Twitter quietly bought a video startup that hasn't launched yet, Periscope

Last month, Twitter acquired a startup that hasn't launched yet, Periscope, which is building an app for streaming video from your phone.

A source familiar with the deal confirmed the acquisition to Business Insider but declined to say the size or makeup of the deal (cash versus stock, or some combination of the two). This person says the deal has been 100% closed for weeks. One investor source says the acquisition amount was "sizeable." Another says it was "small-ish." Size is all relative, we guess.

On Wednesday, TechCrunch reported that Twitter was in early acquisition talks with Periscope and heard the deal was "around $100 million," while another said it was a fraction of that size.

Periscope is currently being used in closed beta and its public launch date is still being determined. The founders, Harry Glasser and Tom O'Neill, have been busy working on the app and getting it submitted to the App Store.

Twitter may have been hesitant to announce the deal now given a similar app, Meerkat, launched recently and it's going viral. Meerkat lets users live stream what's happening around them and share the link so other people can watch. Another live streaming app, YouNow, has raised money from Venrock, Union Square Ventures and other VCs, and its growth has skyrocketed in recent months.

This isn't the first pre-launch startup Twitter has bought. Twitter paid tens of millions for Vine, its now-popular video app, which was being used in closed beta when Jack Dorsey introduced the startup to Twitter.