Saving CMSampleBufferRef for later processing

I am trying to use AVFoundation framework to capture a 'series' of still images from AVCaptureStillImageOutput QUICKLY, like the burst mode in some cameras. I want to use the completion handler,

    [stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection 
                                              completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) { 

and pass the imageSampleBuffer to an NSOperation object for later processing. However i cant find a way to retain the buffer in the NSOperation class.

    [stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection 
                                              completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) { 

    //Add to queue
    SaveImageDataOperation *saveOperation = [[SaveImageDataOperation alloc] initWithImageBuffer:imageSampleBuffer];
    [_saveDataQueue addOperation:saveOperation];
    [saveOperation release];

    //Continue
    [self captureCompleted];
}];

Does any one know what I maybe doing wrong here? Is there a better approach to do this?

IMPORTANT: Clients of CMSampleBuffer must explicitly manage the retain count by calling CFRetain and CFRelease, even in processes using garbage collection.

SOURCE: CoreMedia.Framework CMSampleBuffer.h