AVAssetExportSession 只工作前 6 次

Question

更新了代码示例、控制台输出和信息

我正在尝试获取视频合成的总持续时间，将其除以 10，向上舍入，然后循环播放并以这些间隔拼接视频合成。

有效，但在 'currentDuration' 变为 60+ 后，它会抛出一个 "The requested URL was not found on this server."

基本上，如果它确定它需要制作 9 个剪辑，它会在前 6 个剪辑中成功，而在其他 3 个剪辑中失败。而且我的 numLoop 没有按预期工作，似乎 while 循环在 9 个剪辑中的任何一个之前完成正在尝试。

希望 help/insight 能够导出全部 9 个剪辑。

I've noticed if the video is less than 60 seconds long, it has 100% success rate. Any video I choose over 60 seconds will fails on the 7th clip.

这是我的方法：

func splitVideo(videoComposition: AVMutableVideoComposition) {


let fileManager = NSFileManager.defaultManager()
let documentsPath : String = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,.UserDomainMask,true)[0]

//grab total duration/number of splits
let exporter: AVAssetExportSession = AVAssetExportSession(asset: asset!, presetName:AVAssetExportPresetHighestQuality)!
let totalDuration = Float64(CMTimeGetSeconds(exporter.asset.duration))
let totalDurationPieces = (totalDuration/10)
var numberOfSplits=Int(ceil(Double(totalDurationPieces)))

//prepare for loop
var loopNum : Int = 0
var currentDuration : Float64 = 0
var sessionNumber = (arc4random()%1000)

let opQueue = NSOperationQueue()
    opQueue.maxConcurrentOperationCount = 1

    while loopNum < numberOfSplits {

        //new exporter
        var destinationPath: String = documentsPath + "/splitVideo-"+String(sessionNumber)
        destinationPath+="-"+String(Int(loopNum))+".mp4"

        let new_exporter = AVAssetExportSession(asset: asset!, presetName:AVAssetExportPresetHighestQuality)!

        new_exporter.outputURL = NSURL(fileURLWithPath: destinationPath as String)
        new_exporter.videoComposition = videoComposition
        new_exporter.outputFileType = AVFileTypeMPEG4
        new_exporter.shouldOptimizeForNetworkUse = false

        new_exporter.timeRange = CMTimeRangeMake(
            CMTimeMakeWithSeconds(currentDuration, framesPerSecond!),CMTimeMakeWithSeconds(Float64(10),framesPerSecond!))

        // Set up the exporter, then:
        opQueue.addOperationWithBlock { () -> Void in
            new_exporter.exportAsynchronouslyWithCompletionHandler({
                dispatch_async(dispatch_get_main_queue(),{
                    print("Exporting... \(loopNum)")
                    self.exportDidFinish(new_exporter, loopNum: loopNum)
                })
            }) // end completion handler
        } // end block



        //prepare for next loop
        loopNum = loopNum+1
        currentDuration = currentDuration+10

    if(loopNum>=numberOfSplits){
        self.allExportsDone(Int(numberOfSplits))
        }
} // end while


}

这是 exportDidFinish 方法：

func exportDidFinish(session: AVAssetExportSession, loopNum: Int) {
let outputURL: NSURL = session.outputURL!
let library: ALAssetsLibrary = ALAssetsLibrary()
if(library.videoAtPathIsCompatibleWithSavedPhotosAlbum(outputURL)) {
    library.writeVideoAtPathToSavedPhotosAlbum(outputURL, completionBlock: {(url, error) in
//done
print("Success on \(Int(loopNum))")
})
}
}

控制台输出如下：

Exporting... 9
2016-08-20 13:39:27.980 TrimVideo[4776:1576022] Video /var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-6.mp4 cannot be saved to the saved photos album: Error Domain=NSURLErrorDomain Code=-1100 "The requested URL was not found on this server." UserInfo={NSUnderlyingError=0x1457f43f0 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}, NSErrorFailingURLStringKey=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-6.mp4, NSErrorFailingURLKey=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-6.mp4, NSURL=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-6.mp4, NSLocalizedDescription=The requested URL was not found on this server.}
Exporting... 9
2016-08-20 13:39:27.984 TrimVideo[4776:1576022] Video /var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-7.mp4 cannot be saved to the saved photos album: Error Domain=NSURLErrorDomain Code=-1100 "The requested URL was not found on this server." UserInfo={NSUnderlyingError=0x1457f88c0 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}, NSErrorFailingURLStringKey=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-7.mp4, NSErrorFailingURLKey=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-7.mp4, NSURL=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-7.mp4, NSLocalizedDescription=The requested URL was not found on this server.}
Exporting... 9
2016-08-20 13:39:27.988 TrimVideo[4776:1576022] Video /var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-8.mp4 cannot be saved to the saved photos album: Error Domain=NSURLErrorDomain Code=-1100 "The requested URL was not found on this server." UserInfo={NSUnderlyingError=0x14687cb30 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}, NSErrorFailingURLStringKey=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-8.mp4, NSErrorFailingURLKey=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-8.mp4, NSURL=file:///var/mobile/Containers/Data/Application/BE125EB7-AFC4-48B5-95C3-941B420BB71F/Documents/splitVideo-972-8.mp4, NSLocalizedDescription=The requested URL was not found on this server.}
Exporting... 9
Success on 9
Exporting... 9
Success on 9
Exporting... 9
Success on 9
Exporting... 9
Success on 9
Exporting... 9

Answer 1

好的，一些消息。

ALAssetsLibrary 自 iOS 8 起已弃用，Apple 将所有人转移到照片框架来执行此操作。好消息是 AVAssetExportSession 没有被弃用。虽然您可以继续使用已弃用的 API，但最好重写 exportDidFinish 函数以使用新的 API.
splitVideo 函数中的 while 循环抛出了十个并发导出操作。老实说，这是一个猜测，但我怀疑一旦你到达剪辑 6，就会出现一些资源争用。

因此需要对其进行重新设计，使其更加友好。最好的办法是使用 NSOperationQueue 并将 maxConcurrentOperationsCount 设置为一个（即串行队列）。

类似于：

let opQueue = NSOperationQueue()
opQueue.maxConcurrentOperationsCount = 1

for loopNum in 0..<numberOfSplits {

   // Set up the exporter, then:

    opQueue.addOperationWithBlock { () -> Void in
        new_exporter.exportAsynchronouslyWithCompletionHandler({
            dispatch_async(dispatch_get_main_queue(),{
                print("Exporting... \(loopNum)")
                self.exportDidFinish(new_exporter, loopNum: loopNum)
            })
        } // end completion handler
    } // end block

} // end while

这样做的目的是确保导出操作运行一次一个，而不是一次尝试一次。如果成功，您可以尝试提高 maxConcurrentOperationsCount 以进行一些多线程处理。

AVAssetExportSession 只工作前 6 次

AVAssetExportSession only works first 6 times

ios

avmutablecomposition

cmtime

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swift