Capture Session Starts Up Slow - ios

Question

I am wondering why my capture session is starting up slowly when the app starts. This doesn't happen every single time I start the app, so I am not sure if it is just other variables of the actual phone or something else. I am not a very good concurrency/parallel programmer, so it is more than likely my crappy coding :(
I would GREATLY appreciate it if someone could identify what is making it slow sometimes. I have read that all calls from a capture session can be blocking, so I have tried my best to dispatch those calls to another queue without having any race conditions. I was learning about how to go about coding this way in swift form here
Here is my code where i initialize and start everything up: My queues are serial queues
/**************************************************************************
VIEW DID LOAD
***************************************************************************/
override func viewDidLoad() {
super.viewDidLoad()
println("Initializing the cameraCaptureDevice with MediaTypeVideo")
//------INIT CAMERA CAPTURE DEVICE TO BEGIN WITH------
self.cameraCaptureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
println("Done initializing camera")
var error1: NSError? = nil
println("Getting array of available capture devices")
//------GRAB ALL OF THE DEVICES------
let devices = AVCaptureDevice.devices()
//------FIND THE CAMERA MATCHING THE POSITION------
for device in devices {
if device.position == self.cameraCapturePosition {
self.cameraCaptureDevice = device as? AVCaptureDevice
println("Back camera has been added")
self.usingBackCamera = true
}
}
//------ INIT MOVIE FILE OUTPUT ------
self.movieFileOutput = AVCaptureMovieFileOutput()
//------SET UP PREVIEW LAYER-----
self.videoPreviewLayer = AVCaptureVideoPreviewLayer(session: self.session)
if let preview = self.videoPreviewLayer {
println("Video Preview Layer set")
preview.videoGravity = AVLayerVideoGravityResizeAspectFill
}
else {
println("Video Preview Layer is nil!!! Could not set AVLayerVideoGravityResizeAspectFill")
}
println("Camera successully can display")
//------SET JPEG OUTPUT------
println("Setting JPEG Output")
self.stillImageOutput = AVCaptureStillImageOutput()
let outputSettings = [ AVVideoCodecKey : AVVideoCodecJPEG ]
if let imageOutput = self.stillImageOutput {
imageOutput.outputSettings = outputSettings
}
else {
println("still image output is nil, could notset output settings")
}
println("Successfully configured JPEG Ouput")
//------SET MOVIE FILE OUPUT MAX DURATION AND MIN FREE DISK SPACE------
println("Setting Movie File Max Duration")
let maxDuration:CMTime = CMTimeMakeWithSeconds(self.totalTime, self.preferredTimeScale)
if let movieOutput = self.movieFileOutput {
movieOutput.maxRecordedDuration = maxDuration
println("Successully set movie file max duration")
println("Setting movie file minimun byte space")
movieOutput.minFreeDiskSpaceLimit = self.minFreeSpace
println("Successfully added minium free space")
}
else {
println("Movie file output is nil, could not set maximum recording duration or minimum free space")
}
//------ GRAB THE DEVICE'S SUPPORTED FRAME RATE RANGES ------
if let device = self.cameraCaptureDevice {
println("Setting frame rates")
let supportedFrameRateRanges = device.activeFormat.videoSupportedFrameRateRanges
for range in supportedFrameRateRanges {
// Workaround until finding a better way
// frame rate should be 1 - 30
if (range.minFrameRate >= 1 || range.minFrameRate <= 30) == true && (range.maxFrameRate <= 30 || range.maxFrameRate >= 1) == true {
println("Frame rate is supported")
self.frameRateSupported = true
}
else {
println("Frame rate is not supported")
self.frameRateSupported = false
}
}
var error: NSError?
if frameRateSupported && device.lockForConfiguration(&error) {
device.activeVideoMaxFrameDuration = self.frameDuration
device.activeVideoMinFrameDuration = self.frameDuration
device.unlockForConfiguration()
println("SUCCESS")
}
else {
println("frame rate is not supported or there was an error")
if let err = error {
println("There was an error setting framerate: \(err.description)")
}
else {
println("Frame rate is not supported")
}
}
}
else {
println("camera capture device is nil, could not set frame rate")
}
//------ INIT AUDIO CAPTURE DEVICE ------
self.audioCaptureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeAudio)
var error2: NSError? = nil
let audioDeviceInput = AVCaptureDeviceInput(device: self.audioCaptureDevice, error: &error2)
//------ADD CAMERA CAPTURE DEVICE TO CAPTURE SESSION INPUT------
if let captureDevice = self.cameraCaptureDevice {
if error1 == nil {
println("Trying to add video input")
self.videoDeviceInput = AVCaptureDeviceInput(device: captureDevice, error: &error1)
}
else {
println("Could not create video input")
}
}
else {
println("Could not create camera capture device")
}
//------ ADD INPUTS AND OUTPUTS AS WELL AS OTHER SESSION CONFIGURATIONS------
dispatch_async(self.sessionQueue) {
println("Trying to add audio output")
if let input = audioDeviceInput {
self.session.addInput(audioDeviceInput)
println("Successfully added audio output")
}
else {
println("Could not create audio input")
}
if self.session.canAddInput(self.videoDeviceInput) {
self.session.addInput(self.videoDeviceInput)
println("Successfully added video input")
}
else {
println("Could not add video input")
}
println("initializing video capture session")
//----- SET THE IMAGE QUALITY / RESOLUTION -----
//Options:
// AVCaptureSessionPresetHigh - Highest recording quality (varies per device)
// AVCaptureSessionPresetMedium - Suitable for WiFi sharing (actual values may change)
// AVCaptureSessionPresetLow - Suitable for 3G sharing (actual values may change)
// AVCaptureSessionPreset640x480 - 640x480 VGA (check its supported before setting it)
// AVCaptureSessionPreset1280x720 - 1280x720 720p HD (check its supported before setting it)
// AVCaptureSessionPresetPhoto - Full photo resolution (not supported for video output)
if self.session.canSetSessionPreset(AVCaptureSessionPresetHigh) {
println("Capture Session preset is set to High Quality")
self.session.sessionPreset = AVCaptureSessionPresetHigh
}
else {
println("Capture Session preset is set to Medium Quality")
self.session.sessionPreset = AVCaptureSessionPresetMedium
}
//------ADD JPEG OUTPUT AND MOVIE FILE OUTPUT TO SESSION OUTPUT------
println("Adding still image and movie file output")
if self.session.canAddOutput(self.stillImageOutput) && self.session.canAddOutput(self.movieFileOutput) {
self.session.addOutput(self.stillImageOutput)
self.session.addOutput(self.movieFileOutput)
println("Successfully added outputs")
}
else {
//------ IF OUTPUTS COULD NOT BE ADDED, THEN APP SHOULD NOT RUN ON DEVICE!!!!! ------
println("Could Not Add still image and movie file output")
}
//------WE CALL A METHOD AS IT ALSO HAS TO BE DONE AFTER CHANGING CAMERA------
self.setCameraOutputProperties()
//------DISPLAY PREVIEW LAYER------
if let videoLayer = self.videoPreviewLayer {
self.videoPreviewView.layer.addSublayer(self.videoPreviewLayer)
println("Video Preview Layer Added as sublayer")
self.videoPreviewLayer!.frame = self.videoPreviewView.layer.frame
println("Video Preview frame set")
}
else {
println("videoPreviewLayer is nil, could not add sublayer or set frame")
}
self.view.sendSubviewToBack(self.videoPreviewView)
}
}
/**************************************************************************
VIEW DID APPEAR
***************************************************************************/
override func viewDidAppear(animated: Bool) {
println("About to start the capture session")
//------INITIALIZE THE CAMERA------
dispatch_async(self.startSessionQueue) {
if self.beenHereBefore == false {
println("Have not seen this view before.... starting the session")
//------ START THE PREVIEW SESSION ------
self.startSession()
/*
CHECK TO MAKE SURE THAT THIS CODE IS REALLY NEEDED FOR AUTHORIZATION
*/
// ----- SET MEDIA TYPE ------
var mediaTypeVideo = AVMediaTypeVideo
AVCaptureDevice.requestAccessForMediaType(mediaTypeVideo, completionHandler: { (granted) -> Void in
//------ GRANTED ACCESS TO MEDIATYPE ------
if granted {
self.deviceAuthorized = AVAuthorizationStatus.Authorized
}
//------ NOT GRANTED ACCESS TO MEDIATYPE ------
else {
dispatch_async(dispatch_get_main_queue()) {
UIAlertView(title: "CopWatch", message: "CopWatch does not have permission to use the camera, please change your privacy settings.", delegate: self, cancelButtonTitle: "OK")
self.deviceAuthorized = AVAuthorizationStatus.Denied
dispatch_resume(dispatch_get_main_queue())
}
}
})
}
else {
println("Been Here Before")
self.session.startRunning()
}
self.weAreRecording = false
}
}
and here is the method that starts the video preview
/**************************************************************************
START SESSION
**************************************************************************/
func startSession() {
println("Checking to see if the session is already running before starting the session")
//------ START SESSION IF IT IS NOT ALREADY RUNNING------
if !self.session.running {
//------START CAMERA------
println("Session is not already running, starting the session now")
self.session.startRunning()
self.isSessionRunning = true
println("Capture Session initiated")
}
else {
println("Session is already running, no need to start it again")
}
}

