Otter Media, the online-video joint venture of AT&T and Chernin Group, is in discussions with YouTube multichannel network Fullscreen to take a majority stake in the company, a source confirmed.

Reps for Otter Media and Fullscreen declined to comment. The talks were first reported by Re/code, which cited sources that said the proposed investment would value Fullscreen at between $200 million and $300 million.

The source cautioned that the deal was not final and may still fall apart. Chernin Group is already a minority shareholder in Fullscreen, along with Comcast Ventures and global ad agency WPP. Fullscreen had been in talks about an investment or acquisition with other interested parties over the last few months, including Relativity Media and Yahoo, according to sources.

SEE ALSO: AT&T, Chernin Group Invest $500 Million in Over-the-Top Video Venture

The investment, if it transpires, would be the latest in a flurry of deal activity between traditional media companies and upstart digital-video players. The biggest so far has been Disney’s acquisition of Maker Studios, the largest YouTube MCN, for $500 million plus as much as $450 million more based on performance targets.

Fullscreen was founded in January 2011 by CEO George Strompolos, a co-creator of the YouTube Partner Program. The L.A.-based company touts 425 million subscribers who watch more than 3.5 billion videos per month.

In April, AT&T and Chernin Group announced the formation of the JV, pledging to put up to $500 million toward acquiring, investing in and launching over-the-top video services. As part of the pact, Chernin Group contributed its majority stake in Crunchyroll, an online subscription VOD service focused on anime content.

Earlier this month, Otter Media acquired how-to crafting video site Creativebug from Demand Media for $10 million in cash.