AVCaptureStillImageOutput never calls completition handler - ios

Question

Following code doesn't work. Whats wrong?
AVCaptureDevice * videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput * videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:nil];
AVCaptureSession * captureSession = [[AVCaptureSession alloc] init];
captureSession.sessionPreset = AVCaptureSessionPresetMedium;
if (![captureSession canAddInput:videoInput])
NSLog(#"Can't add input");
[captureSession addInput:videoInput];
self.stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
[self.stillImageOutput setOutputSettings:#{AVVideoCodecKey:AVVideoCodecJPEG}];
if (![captureSession canAddOutput:videoInput])
NSLog(#"Can't add output");
[captureSession addOutput:self.stillImageOutput];
[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:[self.stillImageOutput.connections lastObject]
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error)
{
NSLog(#"!!!");
if (imageDataSampleBuffer == NULL)
{
NSLog(#"%#", error);
return;
}
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];
self.imageView.image = image;
}];
// Creating preview layer
self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:captureSession];
self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
self.previewLayer.frame = self.view.layer.bounds;
[self.view.layer addSublayer:self.previewLayer];
[captureSession startRunning];
AVCaptureVideoPreviewLayer works nice, but AVCaptureStillImageOutput does not call completion handler at all...

Answer 1

You need to set up & start your session in one method,
then have a separate capture method :
/////////////////////////////////////////////////
////
//// Utility to find front camera
////
/////////////////////////////////////////////////
-(AVCaptureDevice *) frontFacingCameraIfAvailable{
NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
AVCaptureDevice *captureDevice = nil;
for (AVCaptureDevice *device in videoDevices){
if (device.position == AVCaptureDevicePositionFront){
captureDevice = device;
break;
}
}
// couldn't find one on the front, so just get the default video device.
if (!captureDevice){
captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}
return captureDevice;
}
/////////////////////////////////////////////////
////
//// Setup Session, attach Video Preview Layer
//// and Capture Device, start running session
////
/////////////////////////////////////////////////
-(void) setupCaptureSession {
AVCaptureSession *session = [[AVCaptureSession alloc] init];
session.sessionPreset = AVCaptureSessionPresetMedium;
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
[self.view.layer addSublayer:captureVideoPreviewLayer];
NSError *error = nil;
AVCaptureDevice *device = [self frontFacingCameraIfAvailable];
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if (!input) {
// Handle the error appropriately.
NSLog(#"ERROR: trying to open camera: %#", error);
}
[session addInput:input];
self.stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
[self.stillImageOutput setOutputSettings:outputSettings];
[session addOutput:self.stillImageOutput];
[session startRunning];
}
/////////////////////////////////////////////////
////
//// Method to capture Still Image from
//// Video Preview Layer
////
/////////////////////////////////////////////////
-(void) captureNow {
AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in self.stillImageOutput.connections) {
for (AVCaptureInputPort *port in [connection inputPorts]) {
if ([[port mediaType] isEqual:AVMediaTypeVideo] ) {
videoConnection = connection;
break;
}
}
if (videoConnection) { break; }
}
NSLog(#"about to request a capture from: %#", self.stillImageOutput);
__weak typeof(self) weakSelf = self;
[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) {
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];
[weakSelf displayImage:image];
}];
}

Answer 2

This works well:
- (void)viewDidLoad
{
[super viewDidLoad];
AVCaptureDevice * videoDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput * videoInput = [AVCaptureDeviceInput deviceInputWithDevice:videoDevice error:nil];
AVCaptureSession * captureSession = [[AVCaptureSession alloc] init];
captureSession.sessionPreset = AVCaptureSessionPresetMedium;
[captureSession addInput:videoInput];
[captureSession addOutput:self.stillImageOutput];
[captureSession startRunning];
// Creating preview layer
self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:captureSession];
self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
self.previewLayer.frame = self.view.layer.bounds;
[self.view.layer insertSublayer:self.previewLayer atIndex:0];
}
- (void)timerFired:(NSTimer *)timer
{
[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:[self.stillImageOutput.connections lastObject]
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error)
{
NSLog(#"!!!");
if (imageDataSampleBuffer == NULL)
NSLog(#"%#", error);
NSData * imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage * image = [[UIImage alloc] initWithData:imageData];
self.imageView.image = image;
}];
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:#selector(timerFired:) userInfo:nil repeats:YES];
}