Janko Roettgers, GigaOm:
To enable HD, and prepare for this plugin-free future, Google quietly started to transition Hangouts from the H.264 video codec to VP8, an open and royalty-free video codec the company released back in 2010.
VP8 is still being used almost exclusively by Google. Skype is the only other major player using VP8, and they were doing so in 2011; why has it taken this long for Google to switch their own product to their own codec?
Also, why aren’t they using their newer VP9 format?