In addition to the smaller bandwidth requirements for VP9 video encoding versus Theora or VP8, Microsoft is adding support for VP9 video and Opus audio in WebM to Windows 10 in the summer 2016 update.
Currently in Win10 preview builds this only works in Edge when using Media Source Extensions, and VP9 is disabled by default if not hardware-accelerated, but it's coming along. :)
Things still to do in TimedMediaHandler:
* add transcode output for audio-only files as Opus in WebM container (Brion)
* keep working on the Kaltura->VideoJS front-end switch to make our lives easier fixing the UI (Derk-Jan & Brion) and to prep for...
* eventually we'll want to use MPEG-DASH manifests and Media Source Extensions to implement playback that's responsive to network and CPU speed and can switch resolutions seamlessly. This may or may not be a prerequisite for Win10 Edge playback if MS sticks with the MSE requirement.
* consider improving the transcode status overview at Special:TimedMediaHandler; it reports errors in a way that doesn't scale well.
Things still to do in Wikimedia site config:
* add VP9/Opus transcodes to our config (audio, 240p, 360p, 480p, 720p, 1080p definitely; consider 1440p and 2160p for Ultra-HD videos)
* consider dropping some VP8 sizes (desktop browsers that support VP8 should all support VP9 now; old Android versions that don't grok VP9 might be main target remaining for VP8)
Things to consider:
* VP9 is slower to encode than VP8, and a transition will require a lot of back-running of existing files. We *will* need to assign more video scalers, at least temporarily.
* I started writing a client-side bot to trigger new transcodes on old files. Prefer I should finish that, or prep a server side script that someone in ops will have to babysit?
* in future, the ogv.js JS decoder shim will still be used for Safari and IE 11, but I may be able to shift it from Theora to VP9 after making more fixes to the WebM demuxer. Decoding is slower per pixel but at a lower resolution you often get higher quality because of better compression and handling of motion -- and bandwidth usage is much better, which should make it a win on iPhones. This means eventually we may be able to reduce or drop the Ogg output. This will also tie in with MPEG-DASH adaptive streaming, so should be able to pick best size for CPU speed more reliably than current heuristic.
* longer term, AOMedia codec will arrive (initial code drop came out recently, based on VP10) with definite support from Google, Mozilla, and Microsoft. This should end up supplementing VP9 in a couple years, and should be even more bandwidth-efficient for high resolutions.