setup Layer Instruction 2
let layerInstructionTwo = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrackTwo)
let durationTwo = CMTime(seconds: 4, preferredTimescale: 60)
let instRangeTwo = CMTimeRangeMake(start: newLastTime, duration: durationTwo)
layerInstructionTwo.setOpacityRamp(fromStartOpacity: 0.0, toEndOpacity: 1.0, timeRange: instRangeTwo)
instructions.append(layerInstructionTwo)
let mainInstructionTwo = AVMutableVideoCompositionInstruction()
mainInstructionTwo.timeRange = CMTimeRangeMake(start: lastTime, duration: assetTwo.duration)
mainInstructionTwo.layerInstructions = instructions

mainInstructionList.append(mainInstructionTwo)

// Setup Video Composition
let mainComposition = AVMutableVideoComposition()
mainComposition.instructions = mainInstructionList
mainComposition.frameDuration = CMTimeMake(value: 1, timescale: 60)
mainComposition.renderSize = videoTrack.naturalSize

let item = AVPlayerItem(asset: mixComposition)
item.videoComposition = mainComposition

player = AVPlayer(playerItem: item)

let playerLayer: AVPlayerLayer = {
let layer = AVPlayerLayer(player: player)
layer.videoGravity = .resizeAspectFill
return layer
}()

let playerWidth: CGFloat = UIScreen.main.bounds.size.width
let videoHeight = UIScreen.main.bounds.size.width * 9 / 16

playerLayer.frame = CGRect(x: 0, y: 0, width: playerWidth, height: videoHeight)
self.layer.addSublayer(playerLayer)
}

Answer 1

不要为每个创建 AVMutableVideoCompositionInstruction 视频跟踪，并且不要每次都为其分配说明。相反，在创建AVMutableVideoComposition之前，只需创建AVMutableVideoCompositionInstructions一次，然后为其分配指令。

这是您想要的这种方式工作的代码。

func setupVideo() {
let url = URL(fileURLWithPath: Bundle.main.path(forResource: "demoVideoTwo", ofType: "mp4")!)
let assetOne = AVAsset(url: url)
let urlTwo = URL(fileURLWithPath: Bundle.main.path(forResource: "demoVideoTwo", ofType: "mp4")!)
let assetTwo = AVAsset(url: urlTwo)
let mixComposition = AVMutableComposition()
var instructions = [AVMutableVideoCompositionLayerInstruction]()
var lastTime = CMTime.zero
// Create Track One
guard let videoTrack = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)), let audioTrack = mixComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else {
return
}
// Setup AVAsset 1
let timeRange = CMTimeRangeMake(start: CMTime.zero, duration: assetOne.duration)
do {
try videoTrack.insertTimeRange(timeRange, of: assetOne.tracks(withMediaType: .video)[0], at: lastTime)
try audioTrack.insertTimeRange(timeRange, of: assetOne.tracks(withMediaType: .audio)[0], at: lastTime)
} catch {
print(error)
}
// Setup Layer Instruction 1
let layerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
let duration = CMTime(seconds: 2, preferredTimescale: 60)
let transitTime = CMTime(seconds: 2, preferredTimescale: 60)
let insertTime = CMTimeSubtract(assetOne.duration, transitTime)
let instRange = CMTimeRangeMake(start: insertTime, duration: duration)
layerInstruction.setOpacityRamp(fromStartOpacity: 1.0, toEndOpacity: 0.0, timeRange: instRange)
instructions.append(layerInstruction)
lastTime = CMTimeAdd(lastTime, assetOne.duration)

// Create Track One
guard let videoTrackTwo = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)), let audioTrackTwo = mixComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else {
return
}
// Setup AVAsset 2
let transitionTime = CMTime(seconds: 2, preferredTimescale: 60)
let newLastTime = CMTimeSubtract(assetOne.duration, transitionTime)
let timeRangeTwo = CMTimeRangeMake(start: CMTime.zero, duration: assetTwo.duration)
do {
try videoTrackTwo.insertTimeRange(timeRangeTwo, of: assetTwo.tracks(withMediaType: .video)[0], at: newLastTime)
try audioTrackTwo.insertTimeRange(timeRangeTwo, of: assetTwo.tracks(withMediaType: .audio)[0], at: newLastTime)
} catch {
print(error)
}
// Setup Layer Instruction 2
let layerInstructionTwo = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrackTwo)
layerInstructionTwo.setOpacity(1.0, at: newLastTime)
instructions.append(layerInstructionTwo)
// Setup Video Composition
let mainInstruction = AVMutableVideoCompositionInstruction()
mainInstruction.timeRange = CMTimeRangeMake(start: .zero, duration: CMTimeAdd(newLastTime, assetTwo.duration))
mainInstruction.layerInstructions = instructions
let mainComposition = AVMutableVideoComposition()
mainComposition.instructions = [mainInstruction]
mainComposition.frameDuration = CMTimeMake(value: 1, timescale: 60)
mainComposition.renderSize = videoTrack.naturalSize
let item = AVPlayerItem(asset: mixComposition)
item.videoComposition = mainComposition
player = AVPlayer(playerItem: item)
let playerLayer: AVPlayerLayer = {
let layer = AVPlayerLayer(player: player)
layer.videoGravity = .resizeAspectFill
return layer
}()
let playerWidth: CGFloat = UIScreen.main.bounds.size.width
let videoHeight = UIScreen.main.bounds.size.width * 9 / 16
playerLayer.frame = CGRect(x: 0, y: 0, width: playerWidth, height: videoHeight)
self.layer.addSublayer(playerLayer)
}