LAS VEGAS — The way TV ads are bought and sold is about to look a lot more like the web – but the web will have to look like TV first, says the chairman of the world’s largest media investment agency.

“Television is sold on a 30-second spot basis, while digital is sold on an impression basis,” Group M’s Irwin Gotlieb tells Beet.TV in this video interview. “Over time, television will begin go evolve in to the sale of impressions – that will gradually become the unit of sale.”

But, today, there are some sticking points, Gotlieb says: “On the television side, we know what content parameters are – we know what kind of content we’re buying (for advertisers)…  on the web side, not so much.

“There’s a lot of work that needs to be done to determine how best to filter the content on the web, to decide what’s appropriate for clients and isn’t.”

He was interviewed for Beet.TV at the Consumer Electronics Show in Las Vegas.

Beet.TV coverage of CES 2015 is sponsored by Adobe Primetime. Find all the coverage here.