AVCaptureOutput captureStillImageAsynchronouslyFromConnection never completes on iPhone5 - ios

Question

In my application I am displaying a AVCaptureVideoPreviewLayer and then capturing a still image when the user clicks a button using the captureStillImageAsynchronouslyFromConnection function in AVCaptureOutput. This has worked well for me up until the iPhone 5, on which it never completes.
My setup code is:
...
self.imageOutput = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
[self.imageOutput setOutputSettings:outputSettings];
self.captureSession = [[[AVCaptureSession alloc] init] autorelease];
[self.captureSession addInput:self.rearFacingDeviceInput];
[self.captureSession addOutput:self.imageOutput];
[self.captureSession setSessionPreset:AVCaptureSessionPresetPhoto];
self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.captureSession];
self.previewLayer.frame = CGRectMake(0, 0, 320, 427);
self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspect;
[self.captureSession startRunning];
[outputSettings release];
My capture method is:
AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in self.imageOutput.connections){
for (AVCaptureInputPort *port in [connection inputPorts]){
if ([[port mediaType] isEqual:AVMediaTypeVideo] ){
videoConnection = connection;
break;
}
}
if (videoConnection) { break; }
}
//code to abort if not return 'soon'
...
[self.imageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error){
//use image here
}];
captureStillImageAsynchronouslyFromConnection never completes for me using an iPhone5
I have tested:
It isn't OS 6 as this code works on both an iPhone 4s and an iPod (iPod touch (4th generation) that have been updated
The captureSession is running
videoConnection is not nil
imageOutput is not nil
Also:
I'm using this method and not UIImagePickerController because I need to put the preview as a subview.
calling stopRunning on the capture Session takes several seconds on the iPhone 5 as well

Answer 1

Well, this code works fine. Tested for both iPhone 4 and 5, (baseSDK 7.1, under ARC).
Few things you have to consider.
1) be sure you set rearFacingDeviceInput properly,
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
[self setRearFacingDeviceInput:[AVCaptureDeviceInput deviceInputWithDevice:device error:nil]];
2) as Vincent mentioned, there will be an error, try to log both an error and imageSampleBuffer
3) session's -startRunning and -stopRunning operations takes long time to complete (seconds, even 5-6s), those methods doesn't return until they are done all the work, to avoid blocked UI you shouldn't call these methods on main thread, one way is using GCD
dispatch_queue_t serialQueue = dispatch_queue_create("queue", NULL);
dispatch_async(serialQueue, ^{
[self.captureSession startRunning];
});
If still captureStillImageAsynchronously doesn't complete (to ensure that, add breakpoint in block, and log everything) you should check your device's camera. I believe your code works on all iPhone 5 devices. Hope this helps, good luck.