Camera VPN BW Requirment between HO and Branches

Hi
i have branches with Digital Camera Installed and i connect from HO to the DVR to see the live stream video
some branch have 5 camera, other have 2 or 3
now
how can i know what is the needed Internet/VPN BW for each branch, is there are any dvr software that can measure and recommend to me the streamed video needed BW

BR
Sawyer