Yes
do not setup a
subdomain. You must contact your hosting company, and have them setup the CNAME record for you. Unless you have access to it yourself. Tell them you need a CNAME record to point from videos.yourdomain.com to vidiac.com (not
www.vidiac.com, nor the ip address to their site) They should be able to help you.
More information about CNAME records can be found on the Vidiac website. I will not support Vidiac, they have thier own site, and forums to help you setup the Vidiac Video Portal.
http://www.vidiac.com/Installationfaq.aspx#cname