ios - 将文本字幕添加到视频轨道(在 Swift 中)失败，错误代码为 -11841

Question

一段时间以来，我一直在努力为视频添加文本字幕。我添加了一些我详细提到的链接，但它们没有帮助。

在下面的代码中，我试图为视频添加字幕。输出文件路径如下:

file:///var/mobile/Applications/03E49B29-1070-4541-B7CB-B1366732C179/Documents/output_movie.mov

此外，输入文件是通过在同一应用程序中调用 UIPickerView 记录的，位于以下临时路径中:

file:///private/var/mobile/Applications/03E49B29-1070-4541-B7CB-B1366732C179/tmp/capture/capturedvideo.MOV

我得到的错误如下，

Error:-
Domain=AVFoundationErrorDomain Code=-11841 "Operation Stopped" UserInfo=0x15ebcfb0 {NSLocalizedDescription=Operation Stopped, NSLocalizedFailureReason=The video could not be composed.}

Description:-
<AVAssetExportSession: 0x15d97c80, asset = <AVMutableComposition: 0x15d788d0 tracks = ("<AVMutableCompositionTrack: 0x15d86910 trackID = 1, mediaType = vide, editCount = 1>")>, presetName = AVAssetExportPresetHighestQuality, outputFileType = com.apple.quicktime-movie

Completed merging the video with status code 4

我使用的代码如下。我在 iPhone 4s 的 iOS 7.1.2 上运行它。

class func mergeVideoWithTheme(outputUrl: NSURL, inputVideoUrl videoUrl: NSURL!, onComplete completionHandler: ((Int) -> ())!) -> Void {

    // 1. mergeComposition adds all the AVAssets

    var mergeComposition : AVMutableComposition = AVMutableComposition()
    var trackVideo : AVMutableCompositionTrack = mergeComposition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
    //var trackAudio : AVMutableCompositionTrack = mergeComposition.addMutableTrackWithMediaType(AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())

    // 2. Add a bank for theme insertion later

    //trackVideo.insertTimeRange(range, ofTrack: VideoHelper.Static.blankTrack, atTime: kCMTimeZero, error: nil)

    // 3. Source tracks

    let sourceAsset = AVURLAsset(URL: videoUrl, options: nil)
    let sourceDuration = CMTimeRangeMake(kCMTimeZero, sourceAsset.duration)
    let vtrack: AVAssetTrack? = sourceAsset.tracksWithMediaType(AVMediaTypeVideo)[0] as? AVAssetTrack
    let atrack: AVAssetTrack? = sourceAsset.tracksWithMediaType(AVMediaTypeAudio)[0] as? AVAssetTrack

    if (vtrack == nil) {
        return
    }

    let renderWidth = vtrack?.naturalSize.width
    let renderHeight = vtrack?.naturalSize.height
    let insertTime = kCMTimeZero
    let endTime = sourceAsset.duration
    let range = sourceDuration

    // append tracks

    trackVideo.insertTimeRange(sourceDuration, ofTrack: vtrack, atTime: insertTime, error: nil)
    //if(atrack > 0){
    //    trackAudio.insertTimeRange(sourceDuration, ofTrack: atracks[0] as AVAssetTrack, atTime: insertTime, error: nil)
    //}

    // 4. Add subtitles (we call it theme)

    var themeVideoComposition : AVMutableVideoComposition = AVMutableVideoComposition(propertiesOfAsset: sourceAsset)

    // 4.1 - Create AVMutableVideoCompositionInstruction

    let mainInstruction: AVMutableVideoCompositionInstruction = AVMutableVideoCompositionInstruction()
    mainInstruction.timeRange = range

    // 4.2 - Create an AVMutableVideoCompositionLayerInstruction for the video track and fix the orientation.

    let videolayerInstruction : AVMutableVideoCompositionLayerInstruction = AVMutableVideoCompositionLayerInstruction()
    videolayerInstruction.setTransform(trackVideo.preferredTransform, atTime: insertTime)
    videolayerInstruction.setOpacity(0.0, atTime: endTime)

    // 4.3 - Add instructions

    mainInstruction.layerInstructions = NSArray(array: [videolayerInstruction])

    themeVideoComposition.renderScale = 1.0
    themeVideoComposition.renderSize = CGSizeMake(renderWidth!, renderHeight!)
    themeVideoComposition.frameDuration = CMTimeMake(1, 30)
    themeVideoComposition.instructions = NSArray(array: [mainInstruction])

    // add the theme

    // setup variables

    // add text

    let title = String("Testing this subtitle")

    var titleLayer = CATextLayer()
    titleLayer.string = title
    titleLayer.frame =  CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
    let fontName: CFStringRef = "Helvetica-Bold"
    let fontSize = CGFloat(36)
    titleLayer.font = CTFontCreateWithName(fontName, fontSize, nil)
    titleLayer.alignmentMode = kCAAlignmentCenter
    titleLayer.foregroundColor = UIColor.whiteColor().CGColor

    var backgroundLayer = CALayer()
    backgroundLayer.frame = CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
    backgroundLayer.masksToBounds = true
    backgroundLayer.addSublayer(titleLayer)

    // 2. set parent layer and video layer

    var parentLayer = CALayer()
    var videoLayer = CALayer()
    parentLayer.frame =  CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)
    videoLayer.frame =  CGRect(x: 0, y: 0, width: renderWidth!, height: renderHeight!)

    parentLayer.addSublayer(backgroundLayer)
    parentLayer.addSublayer(videoLayer)

    // 3. make animation

    themeVideoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, inLayer: parentLayer)

    // Remove the file if it already exists (merger does not overwrite)

    let fileManager = NSFileManager.defaultManager()
    fileManager.removeItemAtURL(outputUrl, error: nil)

    // export to output url

    var exporter = AVAssetExportSession(asset: mergeComposition, presetName: AVAssetExportPresetHighestQuality)
    exporter.outputURL = outputUrl
    exporter.videoComposition = themeVideoComposition
    exporter.outputFileType = AVFileTypeQuickTimeMovie
    exporter.shouldOptimizeForNetworkUse = true
    exporter.exportAsynchronouslyWithCompletionHandler({
        if (exporter.error != nil) {
            println("Error")
            println(exporter.error)
            println("Description")
            println(exporter.description)
        }
        completionHandler(exporter.status.rawValue)
    })
}

非常感谢您的帮助。我没有找到任何向视频添加动画的快速示例。想知道它是否适用于 swift 上的任何人。

引用文献:(1) https://gist.github.com/SheffieldKevin/c01789ccff2b2a87f5ea (2) http://www.raywenderlich.com/30200/avfoundation-tutorial-adding-overlays-and-animations-to-videos

Answer 1

创建图层指令时插入 trackID 失败。尝试:

let videolayerInstruction : AVMutableVideoCompositionLayerInstruction = AVMutableVideoCompositionLayerInstruction(vtrack)