QTCaptureOutput.delegate captureOutput:didOutputVideoFrame:... never called - objective-c

Question

Source
So, I have a QTCaptureSession set up thusly:
//Setup Camera
cameraSession = [[QTCaptureSession alloc] init];
QTCaptureDevice *camera = [QTCaptureDevice deviceWithUniqueID: cameraID];
BOOL success = [camera open: &error];
if (!success || error)
{
NSLog(#"Could not open device %#.", cameraID);
NSLog(#"Error: %#", [error localizedDescription]);
return nil;
}
//Setup Input Session
QTCaptureDeviceInput *cameraInput = [[QTCaptureDeviceInput alloc] initWithDevice: camera];
success = [cameraSession addInput: cameraInput error: &error];
if (!success || error)
{
NSLog(#"Could not initialize input session.");
NSLog(#"Error: %#", [error localizedDescription]);
return nil;
}
//Setup Output
QTCaptureDecompressedVideoOutput *cameraOutput = [[QTCaptureDecompressedVideoOutput alloc] init];
[cameraOutput setDelegate: self];
success = [cameraSession addOutput: cameraOutput error: &error];
if (!success || error)
{
NSLog(#"Could not initialize output session.");
NSLog(#"Error: %#", [error localizedDescription]);
return nil;
}
And the QTCaptureDecompressedVideoOutput delegate's captureOutput:didOutputVideoFrame:WithSampleBuffer:fromConnection: thusly:
- (void)captureOutput:(QTCaptureOutput *)captureOutput didOutputVideoFrame:(CVImageBufferRef)videoFrame withSampleBuffer:(QTSampleBuffer *)sampleBuffer fromConnection:(QTCaptureConnection *)connection
{
NSLog(#"starting convert\n");
}
I then start the capture processing using:
[cameraSession startRunning];
All of the variables initialize fine, and the session starts fine, but captureOutput:didOutputVideoFrame:withSampleBuffer:fromConnection: never gets called.
Context
This is a command-line app, compiled with the GCC. It's linked against the following frameworks:
Foundation
Cocoa
QTKit
QuartzCore
Relevant Miscellany
The frame is not likely dropping because captureOutput:didDropVideoFrameWithSampleBuffer:fromConnection: is also not getting called.

Answer 1

So, with some help from Mike Ash, I managed to figure out that my program was terminating immediately and not waiting for the delegate callback (which, according to Apple's QTKit docs, might occur on a separate thread).
My solution was to add a BOOL properties to my object named captureIsFinished, then add this to the main() function:
//Wait Until Capture is Finished
while (![snap captureIsFinished])
{
[[NSRunLoop currentRunLoop] runUntilDate: [NSDate dateWithTimeIntervalSinceNow: 1]];
}
Which effectively perpetuates the run-loop of the app for 1 second, checks to see if the capture is finished, then runs for another second.