Answer 1

It seems that I have found the answer.
I was adding the videoPreviewLayer as a subview and sending it to the back of the view in the asynchronous dispatch call. Apparently, the application did not like this and caused things to be very, very slow to start up.
I move this code
//------DISPLAY PREVIEW LAYER------
if let videoLayer = self.videoPreviewLayer {
self.videoPreviewView.layer.addSublayer(self.videoPreviewLayer)
println("Video Preview Layer Added as sublayer")
self.videoPreviewLayer!.frame = self.videoPreviewView.layer.frame
println("Video Preview frame set")
}
else {
println("videoPreviewLayer is nil, could not add sublayer or set frame")
}
self.view.sendSubviewToBack(self.videoPreviewView)
up to here like this:
//------SET UP PREVIEW LAYER-----
self.videoPreviewLayer = AVCaptureVideoPreviewLayer(session: self.session)
if let preview = self.videoPreviewLayer {
println("Video Preview Layer set")
preview.videoGravity = AVLayerVideoGravityResizeAspectFill
}
else {
println("Video Preview Layer is nil!!! Could not set AVLayerVideoGravityResizeAspectFill")
}
println("Camera successully can display")
//------DISPLAY PREVIEW LAYER------
if let videoLayer = self.videoPreviewLayer {
self.videoPreviewView.layer.addSublayer(self.videoPreviewLayer)
println("Video Preview Layer Added as sublayer")
self.videoPreviewLayer!.frame = self.videoPreviewView.layer.frame
println("Video Preview frame set")
self.view.sendSubviewToBack(self.videoPreviewView)
}
else {
println("videoPreviewLayer is nil, could not add sublayer or set frame")
}
I should have been able to see this issue, but I guess this is what happens when you optimize at the wrong times. Now it is pretty responsive.
Moral of the story, if you are programming with AVFoundation, don't set up and add your video preview layer as a subview of your view in the current view controller in an asynchronous queue.