在 AVMutableComposition 视频中的多个视频上应用 scaleTimeRange 时遇到问题

Question

我正在尝试将视频与 scaleTimeRanges 合并（以使它们慢动作或加速）；但是，它没有按预期工作。只有第一个视频具有时间范围效果...不是全部。

这项工作是在合并视频功能中完成的；这很简单...但是我不确定为什么时间范围的缩放仅适用于第一个视频而不适用于下一个视频...

这是一个测试项目，它有我当前的代码：https://github.com/meyesyesme/creationMergeProj

这是我使用的合并功能，当前已注释掉时间范围缩放（您可以取消注释以查看它不起作用）：

func mergeVideosTestSQ(arrayVideos:[VideoSegment], completion:@escaping (URL?, Error?) -> ()) {


let mixComposition = AVMutableComposition()


var instructions: [AVMutableVideoCompositionLayerInstruction] = []
var insertTime = CMTime(seconds: 0, preferredTimescale: 1)

print(arrayVideos, "<- arrayVideos")
/// for each URL add the video and audio tracks and their duration to the composition
for videoSegment in arrayVideos {
    
    let sourceAsset = AVAsset(url: videoSegment.videoURL!)
    
    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)
        
        //MY CURRENT SPEED ATTEMPT:
        let newDuration = CMTimeMultiplyByFloat64(frameRange.duration, multiplier: videoSegment.videoSpeed)
        nthVideoTrack.scaleTimeRange(frameRange, toDuration: newDuration)
        nthAudioTrack.scaleTimeRange(frameRange, toDuration: newDuration)
        
        print(insertTime.value, "<-- fiji, newdur --->", newDuration.value, "sourceasset duration--->", sourceAsset.duration.value, "frameRange.duration -->", frameRange.duration.value)
        
        //instructions:
        let nthInstruction = ViewController.videoCompositionInstruction(nthVideoTrack, asset: sourceAsset)
        nthInstruction.setOpacity(0.0, at: CMTimeAdd(insertTime, newDuration)) //sourceasset.duration
        
        instructions.append(nthInstruction)
        insertTime = insertTime + newDuration //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)

print("<now will export: ???? ????????????????????????????????????????????????????????????????????????????????????????????????????????????")


/// 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)
        }
    }
    
}

}

您会看到这种行为：第一个视频运行良好，但接下来的视频没有，并且在设置不透明度时遇到问题，等等...我尝试了不同的组合，这是最接近的组合.

我已经被困了一段时间了！

Answer 1

1. 缩放视频后，合成的持续时间会重新计算，因此您需要根据此更改附加下一部分。替换

    insertTime = insertTime + duration
   

   与

    insertTime = insertTime + newDuration
   

2. 您还需要更新 setOpacity at 值，我建议您在 insertTime 更新后移动该行并使用新值，以删除此处的重复工作

3. 当你应用比例时，它被应用到新的构图上，所以你需要使用相对范围：

    let currentRange = CMTimeRange(start: insertTime, duration: frameRange.duration)
    nthVideoTrack.scaleTimeRange(currentRange, toDuration: newDuration)
    nthAudioTrack.scaleTimeRange(currentRange, toDuration: newDuration)