ofxQTKitVideoGrabber only audio

hi

i was wondering if it is possible to use the ofxQTKitVideoGrabber to only record audio.

i read something here about disabling the audio. which makes me think maybe there is a way to disable the video and only get the audio.

https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/QTKitApplicationProgrammingGuide/UsingQTKit/UsingQTKit.html

any ideas?
thx. s.