captureOutput未被调用

Question

我一直在研究这个问题太久了.

我正在尝试获取MacOS网络摄像头数据并在网络摄像头输出的帧上运行CIDetect.

我知道我需要:

• 连接AVCaptureDevice(如输入中)到AVCaptureSession

• 连接AVCaptureVideoDataOutput(作为输出)到AVCaptureSession

• 呼叫 .setSampleBufferDelegate(AVCaptureVideoDataOutputSampleBufferDelegate, DelegateQueue)

出于某种原因,打完电话后.setSampleBufferDelegate(...)(当然调用后.startRunning()的AVCaptureSession实例),我AVCaptureVideoDataOutputSampleBufferDelegate的captureOutput不会被调用.

我发现有这么多人在网上遇到麻烦,但我找不到任何解决方案.

在我看来,它与它有关DispatchQueue.

MyDelegate.swift:

class MyDelegate : NSObject {


    var context: CIContext?;
    var detector : CIDetector?;

    override init() {
        context = CIContext();
        detector = CIDetector(ofType: CIDetectorTypeFace, context: context);
        print("set up!");

    }

}
extension MyDelegate : AVCaptureVideoDataOutputSampleBufferDelegate {
    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection) {
        print("success?");
        var pixelBuffer : CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!;
        var image : CIImage = CIImage(cvPixelBuffer: pixelBuffer);
        var features : [CIFeature] = detector!.features(in: image);
        for feature in features {
            print(feature.type);
            print(feature.bounds);
        }
    }

    func captureOutput(_ : AVCaptureOutput, didDrop sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection) {
        print("fail?");
    }
}

ViewController.swift:

var captureSession : AVCaptureSession;
var captureDevice : AVCaptureDevice?
var previewLayer : AVCaptureVideoPreviewLayer?

var vdo : AVCaptureVideoDataOutput;

var videoDataOutputQueue : DispatchQueue;

override func viewDidLoad() {
    super.viewDidLoad()

    camera.layer = CALayer()

    // Do any additional setup after loading the view, typically from a nib.
    captureSession.sessionPreset = AVCaptureSessionPresetLow

    // Get all audio and video devices on this machine
    let devices = AVCaptureDevice.devices()

    // Find the FaceTime HD camera object
    for device in devices! {
        print(device)

        // Camera object found and assign it to captureDevice
        if ((device as AnyObject).hasMediaType(AVMediaTypeVideo)) {
            print(device)
            captureDevice = device as? AVCaptureDevice
        }
    }

    if captureDevice != nil {
        do {   
            try captureSession.addInput(AVCaptureDeviceInput(device: captureDevice))
            // vdo : AVCaptureVideoDataOutput;
            vdo.videoSettings = [kCVPixelBufferPixelFormatTypeKey as AnyHashable: NSNumber(value: kCVPixelFormatType_32BGRA)]

            try captureDevice!.lockForConfiguration()
            captureDevice!.activeVideoMinFrameDuration = CMTimeMake(1, 30)
            captureDevice!.unlockForConfiguration()

            videoDataOutputQueue.sync{
                vdo.setSampleBufferDelegate(
                    MyDelegate,
                    queue: videoDataOutputQueue
                );
                vdo.alwaysDiscardsLateVideoFrames = true
                captureSession.addOutput(vdo)   
                captureSession.startRunning();
            }
        } catch {
            print(AVCaptureSessionErrorKey.description)
        }
    }

里面所有必要的变量viewDidLoad与AVFoundation被实例里面Viewcontroller的init().为清楚起见,我省略了.

有任何想法吗？

谢谢,所以!

Kovek

编辑: -修正了设置委托self给MyDelegate.

这就是我初始化的方式videoDataOutputQueue:

    videoDataOutputQueue = DispatchQueue(
        label: "VideoDataOutputQueue"   
    );

Answer 1

我有一个类似的问题:在我的情况下问题是在Swift 4中编写你必须实现以下方法:

func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) 

代替:

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!)

希望能帮助到你.

编辑

此方法必须由AVCaptureMetadataOutputObjectsDelegate(例如,您的viewcontroller)实现.要启动QRCode捕获会话,您可以尝试这样的事情:

    captureSession = AVCaptureSession()

    let videoCaptureDevice = AVCaptureDevice.default(for: AVMediaType.video);
    var videoInput:AVCaptureDeviceInput? =  nil;

    do {
        if let v = videoCaptureDevice{
            videoInput = try AVCaptureDeviceInput(device: v)
        }
        else{
            print("Error: can't find videoCaptureDevice");
        }

    } catch {
        let ac = UIAlertController(title: "Error", message: error.localizedDescription, preferredStyle: .alert)
        ac.addAction(UIAlertAction(title: "Ok", style: .default))
        present(ac, animated: true)
        return
    }

    if let videoInput = videoInput{
        if (captureSession.canAddInput(videoInput)) {
            captureSession.addInput(videoInput)
        } else {
            //Show error
            return;
        }
    }
    else{
        //Show error
        return;
    }

    let metadataOutput = AVCaptureMetadataOutput()

    if (captureSession.canAddOutput(metadataOutput)) {
        captureSession.addOutput(metadataOutput);

        metadataOutput.setMetadataObjectsDelegate(/*YOUR DELEGATE*/, queue: DispatchQueue.main);
        metadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.qr, AVMetadataObject.ObjectType.code128];
    } else {
        //Show error
        return;
    }

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession);
    previewLayer.frame = view.layer.bounds;

    previewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill;
    view.layer.addSublayer(previewLayer);

    captureSession.startRunning();

Answer 2

您在声明所需的样本缓冲区委托方法时犯了一个错误:

captureOutput(_:didOutputSampleBuffer:from:).

请检查并确保它是:

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!)

PS:注意如何声明该方法的参数.所有参数都有'!' 这意味着自动展开.