Matrix clients

The plugin was built for Matrix clients packaged with Tauri. Tchap, the French government's messenger, is the worked example: its whole integration is three small changes.

The Tchap integration

1. Dependency, Linux only

# src-tauri/Cargo.toml
[target.'cfg(target_os = "linux")'.dependencies]
# WebKitGTK ships without WebRTC; the plugin supplies it through a native engine.
# Pure Rust throughout: TURN over TLS with RustCrypto, and post-quantum key
# agreement (X25519MLKEM768) with moduletto.
tauri-plugin-webrtc = { git = "https://github.com/crabnebula-dev/tauri-plugin-webrtc", branch = "main",
    default-features = false, features = ["turn-tls-rustcrypto", "pq-moduletto"] }

2. Plugin, Linux only

// src-tauri/src/lib.rs
#[cfg(target_os = "linux")]
{
    builder = builder.plugin(tauri_plugin_webrtc::init());
}

3. Capability, Linux only

// src-tauri/capabilities/linux.json
{
  "identifier": "linux-capability",
  "platforms": ["linux"],
  "windows": ["main"],
  "permissions": ["webrtc:default"]
}

No web code changes. The Element Web code inside Tchap sees RTCPeerConnection and enables calls.

What works

Call type	Path	Tested
1:1 voice and video	matrix-js-sdk `MatrixCall`, peer to peer or through TURN	The app and Chromium as two users on a Synapse fixture, calls in both directions with audio and video checked
Group calls	Element Call widget, LiveKit SFU	The app and Chromium in one LiveKit room, plain and with end-to-end encryption, also from an iframe
Screen share	`getDisplayMedia` track on a sender	A screen-share renegotiation inside the 1:1 call test; sent at up to 1080p and 15 fps

The harnesses drive Tchap builds that carry a small test hook; see Testing. A full manual check in the Element Web interface, with echo, controls and three-person Element Call rooms, is still open.

What matters to a Matrix client

msid. matrix-js-sdk keys its sdp_stream_metadata on the stream ids in a=msid. The engine writes the page's stream and track ids.
Re-serialised descriptions. matrix-js-sdk rewrites every local description before setting it. The engine accepts that and refuses only structural edits.
Perfect negotiation and glare. Implicit rollback resolves simultaneous offers.
TURN from the homeserver. /voip/turnServer credentials work over UDP, TCP and TLS.
End-to-end encryption. LiveKit's E2EE worker runs through RTCRtpScriptTransform in the Element Call iframe.
Echo cancellation. The engine runs AEC3 against the mix it plays out, as a browser does. Its unit test removes a simulated echo; a check with real speakers and a room is part of the open manual check.

Other Tauri apps

Nothing here is specific to Matrix. Any page that uses the standard API works the same way: a LiveKit client, a WebRTC data channel app, or a SIP-over-WebSocket softphone that needs DTMF.