iOS7 AVCapture captureOutput never gets called - ios

Question

Please understand that I cannot upload the whole code here.
I have
#interface BcsProcessor : NSObject <AVCaptureMetadataOutputObjectsDelegate> {}
and BcsProcessor has setupCaptureSession and captureOutput method.
- (void)captureOutput:(AVCaptureOutput*)captureOutput didOutputMetadataObjects:(NSArray*)metadataObjects fromConnection:(AVCaptureConnection*)connection
- (NSString*)setUpCaptureSession {
NSError* error = nil;
AVCaptureSession* captureSession = [[[AVCaptureSession alloc] init] autorelease];
self.captureSession = captureSession;
AVCaptureDevice* __block device = nil;
if (self.isFrontCamera) {
NSArray* devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
[devices enumerateObjectsUsingBlock:^(AVCaptureDevice *obj, NSUInteger idx, BOOL *stop) {
if (obj.position == AVCaptureDevicePositionFront) {
device = obj;
}
}];
} else {
device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}
AVCaptureDeviceInput* input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
AVCaptureMetadataOutput* output = [[[AVCaptureMetadataOutput alloc] init] autorelease];
output.metadataObjectTypes = output.availableMetadataObjectTypes
dispatch_queue_t outputQueue = dispatch_queue_create("com.1337labz.featurebuild.metadata", 0);
[output setMetadataObjectsDelegate:self queue:outputQueue];
captureSession.sessionPreset = AVCaptureSessionPresetPhoto;
if ([captureSession canAddInput:input]) {
[captureSession addInput:input];
}
if ([captureSession canAddOutput:output]) {
[captureSession addOutput:output];
}
// setup capture preview layer
self.previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:captureSession];
// run on next event loop pass [captureSession startRunning]
[captureSession performSelector:#selector(startRunning) withObject:nil afterDelay:0];
return nil;
}
So the code above sets up the session and add AVCaptureMetadataOutput. and BcsProcessor is supposed to receive the captured metadata. but my captureOutput method does not receive any data, or gets called.
I'll appreciate any help or comments.

Answer 1

First make sure your input and output are correctly added to the session. You can check by logging captureSession.inputs and captureSession.outputs.
Second make sure output.metadataObjectTypes is correctly setup meaning output of availableMetadataObjectTypes is not empty. I believe this will be empty if you call it before adding the output.
and finally i don't see you adding the preview layer to the views layer
try after you init your layer with session...
self.previewLayer.frame = self.view.layer.bounds;
[self.view.layer addSublayer:previewLayer];