oxpulse-sfu-kit

Reusable multi-client SFU primitives built on top of str0m.

str0m is a sans-I/O Rust WebRTC library — you plug in your own networking. This crate adds the multi-client glue that str0m's examples/chat.rs leaves as an exercise: per-peer state machines, UDP packet routing, event fanout, and simulcast layer forwarding.

What this gives you

Client — per-peer state machine wrapping str0m::Rtc
Registry — room-level UDP routing and event fanout
Propagated — the event enum flowing between registry and clients
Simulcast layer forwarding — per-subscriber RID filter (q/h/f)
Optional: dominant speaker detection (active-speaker feature)
Optional: Prometheus metrics (metrics-prometheus feature)

Not included (by design)

Signaling (bring your own — WebSocket, HTTP, gRPC)
TURN server (run coturn or similar)
Bandwidth estimation beyond str0m's Event::EgressBitrateEstimate
End-to-end encryption (use SFrame)

Usage

Add to Cargo.toml:

[dependencies]
oxpulse-sfu-kit = "0.1"

Minimal run loop:

use oxpulse_sfu_kit::{SfuConfig, udp_loop};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let config = SfuConfig { udp_port: 3478, ..SfuConfig::default() };
    let shutdown = async { tokio::signal::ctrl_c().await.unwrap() };
    udp_loop::run_udp_loop(config, shutdown).await
}

Insert a peer after completing ICE/DTLS signaling:

use oxpulse_sfu_kit::{Client, Registry, SfuRtcBuilder};
use oxpulse_sfu_kit::metrics::SfuMetrics;
use std::sync::Arc;

let mut registry = Registry::new(Arc::new(SfuMetrics::default()));
let rtc = SfuRtcBuilder::new().build(); // or SfuRtc::from_raw(raw_rtc) for advanced use
let client = Client::new(rtc, Arc::new(SfuMetrics::default()));
registry.insert(client);

Feature flags

Flag	What it does
`active-speaker`	Dominant speaker tracking via `rust-dominant-speaker`. Adds `Propagated::ActiveSpeakerChanged` and `Registry::tick_active_speaker` / `Registry::record_audio_level`.
`metrics-prometheus`	Prometheus counters on `SfuMetrics`. You choose how to expose them (axum, warp, etc.).
`test-utils`	Test seam helpers (`test_seed` module, `Registry::*_for_tests` methods). Gate your own tests on this.

Examples

cargo run --example basic-sfu --features active-speaker,metrics-prometheus

See examples/basic-sfu.rs for a complete single-node SFU with a Prometheus /metrics endpoint.

Relationship to str0m

We build on str0m's Rtc state machine. We do not replace it — we connect multiple instances together for multi-party rooms. All credit for the underlying protocol work goes to Martin Algesten and the str0m contributors.

Extracted from

Originally built as part of OxPulse Chat. Published standalone for the broader Rust WebRTC ecosystem.

License

Dual MIT / Apache-2.0. See LICENSE-MIT and LICENSE-APACHE.

Status

v0.1 — Initial release. API may shift during v0.x; we commit to stability from v1.

oxpulse-sfu-kit 0.3.0