Getting Quicktime dimensions

I'm开发者_开发技巧 having trouble with what I thought would be a simple task.

Is there a way to find the dimensions of a Quicktime file (possibly some sort of QT Media Attribute)?

I've been looking through the documentation and have yet to find something. Thanks!

NSSize movieOriginalSize = [(NSValue*)[_movie attributeForKey:QTMovieNaturalSizeAttribute] sizeValue];