Ok. Curiosity did hit me again. That evil thing... :evil: :evil:

:-D
(I like technology stuff, too...)
I have gone as far as digging now a bit about it (some minutes. Probably there's a lot more out there)
This below may not help at all. Or all the opposite. These are my fast findings :
- CPU, video card, etc. I am not asking what computer you have. But pointing out that it can happen with underpowered computers, or if you are multitasking heavily at the moment, etc.
- Logitech support FAQ for your cam model.
http://www.logitech.com/en-us/support/h ... =14&bit=64
- Some more help with tips in the Logitech site:
http://logitech-en-amr.custhelp.com/app ... 5/cl/us,en
- Finally, but maybe, the most important point (if it can help to MFC broadcasting somehow, I don't have a clue, as I just digged about this extremely fast) is a video where a guy tells you about a really cheap itunes app (I think 8$) that is called "Webcam Settings", that in different sources I am finding that helps with your exact model. It might help a real lot, go check it.
http://youtu.be/6W1ct0yOpwU
The app itself, it seems is here (but double check your self if is the one the guy says)
https://itunes.apple.com/us/app/webcam- ... 6630?mt=12
A version of it, free. (but unless you are literally in extreme poverty, go all the way and purchase it, as I have read that is more powerful the commercial one. Anyway, you might want to try it too, in case the other one fails. The free one seems to be offered by Logitech)
https://itunes.apple.com/us/app/logitec ... mpt=uo%3D4
Final note: This are all facts I have not checked myself. But that seem to lead to a good solution. Also, it seems the problem is that this exact model is not well supported in the Mac, and that is probably what happens.
Note: One thing I have read in several places is, check that you count on USB 2.0 ports in your computer. I'm a Windows user, so a bit lost in all what is Mac related.
Very last note: I would need to test the app to know if helps some how with the pixelation problems. It sure helps with the camera controls. If it doesn't, checking fully the Logitech c920 FAQs linked above would totally help.
Cheers !