我正试图简单地提高合并视频的导出速度。
这里是代码：//从网上和SO的广泛研究中，我可以大致了解到预设的PassThrough使其变得非常快，但是正如我在代码注释中所写的那样，合并的代码没有似乎可以使用该预设进行导出：/
static func videoCompositionInstruction(_ track: AVCompositionTrack, asset: AVAsset)
-> AVMutableVideoCompositionLayerInstruction {
let instruction = AVMutableVideoCompositionLayerInstruction(assetTrack: track)
let assetTrack = asset.tracks(withMediaType: .video)[0]
let transform = assetTrack.preferredTransform
let assetInfo = orientationFromTransform(transform)
var scaleToFitRatio = 1080 / assetTrack.naturalSize.width
if assetInfo.isPortrait {
scaleToFitRatio = 1080 / assetTrack.naturalSize.height
let scaleFactor = CGAffineTransform(scaleX: scaleToFitRatio, y: scaleToFitRatio)
var finalTransform = assetTrack.preferredTransform.concatenating(scaleFactor)
//was needed in my case (if video not taking entire screen and leaving some parts black - don't know when actually needed so you'll have to try and see when it's needed)
if assetInfo.orientation == .rightMirrored || assetInfo.orientation == .leftMirrored {
finalTransform = finalTransform.translatedBy(x: -transform.ty, y: 0)
}
instruction.setTransform(finalTransform, at: CMTime.zero)
} else {
let scaleFactor = CGAffineTransform(scaleX: scaleToFitRatio, y: scaleToFitRatio)
var concat = assetTrack.preferredTransform.concatenating(scaleFactor)
.concatenating(CGAffineTransform(translationX: 0, y: UIScreen.main.bounds.width / 2))
if assetInfo.orientation == .down {
let fixUpsideDown = CGAffineTransform(rotationAngle: CGFloat(Double.pi))
let windowBounds = UIScreen.main.bounds
let yFix = assetTrack.naturalSize.height + windowBounds.height
let centerFix = CGAffineTransform(translationX: assetTrack.naturalSize.width, y: yFix)
concat = fixUpsideDown.concatenating(centerFix).concatenating(scaleFactor)
}
instruction.setTransform(concat, at: CMTime.zero)
}
return instruction
}
static func orientationFromTransform(_ transform: CGAffineTransform)
-> (orientation: UIImage.Orientation, isPortrait: Bool) {
var assetOrientation = UIImage.Orientation.up
var isPortrait = false
if transform.a == 0 && transform.b == 1.0 && transform.c == -1.0 && transform.d == 0 {
assetOrientation = .right
isPortrait = true
} else if transform.a == 0 && transform.b == 1.0 && transform.c == 1.0 && transform.d == 0 {
assetOrientation = .rightMirrored
isPortrait = true
} else if transform.a == 0 && transform.b == -1.0 && transform.c == 1.0 && transform.d == 0 {
assetOrientation = .left
isPortrait = true
} else if transform.a == 0 && transform.b == -1.0 && transform.c == -1.0 && transform.d == 0 {
assetOrientation = .leftMirrored
isPortrait = true
} else if transform.a == 1.0 && transform.b == 0 && transform.c == 0 && transform.d == 1.0 {
assetOrientation = .up
} else if transform.a == -1.0 && transform.b == 0 && transform.c == 0 && transform.d == -1.0 {
assetOrientation = .down
}
return (assetOrientation, isPortrait)
}
func mergeVideosTestSQ(arrayVideos:[AVAsset], completion:@escaping (URL?, Error?) -> ()) {
let mixComposition = AVMutableComposition()
var instructions: [AVMutableVideoCompositionLayerInstruction] = []
var insertTime = CMTime(seconds: 0, preferredTimescale: 1)
/// for each URL add the video and audio tracks and their duration to the composition
for sourceAsset in arrayVideos {
let frameRange = CMTimeRange(start: CMTime(seconds: 0, preferredTimescale: 1), duration: sourceAsset.duration)
guard
let nthVideoTrack = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)),
let nthAudioTrack = mixComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)), //0 used to be kCMPersistentTrackID_Invalid
let assetVideoTrack = sourceAsset.tracks(withMediaType: .video).first
else {
print("didnt work")
return
}
var assetAudioTrack: AVAssetTrack?
