Question

我正在尝试使用AVCaptureScreenInput在Mac上进行屏幕捕获，但AVCaptureVideoDataOutput委托captureOutput永远不会被调用，我不知道为什么。我收到通知说捕获会话已经开始。

import Cocoa
import AVFoundation

class ViewController: NSViewController, AVCaptureVideoDataOutputSampleBufferDelegate {

    var captureSession: AVCaptureSession!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }

    override func viewWillAppear() {
        super.viewWillAppear()
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(ViewController.errorNotif), name: AVCaptureSessionRuntimeErrorNotification, object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(ViewController.startedNotif), name: AVCaptureSessionDidStartRunningNotification, object: nil)
        startScreenCapture()
    }

    override func viewWillDisappear() {
        super.viewWillDisappear()
        NSNotificationCenter.defaultCenter().removeObserver(self)
    }

    func captureOutput(captureOutput: AVCaptureOutput!, didDropSampleBuffer sampleBuffer: CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {
        print("ignore frame, add code to handle later")
    }

    func startScreenCapture() {

        let displayId = CGMainDisplayID()
        captureSession = AVCaptureSession()
        if captureSession.canSetSessionPreset(AVCaptureSessionPresetHigh) {
            captureSession.sessionPreset = AVCaptureSessionPresetHigh
        }
        let captureScreenInput = AVCaptureScreenInput(displayID: displayId)
        if captureSession.canAddInput(captureScreenInput) {
            captureSession.addInput(captureScreenInput)
        } else {
            print("Could not add main display to capture input")
        }

        let output = AVCaptureVideoDataOutput()

        let queue = dispatch_queue_create("myQueue", DISPATCH_QUEUE_SERIAL)
        output.setSampleBufferDelegate(self, queue: queue)
        output.alwaysDiscardsLateVideoFrames = true

        output.videoSettings = [kCVPixelBufferPixelFormatTypeKey as NSString: NSNumber(unsignedInt: kCVPixelFormatType_32BGRA)]
        captureSession.addOutput(output)
        captureSession.startRunning()
    }

    func errorNotif() {
        print("error starting capture")
    }
    func startedNotif() {
        print("started screen capture")
    }
}

Answer 1

您需要定义didOutputSampleBuffer委托回调以实际接收捕获的帧：

func captureOutput(captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {
    print("captured \(sampleBuffer)")
}

P.S。我不确定macOS，但viewWillAppear可能不适合进行初始化，因为在iOS上至少可以多次调用它。

Answer 2

我为基本示例private struct resetButton: View { @Binding var isResetting: Bool var body: some View { Button("Reset"){ self.isResetting = true } } }

添加了

resetButton()

AVCaptureVideoDataOutput captureOutput未被调用

2 个答案: