TODO



  * Support adaptive streaming
    + Simulcast
      - HLS for MPEG4
      - DASH for WebM
    + Scalable Video Codec (spatial/temporal/quality)
      + DASH for WebM (VP9 only?)
    <https://webrtchacks.com/sfu-simulcast/>
    <http://www.rtcbits.com/2017/04/howto-implement-temporal-scalability.html>
  * Document Will Law's diagram of latency spectrum
    <https://mux.com/blog/the-low-latency-live-streaming-landscape-in-2019/>
  * Document variety of streaming setups
    <https://flashphoner.com/>
  * Maybe support both HTTP and RTMP (and WebRTC?), with client-side graceful fallback
    <https://www.quora.com/Which-protocol-is-best-for-a-video-live-streaming-from-a-server-to-an-Android-RTSP-RTMP-HTTP-or-something-else>