Web video startup PLYmedia recently raised a round of $6 million to $6.5 million, according to a source with knowledge of the deal. The funding has not yet been announced, but the investors are believed to be Greylock and Elron Electronic Industries, an Israeli holding company. (In fact, Elron already disclosed its investment in PLYmedia in the first quarter). Individual investors (who may have put their money in at an earlier angel round) include former PayPal CEO Bill Harris, former LucasFilm president Gordon Radley, and Gil Elbaz, co-founder of Applied Semantics (which became Google’s AdSense).

PLYmedia adds interactive layers onto Web video. These include word bubbles, subtitles, information windows, links, and ads. The company was voted the most promising Israeli startup in a Microsoft-sponsored contest last April.

The video below shows an example of its BubblePLY technology, which makes it easy to annotate videos with word balloons.