AVFoundation - 视频合并，但仅播放最后的视频

Question

我有一个[AVAsset]()数组。每当我以不同的持续时间录制不同的视频时，下面的代码会将所有持续时间合并为 1 个视频，但它只会循环播放最后一个视频。

例如，视频 1 是 1 分钟，显示一只狗在遛狗，视频 2 是 1 分钟，显示一只鸟在飞翔，视频 3 是 1 分钟，显示一匹马在奔跑。该视频将合并并播放 3 分钟，但它只会显示马连续三次奔跑 1 分钟。

我哪里做错了？

var movieFileOutput = AVCaptureMovieFileOutput()
var arrayVideos = [AVAsset]()
var videoFileUrl: URL?
// button to record video
@objc func recordButtonTapped() {
// Stop recording
if movieFileOutput.isRecording {
movieFileOutput.stopRecording()
print("Stop Recording")
} else {
// Start recording
movieFileOutput.connection(with: AVMediaType.video)?.videoOrientation = videoOrientation()
movieFileOutput.maxRecordedDuration = maxRecordDuration()
videoFileUrl = URL(fileURLWithPath: videoFileLocation())
if let videoFileUrlFromCamera = videoFileUrl {
movieFileOutput.startRecording(to: videoFileUrlFromCamera, recordingDelegate: self)
}
}
}
func videoFileLocation() -> String {
return NSTemporaryDirectory().appending("videoFile.mov")
}
// button to save the merged video
@objc func saveButtonTapped() {
mergeVids()
}
// function to merge and save videos
func mergeVids() {
let mixComposition = AVMutableComposition()
let compositionVideoTrack = mixComposition.addMutableTrack(withMediaType: .video,
preferredTrackID: Int32(kCMPersistentTrackID_Invalid))
compositionVideoTrack?.preferredTransform = CGAffineTransform(rotationAngle: .pi / 2)
let soundtrackTrack = mixComposition.addMutableTrack(withMediaType: .audio,
preferredTrackID: Int32(kCMPersistentTrackID_Invalid))
var insertTime = CMTime.zero
for videoAsset in arrayVideos {
do {
try compositionVideoTrack?.insertTimeRange(CMTimeRangeMake(start: CMTime.zero,
duration: videoAsset.duration),
of: videoAsset.tracks(withMediaType: .video)[0],
at: insertTime)
try soundtrackTrack?.insertTimeRange(CMTimeRangeMake(start: CMTime.zero,
duration: videoAsset.duration),
of: videoAsset.tracks(withMediaType: .audio)[0],
at: insertTime)
insertTime = CMTimeAdd(insertTime, videoAsset.duration)
} catch let error as NSError {
print("(error.localizedDescription)")
} 
}
let outputFileURL = URL(fileURLWithPath: NSTemporaryDirectory() + "merge.mp4")
let path = outputFileURL.path
if FileManager.default.fileExists(atPath: path) {
try! FileManager.default.removeItem(atPath: path)
}
let exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)
exporter!.outputURL = outputFileURL
exporter!.outputFileType = AVFileType.mp4
exporter!.shouldOptimizeForNetworkUse = true
exporter!.exportAsynchronously { [weak self] in
let cameraVideoURL = exporter!.outputURL!
PHPhotoLibrary.shared().performChanges({
PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: cameraVideoURL)
}) { (saved, error) in
if let error = error { return }
if !saved { return }
// url is saved
self?.videoFileUrl = nil
self?.arrayVideos.removeAll()
}
}
}
// AVCaptureFileOutputRecording Delegates
func fileOutput(_ output: AVCaptureFileOutput, didStartRecordingTo fileURL: URL, from connections: [AVCaptureConnection]) {
print("+++++++++++++++Started")
print("*****Started recording: (fileURL)n")
}
func fileOutput(_ output: AVCaptureFileOutput, didFinishRecordingTo outputFileURL: URL, from connections: [AVCaptureConnection], error: Error?) {
if error == nil {
let asset = AVAsset(url: outputFileURL)
arrayVideos.append(asset)
print(arrayVideos.count)
} else {
print("Error recording movie: (error!.localizedDescription)")
}
func cleanUp() {
let path = outputFileURL.path
if FileManager.default.fileExists(atPath: path) {
do {
try FileManager.default.removeItem(atPath: path)
} catch {
print("Could not remove file at url: (outputFileURL)")
}
}
}
}
func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
print("++++++Frame Drop: (connection.description)")
}

Answer 1

感谢@alxlives测试合并功能并指出，由于他的机器上很好，问题一定出在其他地方。

问题出在这里：

func videoFileLocation() -> String {
return NSTemporaryDirectory().appending("videoFile.mov")
}

在recordButtonTapped中，当它使用上面的代码时，它一直使用相同的"videoFile.mov"扩展名：

videoFileUrl = URL(fileURLWithPath: videoFileLocation()) // <<< it gets called here every time a new video runs
if let videoFileUrlFromCamera = videoFileUrl {
movieFileOutput.startRecording(to: videoFileUrlFromCamera, recordingDelegate: self)
}

为了修复它，我需要使每个扩展都独一无二：

func videoFileLocation() -> String {
let uuid = UUID().uuidString
return NSTemporaryDirectory().appending("videoFile_(uuid).mov")
}