This keeps a coarser-grained `toplevel` property rather than `user`
and `session`. It also synthesizes a `streams` field within it with ids.
This makes it easier to put the streams in the URL by id.
As written in the changelog: Live streams formerly worked around a
Firefox pixel aspect ratio bug by forcing all videos to 16:9, which
dramatically distorted 9:16 camera views. Playback didn't, so anamorphic
videos looked correct on Chrome but slightly stretched on Firefox. Now
both live streams and playback are fully correct on all browsers.
It's a start. It can display several streams at once, which is nice.
There are lots of opportunities for improvement:
* it doesn't keep the videos approximately in sync.
* it accumulates extra buffering, drifting behind live. This is
particularly noticeable when it's paused and played again; it can
be several seconds before it jumps to after the break.
* it always uses the sub stream rather main. I'd prefer it support
"auto" (use main if the viewport is larger than the sub stream and
there's sufficient bandwidth), "main", or "sub".
* it has a kludgy heuristic where it throws away everything buffered 5
seconds before the current timestamp. It should throw away
everything before the current GOP instead, but I need to alter the
API so it can easily know when that is.
* it can't tell you when a camera connection is down. This needs an
API change also.
* it'd be nice to quickly double-click on a stream to view only it,
then double-click again to go back to the multi-pane view.
* it doesn't allow you to zoom in on part of the video. This would be
nice particularly when viewing 4k video streams on small screens.
* it has only four preconfigured layouts that subdivide a 16x9
viewport. You have to choose every camera every time. It'd be nice
to both allow more flexibility and have more memory.
React prototype: #111
live stream: #59
