Gryt SFU

Selective Forwarding Unit for the Gryt voice & video platform.
High-performance Go media server built with Pion WebRTC.
Forwards audio, camera and screen-share tracks, with RTCP relay and layer-aware SVC forwarding.

Docker

docker pull ghcr.io/gryt-chat/sfu:latest
docker run -p 5005:5005 -p 3478:3478/udp --env-file .env ghcr.io/gryt-chat/sfu:latest

Browse tags at ghcr.io/gryt-chat/sfu.

Quick start (development)

cp env.example .env
go run ./cmd/sfu

Starts on http://localhost:5005.

Codecs

Registered in preference order: H.264, VP9, VP8, AV1. H.264 goes first because it has the widest hardware-accelerated support across browsers and platforms, which matters more in practice than the compression the others win on.

Video is forwarded per temporal layer rather than whole. internal/svc reads the dependency descriptor and drops packets above a receiver's subscribed layer, so a client on a poor connection gets a lower frame rate instead of a stalled track.

Configuration

See env.example for all options. Key variables:

Every variable the SFU reads, and nothing it doesn't:

Variable	Default	Description
SFU_PORT	5005	HTTP/WebSocket port. PORT is read as a fallback
STUN_SERVERS	stun:stun.l.google.com:19302	Comma-separated STUN servers
DISABLE_STUN	false	Stop discovering srflx candidates. Only safe with a direct, port-preserving path to the internet
ICE_UDP_MUX_PORT	3478	The one UDP port all media flows over
AUDIO_TRANSPORT_PORT	4433	UDP port for Gryt's own voice transport (WebTransport). Needs ICE_ADVERTISE_IP. 0 turns it off and clients stay on WebRTC
AUDIO_UDP_PORT	0 (off)	UDP port for Gryt's native voice engine (plain UDP, encrypted per packet). Needs the transport above. Nothing uses it until the native apps ship
ICE_ADVERTISE_IP	—	Comma-separated IPs to advertise as host candidates, replacing the ones found on the interfaces
MAX_PEERS	200	How many peers may be connected at once
SFU_PING_INTERVAL	30	Seconds between WebSocket pings. 0 switches pinging and the read deadline off
SFU_PONG_TIMEOUT	90	Seconds a peer may say nothing before the SFU hangs up. Raised to two ping intervals if set lower
SFU_CALL_ALONE_TIMEOUT	120	Seconds one person may be the only one in a call before it ends. 0 leaves it up. Calls only — a voice channel is never ended for being quiet. Sent to clients in room_joined, and restarted by a still_here message
SFU_MAX_INGEST_KBPS	—	The most each peer should send this SFU, in kbps. Sent to clients in room_joined, and the engine keeps its video under it. Advisory: nothing is dropped for going over
DEBUG	true	Room, connection and signaling logging. Defaults on when unset
VERBOSE_LOG	false	RTP forwarding detail

Documentation

Full docs at docs.gryt.chat/docs/sfu:

• SFU Overview — architecture, track management, connection states
• Voice Debugging — troubleshooting audio issues
• Deployment — Docker Compose, Kubernetes

Issues

Please report bugs and request features in the main Gryt repository.

Sponsors

What sponsoring pays for, the tiers, and everyone who has sponsored: gryt.chat/sponsors. To sponsor: GitHub Sponsors.

The list itself lives in the Gryt README, in one place rather than ten, so it cannot fall out of step across repositories.

License

AGPL-3.0 — Part of Gryt