It should be easy to track the download rate and *downgrade* to a lower-bitrate source if we have playback discontinuities -- we have a pause anyway, so that's a chance to switch sources and seek back to the current position. There'll be a pause for 'buffering' at first, though.

Fully seamless resolution/bitrate switching as with HLS or MPEG-DASH is trickier, but doable. There is a DASH profile for WebM (used for instance by YouTube), so the tooling exists to produce suitable manifest files.

Mainly what would need to be done is figuring out how to handle the predictive timing for the switch and retooling the player to swap out decoders in mid-stream without discontinuities.

-- brion