avfoundation - 未调用 captureOutput

Question

我已经研究这个太久了。

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)到AVCaptureSession

连接 AVCaptureVideoDataOutput (作为输出)到 AVCaptureSession

调用.setSampleBufferDelegate(AVCaptureVideoDataOutputSampleBufferDelegate, DelegateQueue)

出于某种原因，在调用 .setSampleBufferDelegate(...) 后(当然，在 .startRunning() 实例上调用 AVCaptureSession 之后)，我的 AVCaptureVideoDataOutputSampleBufferDelegate的 captureOutput没有被调用。

我发现很多人在网上遇到了这个问题，但我找不到任何解决方案。

在我看来，这似乎与 DispatchQueue 有关.
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)
        }
    }

viewDidLoad 中的所有必要变量与 AVFoundation 相关已在 Viewcontroller 中实例化的 init() .为了清楚起见，我省略了这一点。

有任何想法吗？

谢谢，所以!

科韦克

编辑:
- 修复了来自 self 的设置委托(delegate)至 MyDelegate .

这就是我初始化 videoDataOutputQueue 的方式:

    videoDataOutputQueue = DispatchQueue(
        label: "VideoDataOutputQueue"   
    );

Answer 1

您在声明所需的样本缓冲区委托(delegate)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:注意该方法的参数是如何声明的。所有参数都有'!'这意味着自动展开。