AVMutableVideoComposition: наложение статического текста ⇐ IOS

[Anonymous]

В Swift для iOS у меня есть массив AVURLAsset. Я передаю его через функцию, чтобы сшить/объединить видеоресурсы в одно окончательное видео. Моя цель — наложить текст по центру видеокадра для каждого видео.
Когда я воспроизвожу видеовыход, видеоресурсы объединяются правильно, но ни для одного из видеоресурсов не накладывается текст. . Я пытался следовать существующему ответу, но безуспешно. Я также попробовал просто наложить текст на одно видео, следуя руководству Рэя Вендерлиха, но по какой-то причине тот же конечный результат .
Любые рекомендации будут чрезвычайно признательны. ..
func merge(videos: [AVURLAsset], completion: @escaping (_ url: URL, _ asset: AVAssetExportSession)->()) {
let videoComposition = AVMutableComposition()
var lastTime: CMTime = .zero

var maxVideoSize = CGSize.zero

guard let videoCompositionTrack = videoComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)),
let audioCompositionTrack = videoComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else { return }

let mainComposition = AVMutableVideoComposition()

let mainParentLayer = CALayer()
let mainVideoLayer = CALayer()
mainParentLayer.frame = CGRect(x: 0, y: 0, width: maxVideoSize.width, height: maxVideoSize.height)
mainVideoLayer.frame = CGRect(x: 0, y: 0, width: maxVideoSize.width, height: maxVideoSize.height)

mainParentLayer.addSublayer(mainVideoLayer)

var instructions = [AVMutableVideoCompositionInstruction]()

print("Main Parent Layer Frame: \(mainParentLayer.frame)")

for video in videos {

if let videoTrack = video.tracks(withMediaType: .video)[safe: 0] {
videoCompositionTrack.preferredTransform = videoTrack.preferredTransform
print("Video Track Transform: \(videoTrack.preferredTransform)")

do {
try videoCompositionTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: video.duration), of: videoTrack, at: lastTime)
print("Video time range: Start = \(lastTime.seconds), Duration = \(video.duration.seconds) [\(lastTime.seconds + video.duration.seconds > 0 ? "Right" : "Wrong")]")

if let audioTrack = video.tracks(withMediaType: .audio)[safe: 0] {
try audioCompositionTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: video.duration), of: audioTrack, at: lastTime)
}

lastTime = CMTimeAdd(lastTime, video.duration)

let videoSize = videoTrack.naturalSize.applying(videoTrack.preferredTransform)
let videoRect = CGRect(x: 0, y: 0, width: abs(videoSize.width), height: abs(videoSize.height))
maxVideoSize = CGSize(width: max(maxVideoSize.width, videoRect.width), height: max(maxVideoSize.height, videoRect.height))

let textLayer = CATextLayer()
textLayer.string = "TESTING TESTING TESTING"
textLayer.foregroundColor = UIColor.white.cgColor
textLayer.font = UIFont(name: "Helvetica-Bold", size: min(videoRect.height / 10, 100))
textLayer.shadowOpacity = 0.5
textLayer.alignmentMode = .center
textLayer.contentsScale = UIScreen.main.scale
textLayer.isWrapped = true

let textHeight: CGFloat = min(videoRect.height / 10, 120)
let textWidth: CGFloat = videoRect.width
let xPos = (videoRect.width - textWidth) / 2
let yPos = (videoRect.height - textHeight) / 2
textLayer.frame = CGRect(x: xPos, y: yPos, width: textWidth, height: textHeight)
textLayer.zPosition = 1
print("Text Layer Frame: \(textLayer.frame) [\(textLayer.frame.width > 0 && textLayer.frame.height > 0 ? "Right" : "Wrong")]")

let parentLayer = CALayer()
parentLayer.backgroundColor = UIColor.green.cgColor // Temp background color for debugging
parentLayer.frame = videoRect
parentLayer.addSublayer(textLayer)

print("Video Layer zPosition: \(mainVideoLayer.zPosition), Text Layer zPosition: \(textLayer.zPosition) [\(textLayer.zPosition > mainVideoLayer.zPosition ? "Right" : "Wrong")]")

let videoCompositionInstruction = AVMutableVideoCompositionInstruction()
videoCompositionInstruction.timeRange = CMTimeRangeMake(start: lastTime - video.duration, duration: video.duration)
let layerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
videoCompositionInstruction.layerInstructions = [layerInstruction]
instructions.append(videoCompositionInstruction)

parentLayer.zPosition = 0
mainParentLayer.addSublayer(parentLayer)

print("Parent Layer Frame: \(parentLayer.frame), Background Color: \(parentLayer.backgroundColor.debugDescription)")
print("Text Layer Frame: \(textLayer.frame)")

} catch {
print("Failed to insert track: \(error.localizedDescription)")
return
}
}
}

mainParentLayer.frame = CGRect(x: 0, y: 0, width: maxVideoSize.width, height: maxVideoSize.height)
mainVideoLayer.frame = mainParentLayer.frame

mainComposition.renderSize = maxVideoSize
mainComposition.instructions = instructions
mainComposition.frameDuration = CMTime(value: 1, timescale: 30)
mainComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: mainVideoLayer, in: mainParentLayer)

print("Final Main Parent Layer Frame: \(mainParentLayer.frame)")
print("Number of Sublayers in Main Parent Layer: \(mainParentLayer.sublayers?.count ?? 0)")

let outputUrl = NSURL.fileURL(withPath: NSTemporaryDirectory() + "merged" + ".mp4")

print("Pre-Export Main Parent Layer Frame: \(mainParentLayer.frame)")
print("Pre-Export Number of Sublayers in Main Parent Layer: \(mainParentLayer.sublayers?.count ?? 0)")
if let sublayers = mainParentLayer.sublayers {
for (index, layer) in sublayers.enumerated() {
print("Layer \(index): \(layer), Frame: \(layer.frame), zPosition: \(layer.zPosition)")
}
}

guard let exporter = AVAssetExportSession(asset: videoComposition, presetName: AVAssetExportPresetHighestQuality) else { return }

exporter.videoComposition = mainComposition
exporter.outputURL = outputUrl
exporter.outputFileType = .mp4
exporter.shouldOptimizeForNetworkUse = true

if let videoComposition = exporter.videoComposition {
print("Export Video Composition Render Size: \(videoComposition.renderSize)")
print("Export Video Composition Frame Duration: \(videoComposition.frameDuration)")
print("Export Video Composition Instructions Count: \(videoComposition.instructions.count)")
}

exporter.exportAsynchronously {
DispatchQueue.main.async {
if let outputUrl = exporter.outputURL, exporter.status == .completed {
completion(outputUrl, exporter)
} else if let error = exporter.error {
print("Export failed: \(error.localizedDescription)")
}
}
}
play(video: exporter.asset)
}


Подробнее здесь: https://stackoverflow.com/questions/784 ... tatic-text