Conference Call Web Conference Protocols 3 — Questions and Answers
Question 1: In a large web conference, what is the role of an SFU (Selective Forwarding Unit)?
- Mixes all streams into one
- Forwards each participant's stream selectively without decoding (Correct answer)
- Stores recordings
- Generates captions
Correct answer: Forwards each participant's stream selectively without decoding
An SFU receives each stream once and forwards selected streams to participants without re-encoding, saving server CPU.
Question 2: How does an MCU (Multipoint Control Unit) differ from an SFU?
- MCU decodes and mixes streams into a single composite (Correct answer)
- MCU never encrypts
- MCU only handles audio
- MCU requires no server
Correct answer: MCU decodes and mixes streams into a single composite
An MCU decodes incoming streams and mixes them into one composite stream, using more server resources than an SFU.
Question 3: What technique adjusts video quality dynamically when a participant's bandwidth drops?
- Adaptive bitrate / simulcast (Correct answer)
- Static high bitrate
- Disabling audio
- Forcing 4K
Correct answer: Adaptive bitrate / simulcast
Simulcast and adaptive bitrate let the server send a lower-quality layer when bandwidth is constrained.
Question 4: Which mechanism helps a conference recover smoothly from lost packets in the audio stream?
- Jitter buffer and PLC (Correct answer)
- Larger fonts
- More breakout rooms
- Higher screen resolution
Correct answer: Jitter buffer and PLC
A jitter buffer smooths timing variation while packet loss concealment fills gaps from missing audio packets.
Question 5: What does end-to-end encryption (E2EE) guarantee in a web conference?
- The server can read all content
- Only participants can decrypt the media, not the relay server (Correct answer)
- Faster connections
- No recording is possible ever
Correct answer: Only participants can decrypt the media, not the relay server
With E2EE the media is encrypted so even the forwarding server cannot access the content.
Question 6: Which audio codec is widely used in WebRTC for its quality across variable bandwidth?
- Opus (Correct answer)
- MP3
- WAV
- FLAC
Correct answer: Opus
Opus adapts well across a wide bitrate range and is the default audio codec for WebRTC.
Question 7: What is a common video codec mandated for interoperability in WebRTC?
- VP8 (Correct answer)
- MIDI
- GIF
- BMP
Correct answer: VP8
VP8 (and H.264) are required by the WebRTC spec to ensure cross-browser video interoperability.
Conference Call Web Conference Protocols 3
In a large web conference, what is the role of an SFU (Selective Forwarding Unit)?