assetAudioTrack = sourceAsset.tracks(withMediaType: .audio).first
print(assetAudioTrack, ",-- assetAudioTrack???", assetAudioTrack?.asset, "<-- hes", sourceAsset)
do {
try nthVideoTrack.insertTimeRange(frameRange, of: assetVideoTrack, at: insertTime)
try nthAudioTrack.insertTimeRange(frameRange, of: assetAudioTrack!, at: insertTime)
//instructions:
let nthInstruction = MainCamVC.videoCompositionInstruction(nthVideoTrack, asset: sourceAsset)
nthInstruction.setOpacity(0.0, at: CMTimeAdd(insertTime, sourceAsset.duration)) //sourceasset.duration
instructions.append(nthInstruction)
insertTime = insertTime + sourceAsset.duration //sourceAsset.duration
} catch {
DispatchQueue.main.async {
print("didnt wor2k")
}
}
}
let mainInstruction = AVMutableVideoCompositionInstruction()
mainInstruction.timeRange = CMTimeRange(start: CMTime(seconds: 0, preferredTimescale: 1), duration: insertTime)
mainInstruction.layerInstructions = instructions
let mainComposition = AVMutableVideoComposition()
mainComposition.instructions = [mainInstruction]
mainComposition.frameDuration = CMTimeMake(value: 1, timescale: 30)
mainComposition.renderSize = CGSize(width: 1080, height: 1920)
let outputFileURL = URL(fileURLWithPath: NSTemporaryDirectory() + "merge.mp4")
//below to clear the video form docuent folder for new vid...
let fileManager = FileManager()
try? fileManager.removeItem(at: outputFileURL)
/// try to start an export session and set the path and file type
if let exportSession = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality) { //DOES NOT WORK WITH AVAssetExportPresetPassthrough
exportSession.outputFileType = .mov
exportSession.outputURL = outputFileURL
exportSession.videoComposition = mainComposition
exportSession.shouldOptimizeForNetworkUse = true
/// try to export the file and handle the status cases
exportSession.exportAsynchronously {
if let url = exportSession.outputURL{
completion(url, nil)
}
if let error = exportSession.error {
completion(nil, error)
}
}
}
}
请注意，我有说明以保持正确的方向。
感谢您的帮助！我只需要更快，它大约需要videoDuration / 2秒才能及时导出...
答案 0 :(得分：2)
将代码实现到我的项目中之后，似乎导致导出速度变慢的原因可能是处理renderSize以及视频分辨率的方式。最重要的是，使用较低的预设质量可能会提高质量。
我特别要注意这部分：
let mainInstruction = AVMutableVideoCompositionInstruction()
mainInstruction.timeRange = CMTimeRange(start: CMTime(seconds: 0, preferredTimescale: 1), duration: insertTime)
mainInstruction.layerInstructions = instructions
let mainComposition = AVMutableVideoComposition()
mainComposition.instructions = [mainInstruction]
mainComposition.frameDuration = CMTimeMake(value: 1, timescale: 30)
mainComposition.renderSize = CGSize(width: 1080, height: 1920)
将renderSize更改为= videoCompositions.size（可能与您的项目名称不同）就可以解决问题。
然后在出口处，建议更改此部分：
/// try to start an export session and set the path and file type
if let exportSession = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality) { //DOES NOT WORK WITH AVAssetExportPresetPassthrough
exportSession.outputFileType = .mov
exportSession.outputURL = outputFileURL
exportSession.videoComposition = mainComposition
exportSession.shouldOptimizeForNetworkUse = true
/// try to export the file and handle the status cases
exportSession.exportAsynchronously {
if let url = exportSession.outputURL{
completion(url, nil)
}
if let error = exportSession.error {
completion(nil, error)
}
}
}
正如我之前所说，将其更改为presetQuality低大约一个。它将大大提高速度！一些转换也被复制了，需要注意一些！