在Swift中使用AVAssetWriter将AVCaptureVideoDataOutput保存到电影文件 [英] Save AVCaptureVideoDataOutput to movie file using AVAssetWriter in Swift

问题描述

我一直在网上浏览所有内容，似乎找不到所需的教程或帮助.

I've been looking all over the web and can't seem to find a tutorial or help in what I need.

使用AVFoundation和Dlib库，我创建了一个应用程序，可以使用手机上的前置摄像头从实时视频中检测人脸.我正在使用Shape Predictor 68 Face Landmark s执行此操作.为此，我敢肯定我必须使用AVCaptureVideoDataOutput而不是AVMovieFileOutput，以便可以分析每个帧.

Using AVFoundation and the Dlib library I've created an app that can detect a face from real time video using the front camera on the phone. I'm doing this using Shape Predictor 68 Face Landmarks. For this to work I'm pretty sure I have to use AVCaptureVideoDataOutput as opposed to AVMovieFileOutput so that each frame can be analysed.

我现在希望能够将视频保存到文件中，根据我收集的信息，我需要使用AVAssetWriter来执行此操作.我只是在任何地方都找不到太多有关如何开始使用此方法的信息.我对Swift和iOS编程是完全陌生的，对Apple文档的了解并不多.

I now want to be able to save the video to file and from what I gather I need to use AVAssetWriter to do this. I just can't find much information anywhere about how to get started with this. I'm completely new to Swift and iOS programming and can't really understand much from looking at Apple's documentation.

如果有人可以帮助我，将不胜感激！

If anyone could help me would be greatly appreciated!

推荐答案

我能够找到如何使用AVAssetWriter的方法.万一其他人需要帮助，我使用的代码如下:

I was able to find out how to use AVAssetWriter. In case anyone else needs help the code I used is as follows:

func setUpWriter() {

    do {
        outputFileLocation = videoFileLocation()
        videoWriter = try AVAssetWriter(outputURL: outputFileLocation!, fileType: AVFileType.mov)

        // add video input
        videoWriterInput = AVAssetWriterInput(mediaType: AVMediaType.video, outputSettings: [
            AVVideoCodecKey : AVVideoCodecType.h264,
            AVVideoWidthKey : 720,
            AVVideoHeightKey : 1280,
            AVVideoCompressionPropertiesKey : [
                AVVideoAverageBitRateKey : 2300000,
                ],
            ])

        videoWriterInput.expectsMediaDataInRealTime = true

        if videoWriter.canAdd(videoWriterInput) {
            videoWriter.add(videoWriterInput)
            print("video input added")
        } else {
            print("no input added")
        }

        // add audio input
        audioWriterInput = AVAssetWriterInput(mediaType: AVMediaType.audio, outputSettings: nil)

        audioWriterInput.expectsMediaDataInRealTime = true

        if videoWriter.canAdd(audioWriterInput!) {
            videoWriter.add(audioWriterInput!)
            print("audio input added")
        }


        videoWriter.startWriting()
    } catch let error {
        debugPrint(error.localizedDescription)
    }


}

func canWrite() -> Bool {
    return isRecording && videoWriter != nil && videoWriter?.status == .writing
}


 //video file location method
func videoFileLocation() -> URL {
    let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString
    let videoOutputUrl = URL(fileURLWithPath: documentsPath.appendingPathComponent("videoFile")).appendingPathExtension("mov")
    do {
    if FileManager.default.fileExists(atPath: videoOutputUrl.path) {
        try FileManager.default.removeItem(at: videoOutputUrl)
        print("file removed")
    }
    } catch {
        print(error)
    }

    return videoOutputUrl
}

// MARK: AVCaptureVideoDataOutputSampleBufferDelegate
func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {

    let writable = canWrite()

    if writable,
        sessionAtSourceTime == nil {
        // start writing
        sessionAtSourceTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
        videoWriter.startSession(atSourceTime: sessionAtSourceTime!)
        //print("Writing")
    }

    if output == videoDataOutput {
        connection.videoOrientation = .portrait

        if connection.isVideoMirroringSupported {
            connection.isVideoMirrored = true
        }
    }

    if writable,
        output == videoDataOutput,
        (videoWriterInput.isReadyForMoreMediaData) {
        // write video buffer
        videoWriterInput.append(sampleBuffer)
        //print("video buffering")
    } else if writable,
        output == audioDataOutput,
        (audioWriterInput.isReadyForMoreMediaData) {
        // write audio buffer
        audioWriterInput?.append(sampleBuffer)
        //print("audio buffering")
    }

}

// MARK: Start recording
func start() {
    guard !isRecording else { return }
    isRecording = true
    sessionAtSourceTime = nil
    setUpWriter()
    print(isRecording)
    print(videoWriter)
    if videoWriter.status == .writing {
        print("status writing")
    } else if videoWriter.status == .failed {
        print("status failed")
    } else if videoWriter.status == .cancelled {
        print("status cancelled")
    } else if videoWriter.status == .unknown {
        print("status unknown")
    } else {
        print("status completed")
    }

}

// MARK: Stop recording
func stop() {
    guard isRecording else { return }
    isRecording = false
    videoWriterInput.markAsFinished()
    print("marked as finished")
    videoWriter.finishWriting { [weak self] in
        self?.sessionAtSourceTime = nil
    }
    //print("finished writing \(self.outputFileLocation)")
    captureSession.stopRunning()
    performSegue(withIdentifier: "videoPreview", sender: nil)
}

我现在有另一个问题，当我同时使用AVCaptureMetadataOutput，AVCaptureVideoDataOutput和AVCaptureAudioDataOutput时，此解决方案不起作用.当我添加AVCaptureAudioDataOutput时，应用程序崩溃.

I now have another problem where this solution doesn't work when I'm using AVCaptureMetadataOutput, AVCaptureVideoDataOutput and AVCaptureAudioDataOutput together. The app crashes when I add AVCaptureAudioDataOutput.

这篇关于在Swift中使用AVAssetWriter将AVCaptureVideoDataOutput保存到电影文件的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！