The UltraViolet platform has attracted 750,000 households to create accounts since the digital rights locker opened its doors in October.

That’s far from the tens of millions Hollywood is waiting for to call UltraViolet a mass-market product — and add more movies than the initial 19 titles currently available.

But the Digital Entertainment Content Ecosystem (DECE), the large consortium of more than 75 content owners, retailers and tech firms, will launch a major multimillion dollar marketing campaign to lure more users this year, with the ad effort set to bow in the fourth quarter.

Mark Teitell, the DECE’s general manager and executive director, said from a Tuesday press event at CES, that new marketing materials would look to create a consistent message to drive mass adoption among consumers under the slogan, “Your movies in the cloud.”

Key to growing UltraViolet is getting more consumers used to what UltraViolet does, studio chiefs said. And adding more content, of course.

This year, Sony Pictures, Universal and Warner Bros. will make most of their theatrical releases, as well as studio catalogs and TV titles available with UltraViolet rights, with hundreds of millions of UltraViolet-enabled DVD’s and Blu-rays to hit U.S. shelves in 2012. Paramount also recently announced that the Jan. 24 release of “Paranormal Activity 3” will be UltraViolet-enabled, its first such title.

Fox views UltraViolet as “a component to the digital ecosystem we’re trying to construct and not the digital ecosystem, itself,” according to Mike Dunn, president of Fox Home Entertainment. “Our job is to build this digital ecosystem to deliver an exciting and simple customer experience that we hope will lead to mass consumer adoption. It’s not going to lead to mass consumer adoption if our infrastructure is not successful.”

Dunn added that the purpose of UV is to restore the consumer purchase model to the level at the height of DVDs’ popularity.

But studios say that will take some time, with UV not expected to come out of its current beta mode until the fourth quarter. Many of DECE’s members have stressed that they didn’t want to wait to launch UV until it was completely perfect; they wanted to fix the system’s bugs as consumers learn how UV will benefit them and enable them to seamlessly transfer their films to 12 different devices, similar to how they can currently move songs or e-books around.

The magic number to reach that mass market is 25 million, many say.

“When you’re talking 25 million members or people involved with UV, that starts to become mainstream,” Dunn said. “Blu-ray has tipped into the mass market now and it did that when it crossed the 25 million household mark,” especially with more people buying older catalog titles and family films.

“I think we’re on the verge of another monumental event, because very rarely do you have the living room escalating into high-def TVs, thin TVs, and portable devices proliferating at a rate that’s never been seen before,” Dunn added. “It really allows the consumer very simple operation to move rights around. Rights extension is what made DVD what it was, and this is rights extension on steroids.”

Also expected to help grow UltraViolet’s usage is a new deal between Amazon and a major studio to support UltraViolet rights.

The e-tailing giant, however, is keeping quiet on just which studio that is.

“We have to keep that a secret,” said Bill Carr, executive VP, digital media for Amazon.

Samsung also unveiled a new smart Blu-ray player with a “disc-to-digital” feature that adds titles from consumers’ existing DVD and Blu-ray collections to their UltraViolet locker. When a disk is inserted in the player, the consumer gets the option to add it to UltraViolet, and if it’s a DVD, they can upgrade to HD for “a nominal fee.” The app was developed by Flixster and Rovi.

Netflix won’t be part of UltraViolet’s growth, however.

The company was not on stage during the DECE’s press conference — mainly because it’s no longer a DECE member.

UltraViolet is aimed at ownership, not rental, DECE members said, and Netflix is not interested in getting into sell-through to buyers anytime soon.

Only a few minutes was spent on Disney’s decision to hold out from being an official DECE member.

“I don’t think there’s any company we haven’t talked to about UltraViolet,” said Mitch Singer, chief technology officer for Sony Pictures Entertainment. “It would be terrific to have them join. I’m not holding my breath but we’re certainly talking.”