Facebook is set to unveil a new video-ad product in the first half of next year in its largest attempt to date to attract big swaths of ad dollars from TV advertisers, Ad Age reports citing several industry executives who have been briefed on the company's plans over the past few weeks.

Facebook is still debating several product features, but has decided on this much to date, these executives said: By April at the latest, it will offer video advertisers the chance to target video ads to large numbers of Facebook users in their news feeds on both the desktop version of Facebook as well as on Facebook apps on mobile phones and tablets.

Facebook is leaning toward capping the length of these video ads at 15 seconds - a move that could push ad agencies normally reluctant to cut down their 30-second commercials to do so. That decision could also mean that 15-second video ads would become more prevalent elsewhere on the web.

In what's sure to be a controversial move, the visual component of the Facebook video ads will start playing automatically -- a dynamic known as "autoplay" -- according to two of the executives. Facebook is still debating whether to have the audio component of the ads activated automatically as well, one of these people said.

On the desktop version of Facebook, the video ads are expected to grab a user's attention by expanding out of the news feed into webpage real estate in both the left and right columns - or rails - of the screen. Facebook is also working on a way to ensure that the video ads stand out on the mobile apps as well, though it is unclear how exactly the company will accomplish this. (Some details about the video-ad plans remain vague and could change as Facebook gets more feedback from clients.)

Advertisers will be able to shows their video ads to desktop users of Facebook, but Facebook has been highlighting the mobile versions of the product in meetings with ad agencies, demonstrating the product on both tablets and mobile phones. Advertisers will be able to show the same video ad to a Facebook user up to three times a day across various devices, two of the executives said, according to Ad Age.