在AVCaptureSession中切换摄像机速度很慢

Question

我已经看了很多这样的问题,并尝试了很多解决方案,但这种情况有点不同.我正在使用AVCaptureVideoDataOutputSampleBufferDelegate,以便我可以将CIFilters应用于实时视频源.我正在使用以下方法来更改相机:

func changeCameras() {
    captureSession.stopRunning()
    var desiredPosition: AVCaptureDevicePosition?
    if front {
        desiredPosition = AVCaptureDevicePosition.Back
    } else {
        desiredPosition = AVCaptureDevicePosition.Front
    }

    let devices = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo) as? [AVCaptureDevice]
    for device in devices! {
        if device.position == desiredPosition {
            self.captureSession.beginConfiguration()
                do {
                    let input = try AVCaptureDeviceInput(device: device)
                    for oldInput in self.captureSession.inputs {
                        print(oldInput)
                        self.captureSession.removeInput(oldInput as! AVCaptureInput)
                    }
                  print(input)
                    self.captureSession.addInput(input)
                    self.captureSession.commitConfiguration()
                    dispatch_async(dispatch_get_main_queue(), { () -> Void in
                        self.captureSession.startRunning()
                        })

                } catch { print("evic failed")}
        }
    }
    front = !front
}

我用来设置摄像头(在viewDidLoad中调用)并从委托接收sampleBuffer的方法在这里:https://gist.github.com/JoeyBodnar/17e22e3c04093caa54cf240ed8b1b601 .

一个问题是当按下按钮来更换相机时,在更换之前需要4-5秒的固定屏幕冻结.我已经尝试了上面的方法,以及创建一个单独的队列来运行整个函数,它仍然需要很长时间.我只是在使用常规AVVideoPreviewLayer切换相机时从未遇到过这个问题,所以我认为这可能部分是因为我使用的是样本缓冲区委托,但不能完全拼凑出如何/为什么.任何帮助表示赞赏.谢谢!

Answer 1

使用DispatchQueue.global().async以便 capturesession 设置在后台完成并且 ui 不会冻结

DispatchQueue.global().async {
    self.captureSession.beginConfiguration()
    // captureSession configurations here
    
    // end with
    self.captureSession.commitConfiguration()
    DispatchQueue.main.async {
        self.captureSession.startRunning()
    }
}

这对我有用

对于您的代码，它将像这样。

func changeCameras() {
    captureSession.stopRunning()
    var desiredPosition: AVCaptureDevicePosition?
    if front {
        desiredPosition = AVCaptureDevicePosition.Back
    } else {
        desiredPosition = AVCaptureDevicePosition.Front
    }

    let devices = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo) as? [AVCaptureDevice]
    for device in devices! {
        if device.position == desiredPosition {
DispatchQueue.global().async {
            self.captureSession.beginConfiguration()
                do {
                    let input = try AVCaptureDeviceInput(device: device)
                    for oldInput in self.captureSession.inputs {
                        print(oldInput)
                        self.captureSession.removeInput(oldInput as! AVCaptureInput)
                    }
                  print(input)
                    self.captureSession.addInput(input)
                    self.captureSession.commitConfiguration()
                    dispatch_async(dispatch_get_main_queue(), { () -> Void in
                        self.captureSession.startRunning()
                        })

                } catch { print("evic failed")}
}
        }
    }
    front = !front
}