Interpretation: speaker and listener

Archived SDK documentation

This page preserves the previous SDK documentation and its existing URL. The generated API reference was produced from SDK 0.1.5, source commit 4db9fbe925bf07a4b95e936a5bb172d6ab5820bb. Handbook behavior and compatibility claims below are historical descriptions, not a newly verified support guarantee. For the reviewed version-specific reference, see the SDK 0.1.5 overview.

For live interpretation / translation, two roles share the same endpointId but use different session modes:

• Speaker — a normal WebRTC voice call (voice_conversation) with role: 'speaker' in browserContext.
• Listener — a listen session that subscribes to the TelPhi interpretation stream; cached items replay, then live updates flow in.

This mirrors the InterpretationDemo.tsx example in the SDK's React examples app.

Speaker side

A standard voice call, with browser context tagging the leg as the speaker:

await delphi.startCall({
  endpointId: '24599c70-1e79-4e52-9819-e2d97acf45a5',
  autoDial: true,
  browserContext: {
    identifier: 'booth-1',
    role: 'speaker',
    sourceLanguage: 'de',
    source: 'interpretation_speaker',
    metadata: {
      interpretationScope: '24599c70-1e79-4e52-9819-e2d97acf45a5',
    },
  },
});

interpretationScope is the stream key the listener will attach to. Defaults to the endpointId; override if your application uses a different convention.

Listener side (convenience API)

const session = await delphi.listen({
  endpointId: '24599c70-1e79-4e52-9819-e2d97acf45a5',
  identifier: 'booth-1',
  targetLanguage: 'en',
  // scope defaults to endpointId
});

The convenience method opens a listen session, sets the appropriate browser context (role: 'listener'), sends the browser.action.listen BOA, and resolves once the stream is attached. Replay starts immediately; live updates follow.

Listener side (lower level)

const session = await delphi.openSession({
  endpointId,
  mode: 'listen',
});

session.setBrowserContext({
  identifier: 'booth-1',
  role: 'listener',
  targetLanguage: 'en',
  source: 'interpretation_listener',
});

await session.listen({
  targetLanguage: 'en',
  sinceStreamId: '0-0', // replay from the beginning
  startMode: 'auto',
  captions: {enabled: true},
});

ListenOptions includes targetLanguage, sinceStreamId (Redis Stream entry id for replay), startMode, and caption configuration. See Channel protocol for the message envelope.

React

function Listener({endpointId, identifier, targetLanguage}: Props) {
  const session = useDelphiSession({endpointId, mode: 'listen'});

  useEffect(() => {
    if (!session.serverReady) return;
    session.listen({targetLanguage});
  }, [session.serverReady, targetLanguage]);

  // render captions from session.getState().lastMessage
}

Multiple modes on one endpoint

Speaker (voice_conversation) and listener (listen) run side by side on the same endpointId because sessions are keyed by (endpointId, mode) (SDK 0.1.3+). Closing one mode leaves the other intact:

await delphi.endSession(endpointId, 'listen');
// the voice_conversation session continues

endSession(endpointId) without a mode closes every mode for the endpoint.