addInput method of QTCaptureSession not returning - objective-c

Question

I have the following code:
BOOL success;
QTCaptureSession *session = [[QTCaptureSession alloc] init];
QTCaptureDevice *device = [QTCaptureDevice defaultInputDeviceWithMediaType: QTMediaTypeVideo];
success = [device open: &e];
if ( !success )
{
NSLog(#"error opening input device: %#", e);
return;
}
QTCaptureDeviceInput *input = [QTCaptureDeviceInput deviceInputWithDevice: device];
success = [session addInput: input error: &e];
if ( !success )
{
NSLog(#"error adding input device to session: %#", e);
return;
}
QTCaptureDecompressedVideoOutput *output = [[QTCaptureDecompressedVideoOutput alloc] init];
[output setDelegate: self];
success = [session addOutput: output error: &e];
if ( !success )
{
NSLog(#"error adding output device to session: %#", e);
return;
}
[session startRunning];
this is located in a bundle loaded during runtime and is part of a method that is the selector of a NSThread (aka. it runs in in a background thread and not the main thread).
My problem is, that the call to #addInput:error: never returns. What am I missing here?

Answer 1

The problem was, that the main thread of the application was not using the Run Loop normally provided by NSApplicationMain() in Cocoa applications. Instead I was handling events within my own while loop.
The solution was calling:
CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, YES);
This thread on Apple's QuickTime mailing list for a more detailed explanation of the problem.