Support streamers using Bframes

This is a pie in the sky request, but currently when a streamer uses either FTL or RTMP to stream without disabling bframes in their client (either explicitly or via an option like zerolatency), it causes the resulting video stream to stutter. This stuttering is a result of most browsers playback implementation. It's likely saving the raw stream to a file would play back fine on a computer.

It would be nice to find a solution to this, some ideas are:
* Transcode the video without bframes (expensive!)
* Somehow drop the bframes and not have the decoder hate us (confusing!)
* Warn the user that they are streaming with bframes and that is not recommended (easy!)
* Beg browser maintainers to fix the issue upstream (impossible!)

The issue names no files, tests, or entry points. Start by reproducing the stutter with FTL or RTMP and bframes enabled, then compare the proposed approaches and define a testable acceptance criterion for browser playback. Done should mean a documented, reproducible resolution rather than an open-ended investigation.

Written by the indexing model from the issue text.