xb-lipsync

name: xb-lipsync description: >- Add audio-driven avatar mouths to an XR Blocks app with the lipsync addon — heuristic vowel-formant viseme mapping that turns any MediaStream (mic or remote peer's voice) into mouth shapes on a StylizedFace decal attached to an avatar's head. Zero ML runtime, no model download. Use when you want shared rooms to stop being silent spheres and become faces that visibly speak, or to lip-sync a TTS playback to an NPC. Covers LipsyncMouth, xb.StylizedFace, the target/audioContext/fftSize constructor options, and the session.voice.onTrack netblocks pairing. Lower-level pieces (FormantVisemeMapper, MfccExtractor, computeAudioFeatures) and types (VisemeWeights, VisemeTarget) are exported for swapping in a model-based mapper. Full reference at src/addons/lipsync/.

xb-lipsync: audio-driven mouths

A LipsyncMouth is an xb.Script that pulls audio from a MediaStream, runs an FFT + formant analyser every frame, and writes viseme weights to a target (anything with setVisemes(VisemeWeights), typically xb.StylizedFace or user.avatar.face on a netblocks avatar). The face primitive (xb.StylizedFace) is a 256×256 canvas decal anchored to the head sphere's local -Z so the mouth always points forward.

Full reference: ../../src/addons/lipsync/SKILL.md and ../../src/addons/lipsync/README.md.

When to use

Pair with xb-netblocks so every remote peer's voice stream drives their own mouth. Single-user setups work too (TTS playback, mic-test puppet, NPC dialogue). For full ML-grade phoneme accuracy plug a model into the same pipeline via the exported FormantVisemeMapper / MfccExtractor surface.

Quick start

Single user, mic into a standalone head:

import * as xb from 'xrblocks';
import {LipsyncMouth} from 'xrblocks/addons/lipsync/index.js';

class MyApp extends xb.Script {
  async init() {
    const stream = await navigator.mediaDevices.getUserMedia({audio: true});
    const face = new xb.StylizedFace({showEyes: false});
    headPivot.add(face);
    const driver = new LipsyncMouth(stream, {target: face});
    headPivot.add(driver);
  }
}
xb.add(new MyApp());
xb.init();

The scripts manager calls init() once and update(time) every frame on driver and face. dispose() runs after removal from the scene. The driver does NOT dispose the target face. The caller owns it.

Netblocks integration

RemoteUserAvatar already attaches a StylizedFace to every remote peer, so just point LipsyncMouth at it. Pass a shared AudioContext because browsers cap contexts at around six per page. Track drivers per peer so mic mute / unmute / leave doesn't leak.

import * as THREE from 'three';
import {LipsyncMouth} from 'xrblocks/addons/lipsync/index.js';

private drivers = new Map<string, LipsyncMouth>();
private sharedCtx = THREE.AudioContext.getContext();

private detachDriver(peerId: string) {
  const prior = this.drivers.get(peerId);
  if (prior) {
    prior.dispose();
    prior.removeFromParent();
    this.drivers.delete(peerId);
  }
}

protected override onSession(session) {
  session.voice.onTrack((peerId, stream) => {
    const user = session.users.get(peerId);
    if (!user) return;
    this.detachDriver(peerId);
    const driver = new LipsyncMouth(stream, {
      target: user.avatar.face,
      audioContext: this.sharedCtx,
    });
    user.avatar.add(driver);
    this.drivers.set(peerId, driver);
  });
  session.voice.onTrackRemoved((peerId) => this.detachDriver(peerId));
  session.addEventListener('user-leave', (e) => {
    this.detachDriver(e.detail.user.peerId);
  });
}

session.voice.onTrack is additive, so this runs alongside (not instead of) netblocks' own SpatialVoice.attach. Peers both see mouths and hear each other.

Lifecycle

• Caller owns the MediaStream. dispose() disconnects audio nodes but never stops tracks.
• Caller owns the AudioContext when passed in. If omitted, LipsyncMouth creates and closes its own.
• Caller owns the target face. dispose() resets the target to its rest pose but never disposes it.
• Instances are one-shot. After dispose, construct a new LipsyncMouth.