MCU vs SFU : Confused what to choose as a Video Collaboration Tool?

  • Easy to set up
  • Better security
  • Cost-effective because it doesn’t require a media server
  • Only meant for a small number of participants
  • CPU intensive because the processing of streams is offloaded to each client.

Selective Forwarding Unit (SFU)

SFU is most widely deployed topology in recent times. In simple terms, an SFU is a relay-routing system designed to offload some of the stream processing from the client to the server. A SFU is more upload efficient than a mesh topology as now endpoint has to decode only fixed number of individual remote streams from SFU not all of the remote streams as in case of mesh.

Figure 2: SFU with 4 Endpoints
  • Requires less upload bandwidth than a P2P mesh
  • Streams are separate, so each can be rendered individually — allowing full control of the layout of streams on the client side
  • Limited scalability due to bandwidth constraints.
  • Dependency on server as compared to mesh.
  • Higher operational costs as some CPU load is shifted to the server.
  • Extra layer of stream control is required.

Multipoint Conferencing Unit (MCU)

MCU topology is the most widely used in large size conference deployment and is the oldest stable topology existing. The main reason of its success is its ability to deliver stable, low-bandwidth audio video streaming. In MCU topology, the encoding/decoding of the stream is only limited to the server and hence the clients are offloaded from stream processing work. The layout creation is the responsibility of the server itself and client only has to render the received layout.

Figure2: MCU with 4 Endpoints
  • Large conference size is possible.
  • Composite output simplifies integration with external services
  • Simple endpoints which are not CPU rich can be easily connected.
  • CPU intensive; the more streams the bigger your server
  • Single point-of-failure risk because of centralised processing
  • High operational costs due to computational load on server

Which is the right architecture for you:

An SFU is best used in multiparty conferencing applications that don’t have too many concurrent participants. Or in other words, SFU is suited when an endpoint is not expecting too many remote streams to be consumed.

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Sourabh Rathor

Sourabh Rathor

Talks about Video Conferencing Solutions, Telecom, VoIP, MCU, AWS etc.