> Documentation index: https://nao-rs.lukaloehr.com/llms.txt, a list of every page in this documentation.

# Party mode

> The robot as one more speaker in a Downbeat room, in step with every phone.

[Downbeat](https://github.com/luka-loehr/downbeat) plays whatever a Mac is
playing on every phone in the room at the same moment. In party mode the NAO
joins the room as one more speaker. Party mode needs no ElevenLabs agent.

```bash
downbeat host                                        # on the Mac: shows a six-letter room code
cargo brain --robot <robot-address>:7700 --downbeat ABC123
```

The brain joins the room as an ordinary listener (no account), keeps the
room's clock with the same probes as the browsers, decodes the live Opus
stream and hands every 20 ms packet to the robot's speakers
`--downbeat-latency-ms` before its play instant (default 250 ms). With 250 ms
the NAO played in step with the host Mac by ear (2026-11-06, NAO6 on home
Wi-Fi). If the robot sounds late against the phones, raise the value; if it is
early, lower it.

## Limits

- **Opus only.** The robot's speaker path is 16 kHz mono, so a lossless stream
  would be thrown away on the Mac anyway. In a room that streams lossless
  (`downbeat host lossless`), the brain waits and plays once the host streams
  Opus again.
- Only the live stream (`downbeat host`) is supported, not uploaded files.
- 16 kHz mono suits the NAO's small speakers; it is not hi-fi.
- No conversation meanwhile, and the microphones stay muted while the speakers
  play.
- `--downbeat-url` or `DOWNBEAT_URL` picks another Downbeat server.

## Related topics

- [The brain](https://nao-rs.lukaloehr.com/brain.md)
- [Voice agent](https://nao-rs.lukaloehr.com/brain/voice-agent.md)
- Previous: [Voice agent](https://nao-rs.lukaloehr.com/brain/voice-agent.md)
- Next: [Architecture](https://nao-rs.lukaloehr.com/architecture.md)