multi-camera streaming

Hello

I am currently webcasting for a client using a Vestax PBS-4 web broadcast mixer. We have three composite video channels coming in, and one audio.

My client wants to upgrade so that we can broadcast and capture in HD via their UStream channel. The stream will be captured on a MacBook Pro.

Any suggestions as to how we can do this?

Thanks for your help,

Darren

use ATEM TVS and some HD cameras ..