闭包内的while循环期间的iOS swift内存问题：AVAssetWriter

Question

我的应用程序用于从由代码生成的许多图像制作视频文件。

当我的代码完成制作图像并将其放入 myImage 时，它​​会将 isImageReady 切换为“true”。当 self.i 被 Property Observer 设置（或更改）时，它开始制作另一个图像。最后，当没有更多图像要生成时，self.iReset 设置为 'true'。

但应用程序在 while 循环期间由于内存问题而终止。我已经注释掉了实际组装视频帧的 if 语句。它仍然存在内存问题。所以我认为问题存在于 requestMediaDataWhenReadyOnQueue:usingBlock 闭包中的 while 循环中。

我不知道如何解决这个问题。请帮我。

    if videoWriter.startWriting() {
        videoWriter.startSessionAtSourceTime(kCMTimeZero)
        assert(pixelBufferAdaptor.pixelBufferPool != nil)

        let media_queue = dispatch_queue_create("mediaInputQueue", nil)
        videoWriterInput.requestMediaDataWhenReadyOnQueue(media_queue, usingBlock: { () -> Void in
            let fps: Int32 = 30
            let frameDuration = CMTimeMake(1, fps)
            var lastFrameTime:CMTime = CMTime()
            var presentationTime:CMTime = CMTime()

            while (self.iReset != true) {
                if videoWriterInput.readyForMoreMediaData && self.isImageReady {
                    lastFrameTime = CMTimeMake(Int64(self.i), fps)
                    presentationTime = self.i == 1 ? lastFrameTime : CMTimeAdd(lastFrameTime, frameDuration)

                    //commented out for tracking
                    /* if !self.appendPixelBufferForImage(self.myImage, pixelBufferAdaptor: pixelBufferAdaptor, presentationTime: presentationTime) {
                    error = NSError(
                    domain: kErrorDomain,
                    code: kFailedToAppendPixelBufferError,
                    userInfo: [
                    "description": "AVAssetWriterInputPixelBufferAdapter failed to append pixel buffer",
                    "rawError": videoWriter.error ?? "(none)"])
                    break
                    } */

                    self.isImageReady = false
                    self.i++
                }// if ..&&..
            } //while loop ends


            // Finish writing
            videoWriterInput.markAsFinished()
            videoWriter.finishWritingWithCompletionHandler { () -> Void in
                if error == nil {
                    print("Finished Making a Movie !!")
                    success(videoOutputURL)
                }
                self.videoWriter = nil
            }
        }) // requestMediaDataWhenReadyOnQueue ends
    }

Answer 1

可能为时已晚，但我遇到了与此类似的问题（循环中的图像），这让我非常头疼。我的解决方案是在解决问题的循环中放置一个自动释放池。

Answer 2

根据@C。 Carter 建议您可以使用autoreleasepool 来释放已使用的内存，如下所示：

autoreleasepool {
  /* your code */ 
}

除此之外，这是我使用UIImages 和Audio 制作电影的代码，效果很好。

func build(chosenPhotos: [UIImage], audioURL: NSURL, completion: (NSURL) -> ()) {
        showLoadingIndicator(appDel.window!.rootViewController!.view)
        let outputSize = CGSizeMake(640, 480)
        var choosenPhotos = chosenPhotos
        let fileManager = NSFileManager.defaultManager()
        let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
        guard let documentDirectory: NSURL = urls.first else {
            fatalError("documentDir Error")
        }

    let videoOutputURL = documentDirectory.URLByAppendingPathComponent("OutputVideo.mp4")
    print("Video Output URL \(videoOutputURL)")
    if NSFileManager.defaultManager().fileExistsAtPath(videoOutputURL.path!) {
        do {
            try NSFileManager.defaultManager().removeItemAtPath(videoOutputURL.path!)
        } catch {
            fatalError("Unable to delete file: \(error) : \(#function).")
        }
    }

    guard let videoWriter = try? AVAssetWriter(URL: videoOutputURL, fileType: AVFileTypeMPEG4) else {
        fatalError("AVAssetWriter error")
    }

    let outputSettings = [AVVideoCodecKey : AVVideoCodecH264, AVVideoWidthKey : NSNumber(float: Float(outputSize.width)), AVVideoHeightKey : NSNumber(float: Float(outputSize.height))]

    guard videoWriter.canApplyOutputSettings(outputSettings, forMediaType: AVMediaTypeVideo) else {
        fatalError("Negative : Can't apply the Output settings...")
    }

    let videoWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: outputSettings)
    let sourcePixelBufferAttributesDictionary = [kCVPixelBufferPixelFormatTypeKey as String : NSNumber(unsignedInt: kCVPixelFormatType_32ARGB), kCVPixelBufferWidthKey as String: NSNumber(float: Float(outputSize.width)), kCVPixelBufferHeightKey as String: NSNumber(float: Float(outputSize.height))]
    let pixelBufferAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: videoWriterInput, sourcePixelBufferAttributes: sourcePixelBufferAttributesDictionary)

    if videoWriter.canAddInput(videoWriterInput) {
        videoWriter.addInput(videoWriterInput)
    }

    if videoWriter.startWriting() {
        videoWriter.startSessionAtSourceTime(kCMTimeZero)
        assert(pixelBufferAdaptor.pixelBufferPool != nil)

        let media_queue = dispatch_queue_create("mediaInputQueue", nil)

