如何使用AVCaptureSession流式传输实时预览视频,然后拍照,然后返回流式传输

let captureSession = AVCaptureSession()
let videoDevice = AVCaptureDevice.default(for: .video)
let videoInput = try AVCaptureDeviceInput(device: videoDevice!)
let videoOutput = AVCaptureVideoDataOutput()
videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue(label: "sample buffer delegate"))
captureSession.addInput(videoInput)
captureSession.addOutput(videoOutput)

let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.bounds
view.layer.addSublayer(previewLayer)
captureSession.startRunning()

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
    // 获取帧数据
    let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
    // 将帧数据转换为图片
    let ciImage = CIImage(cvImageBuffer: imageBuffer!)
    let image = UIImage(ciImage: ciImage)
    // 将图片显示在预览视图上
    previewLayer.contents = image?.cgImage
}

func takePhoto() {
    let videoConnection = videoOutput.connection(with: .video)
    videoOutput.captureStillImageAsynchronously(from: videoConnection!) { (buffer, error) in
        let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer!)
        let image = UIImage(data: imageData!)
        UIImageWriteToSavedPhotosAlbum(image!, nil, nil, nil)
    }
}

captureSession.stopRunning()
previewLayer.removeFromSuperlayer()
captureSession.removeInput(videoInput)
captureSession.removeOutput(videoOutput)