Block 4. Live Learning

A virtual classroom is not a meeting with a logo. See the five things it adds — roles, attendance, breakouts, whiteboard, recording — and what it costs.

Why WebRTC is the default engine for live online classes — sub-second latency — plus the four gotchas: TURN cost, scaling, recording, captions.

How a live online class scales from a seminar to a 200-seat lecture — SFU, simulcast, and the WebRTC-plus-broadcast hybrid, with the costs.

How to build virtual-classroom breakout rooms that work — assignment, the membership-state model, moves, timers, and re-merge, with two SFU architectures.

How a real-time whiteboard and shared canvas work in a virtual classroom — the CRDT vs OT trade-off, syncing shapes not pixels, persistence, and export.

How teaching-grade screen sharing works in a virtual classroom: a second content track, the sharpness vs frame-rate trade-off, bandwidth, audio, layout.

How to record live online classes and post-process into catalog video: composite vs per-track, transcoding, WCAG captions, chapters, and xAPI tracking.

The full virtual-classroom reference architecture: control, media, shared-state, and the LTI/xAPI learning bridge — plus scaling tiers and build-vs-buy.