        videoWriterInput.requestMediaDataWhenReadyOnQueue(media_queue, usingBlock: { () -> Void in
            let fps: Int32 = 1
            let frameDuration = CMTimeMake(1, fps)

            var frameCount: Int64 = 0
            var appendSucceeded = true
            while (!choosenPhotos.isEmpty) {
                if (videoWriterInput.readyForMoreMediaData) {
                    let nextPhoto = choosenPhotos.removeAtIndex(0)
                    let lastFrameTime = CMTimeMake(frameCount, fps)
                    let presentationTime = frameCount == 0 ? lastFrameTime : CMTimeAdd(lastFrameTime, frameDuration)

                    var pixelBuffer: CVPixelBuffer? = nil
                    let status: CVReturn = CVPixelBufferPoolCreatePixelBuffer(kCFAllocatorDefault, pixelBufferAdaptor.pixelBufferPool!, &pixelBuffer)

                    if let pixelBuffer = pixelBuffer where status == 0 {
                        let managedPixelBuffer = pixelBuffer

                        CVPixelBufferLockBaseAddress(managedPixelBuffer, 0)

                        let data = CVPixelBufferGetBaseAddress(managedPixelBuffer)
                        let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
                        let context = CGBitmapContextCreate(data, Int(outputSize.width), Int(outputSize.height), 8, CVPixelBufferGetBytesPerRow(managedPixelBuffer), rgbColorSpace, CGImageAlphaInfo.PremultipliedFirst.rawValue)

                        CGContextClearRect(context, CGRectMake(0, 0, CGFloat(outputSize.width), CGFloat(outputSize.height)))

                        let horizontalRatio = CGFloat(outputSize.width) / nextPhoto.size.width
                        let verticalRatio = CGFloat(outputSize.height) / nextPhoto.size.height
                        //aspectRatio = max(horizontalRatio, verticalRatio) // ScaleAspectFill
                        let aspectRatio = min(horizontalRatio, verticalRatio) // ScaleAspectFit

                        let newSize:CGSize = CGSizeMake(nextPhoto.size.width * aspectRatio, nextPhoto.size.height * aspectRatio)

                        let x = newSize.width < outputSize.width ? (outputSize.width - newSize.width) / 2 : 0
                        let y = newSize.height < outputSize.height ? (outputSize.height - newSize.height) / 2 : 0

                        CGContextDrawImage(context, CGRectMake(x, y, newSize.width, newSize.height), nextPhoto.CGImage)

                        CVPixelBufferUnlockBaseAddress(managedPixelBuffer, 0)

                        appendSucceeded = pixelBufferAdaptor.appendPixelBuffer(pixelBuffer, withPresentationTime: presentationTime)
                    } else {
                        print("Failed to allocate pixel buffer")
                        appendSucceeded = false
                    }
                }
                if !appendSucceeded {
                    break
                }
                frameCount += 1
            }
            videoWriterInput.markAsFinished()
            videoWriter.finishWritingWithCompletionHandler { () -> Void in
                print("FINISHED!!!!!")
                self.compileToMakeMovie(videoOutputURL, audioOutPutURL: audioURL, completion: { url in
                    completion(url)
                })
            }
        })
    }
}

func compileToMakeMovie(videoOutputURL: NSURL, audioOutPutURL: NSURL, completion: (NSURL) -> ()){

    let mixComposition = AVMutableComposition()
    let fileManager = NSFileManager.defaultManager()
    let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
    guard let documentDirectory: NSURL = urls.first else {
        fatalError("documentDir Error")
    }

    let actualVideoURl = documentDirectory.URLByAppendingPathComponent("OutputVideoMusic.mp4")
    print("Video Output URL \(actualVideoURl)")
    if NSFileManager.defaultManager().fileExistsAtPath(actualVideoURl.path!) {
        do {
            try NSFileManager.defaultManager().removeItemAtPath(actualVideoURl.path!)
        } catch {
            fatalError("Unable to delete file: \(error) : \(#function).")
        }
    }

    let nextClipStartTime = kCMTimeZero
    let videoAsset = AVURLAsset(URL: videoOutputURL)
    let video_timeRange = CMTimeRangeMake(kCMTimeZero,videoAsset.duration)
    let a_compositionVideoTrack = mixComposition.addMutableTrackWithMediaType(AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
    try! a_compositionVideoTrack.insertTimeRange(video_timeRange, ofTrack: videoAsset.tracksWithMediaType(AVMediaTypeVideo)[0], atTime: nextClipStartTime)

    let audioAsset = AVURLAsset(URL: audioOutPutURL)
    let audio_timeRange = CMTimeRangeMake(kCMTimeZero,audioAsset.duration)
    let b_compositionAudioTrack = mixComposition.addMutableTrackWithMediaType(AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)
    do {
        try b_compositionAudioTrack.insertTimeRange(audio_timeRange, ofTrack: audioAsset.tracksWithMediaType(AVMediaTypeAudio)[0], atTime: nextClipStartTime)
    }catch _ {}


    let assetExport = AVAssetExportSession.init(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)
    assetExport?.outputFileType = "com.apple.quicktime-movie"
    assetExport?.outputURL = actualVideoURl
    assetExport?.exportAsynchronouslyWithCompletionHandler({
        completion(actualVideoURl)
    })
}

如果您仍然遇到此问题，请告诉我。