My photo booth keeps freezing up whenever I'm filming / recording vocals. It just stops and starts. Is there an upgrade or a way to fix this annoying prob?

I just upgraded my iMac desktop to El Captian and all is working fine, but the photo booth. Whenever I try to film myself singing or talking about whatever, it'll freeze up mid way through. The recording still picks up the vocals. The footage goes in and out / stop and starts. Is there an upgrade or a way to fix this annoying problem?

Thank you in advance!

James

OS X El Capitan

v 10.11.6

iMac 21.5-inch Mid 2011

Processor 2.5 GHz Intel Core 15

Memory 4GB 1333 MHz DDR3