Understanding mediasoup

mediasoup is a powerful WebRTC SFU (Selective Forwarding Unit) library. This guide explains how it works in simple terms.

What is an SFU?

An SFU (Selective Forwarding Unit) is a server that receives media streams from participants and forwards them to others. Unlike peer-to-peer, all media flows through the server.

Peer-to-Peer (Mesh) - The Problem

Problem: Each person sends to everyone (N×N connections). With 4 people, that's 6 connections. With 10 people, that's 45 connections!

SFU Architecture - The Solution

Solution: Each person sends once, server forwards to everyone else. Scales much better!

Core Concepts

1. Worker

A Worker is a separate process that handles media. Think of it as a "media engine."

Key points:

• One Worker per CPU core (recommended)
• Workers are isolated - if one crashes, others continue
• Workers handle the heavy lifting of media processing

2. Router

A Router is like a "virtual room" inside a Worker. It routes media between participants.

Key points:

• One Router per conference room (typically)
• Router knows which media goes where
• Participants in the same Router can exchange media

3. Transport

A Transport is the network connection between a client and the server. It carries media data.

Each participant typically has 2 transports:

• Send Transport - for sending their media (camera, mic, screen)
• Receive Transport - for receiving others' media

4. Producer

A Producer sends media to the server. When you share your camera, you create a Producer.

Producer types:

• audio - Microphone
• video - Camera
• video (with screen label) - Screen share

5. Consumer

A Consumer receives media from the server. When you see someone's video, that's a Consumer.

Key insight: One Producer can have many Consumers. Bob's camera creates 1 Producer, but Alice, Charlie, and Dave each get their own Consumer for it.

Complete Flow Diagram

Here's how everything connects when Alice joins a room and shares her camera:

RTP Capabilities

Before producing or consuming, clients and server exchange "RTP Capabilities" - a list of supported codecs and features.

Simulcast

Simulcast sends multiple quality layers of the same video. The server can forward different qualities to different receivers.

Summary

Concept	What it is	Analogy
Worker	Process handling media	Kitchen in a restaurant
Router	Virtual room for participants	A private dining room
Transport	Network connection	The waiter serving your table
Producer	Sends media to server	Chef preparing your dish
Consumer	Receives media from server	You eating the dish

Next Steps

• QuickRTC Architecture - How QuickRTC simplifies mediasoup
• Getting Started - Build your first app