avfoundation - Camera frames dropped after changing camera iOS -

my method didoutputsamplebuffer called until switch cameras using function:

func switchcameras() {      capturesession.beginconfiguration()     capturesession.sessionpreset = avcapturesessionpresetmedium     var error : nserror? = nil     input in capturesession.inputs {         capturesession.removeinput(input as! avcaptureinput)     }     if currentcamera == "back" {         currentcamera = "front"          if capturesession.canaddinput(avcapturedeviceinput(device: frontcamera, error: &error)) {             capturesession.addinput(avcapturedeviceinput(device: frontcamera, error: &error))         } else {             print(error)         }     } else {         currentcamera = "back"         if capturesession.canaddinput(avcapturedeviceinput(device: backcamera, error: &error)) {             capturesession.addinput(avcapturedeviceinput(device: backcamera, error: &error))         } else {         }     }     print("chagned")     capturesession.commitconfiguration() } 

after switching, frames dropped in method, can't take picture. after 5 seconds, frames come back.

func captureoutput(captureoutput: avcaptureoutput!, didoutputsamplebuffer samplebuffer: cmsamplebuffer!, fromconnection connection: avcaptureconnection!) {     connection.videoorientation = avcapturevideoorientation.portrait      if capture == true {         self.capture = false         var newbuffer = samplebuffer             self.capturepicture(newbuffer)       } } 

if need more code let me know.

i solved changing output queue dispatch_queue_serial.

let output = avcapturevideodataoutput() output.videosettings = [kcvpixelbufferpixelformattypekey nsstring:kcvpixelformattype_32bgra] let queue = dispatch_queue_create("cameraqueue", dispatch_queue_serial) output.setsamplebufferdelegate(self, queue: dispatch_get_main_queue())