AE/AF lock on iPhone - turn off display?

I'm using an iPhone as a camera source via USB to record video using Quicktime on my Macbook. I want to use AE/AF Lock, but when I do, the recorded video will show the yellow square and AE/AF lock message. The only way to disable it is to unlock AE/AF. Does anyone know of a way to keep it locked, without displaying the message and square on screen? Thanks