How fast can you scroll? Facebook's 15-second video ads hitting your News Feed soon

Facebook Inc will allow more marketers to run video advertisements on its website, provided the world’s No 1 social network deem them to be of high-enough quality.   Facebook and social media rivals like Twitter are increasingly trying to grab a slice of lucrative TV-marketing budgets as they try to sustain rapid growth. That market is considered crucial to supporting Facebook’s growing market valuation and poses a potential long-term threat to traditional TV networks.   Facebook has moved cautiously to avoid annoying users. Social media players like Twitter are typically careful not to clutter up their users’ pages with unwanted material.   The 15-second video ads, which appear in newsfeeds and will play automatically with sound muted, will become available to a limited number of marketers over the next few months, Facebook said on its official blog on Thursday. It first tested video ads with a single advertiser in December. Facebook said that video ads will be available to a “a select group of advertisers,” without details.   The price that marketers pay to run a video ad on Facebook will be determined by the size of the audience as measured by measurement firm Nielsen, Facebook added. Marketers will be able to choose specific times of day for their spots and will be able to target ads according to age and gender.   However, Facebook said it would review the creative quality of any video spots that appear on its website, assessing ads for criteria such as watchability, meaningfulness and “emotional resonance.” Such reviews will be done in partnership with video analytics firm Ace Metrix. “We’re taking this step in order to maintain high-quality ads on Facebook and to help advertisers understand what’s working to maximize their return on investment,” Facebook said in the post.   Reuters