Begin new captureSession without removing previewLayer - ios

Question

I'm creating a customView for the CameraView, which works fine however i'm now working on changing from the back camera to the front camera. i've at the moment done it by doing below. However this seem to create a bad user experience where it removes the previewLayer (the screen becomes white) and then show the front camera correctly. is there a way to create a better user experience by not making everything white in 1 sec before showing the new session?
switchCamera
func switchCamera() {
if usingbackCamera == true {
endSession()
beginSession(frontCamera!)
usingbackCamera = false
self.cameraView.bringSubviewToFront(actionView)
} else {
endSession()
beginSession(backCamera!)
usingbackCamera = true
self.cameraView.bringSubviewToFront(actionView)
}
}
beginSession
func beginSession(device: AVCaptureDevice) {
do {
captureSession.addInput(try AVCaptureDeviceInput(device: device))
self.previewLayer?.removeFromSuperlayer()
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
self.cameraView.layer.addSublayer(previewLayer!)
previewLayer?.frame = self.cameraView.bounds
captureSession.startRunning()
stillImageOutput.outputSettings = [AVVideoCodecKey:AVVideoCodecJPEG]
if captureSession.canAddOutput(stillImageOutput) {
captureSession.addOutput(stillImageOutput)
}
if captureSession.canAddOutput(videoOutput) {
captureSession.addOutput(videoOutput)
}
} catch let err as NSError {
print(err)
}
}
endSession
func endSession() {
self.previewLayer?.removeFromSuperlayer()
captureSession.stopRunning()
captureSession = AVCaptureSession()
}
Take Picture
func takePicture() {
if let videoConnection = stillImageOutput.connectionWithMediaType(AVMediaTypeVideo){
videoConnection.videoOrientation = AVCaptureVideoOrientation.Portrait
stillImageOutput.captureStillImageAsynchronouslyFromConnection(videoConnection, completionHandler: {
(sampleBuffer, error) in
let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(sampleBuffer)
let dataProvider = CGDataProviderCreateWithCFData(imageData)
let cgImageRef = CGImageCreateWithJPEGDataProvider(dataProvider, nil, true, CGColorRenderingIntent.RenderingIntentDefault)
let image = UIImage(CGImage: cgImageRef!, scale: 1.0, orientation: UIImageOrientation.Right)
self.previewImageView.image = image
self.previewImageView.hidden = false
self.cameraView.bringSubviewToFront(self.previewImageView)
})
}
}

Answer 1

You don't need to stop the captureSession and start it again when switching from back to front camera and vice versa.
All you need to do is remove the old capture session inputs, add the new one and all that in between a begin/commit session configuration block.
Here is a rough example:
func switchCamera() {
//begin configuration changes
captureSession.beginConfiguration()
//remove the previous inputs
let inputs = captureSession.inputs as! [AVCaptureInput]
for oldInput:AVCaptureInput in inputs {
captureSession.removeInput(oldInput)
}
//add the new input
if usingbackCamera == true {
addInput(frontCamera!)
usingbackCamera = false
self.cameraView.bringSubviewToFront(actionView)
}
else {
addInput(backCamera!)
usingbackCamera = true
self.cameraView.bringSubviewToFront(actionView)
}
//end the configuration
captureSession.commitConfiguration()
}
func addInput(device: AVCaptureDevice) {
do {
captureSession.addInput(try AVCaptureDeviceInput(device: device))
} catch let err as NSError {
print(err)
}
}

Answer 2

I think you don't have to remove the preview layer when changing the input device.
The layer is bond to the session, all you have to do is stop the session, remove the original input and add the new input then start the session again.
I make my capture view by custom rendering, but I thought the process will be the same.
The capture snippet:
for output in session.outputs {
if let capture = output as? AVCaptureStillImageOutput{
for connection in (capture.connections as! [AVCaptureConnection]){
for port in (connection.inputPorts as! [AVCaptureInputPort]){
if port.mediaType == AVMediaTypeVideo{
capture.captureStillImageAsynchronouslyFromConnection(connection, completionHandler: {(buffer, err) -> Void in
if err != nil{
print(err)
}
let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer)
guard let image = CIImage(data: imageData) else{
completion(nil)
return
}
let rotatedImage = image.imageByApplyingTransform(CGAffineTransformMakeRotation(-CGFloat(M_PI_2)))
})
}
}
}
}
}