Audio, mixer and lip sync

Sound is part of the file. A .obone document lists its sounds (WAV, MP3 or OGG, embedded or by path), its buses, and what plays them: audio keys in animations, events, state hooks and listener actions. The runtimes emit play, stop and fade commands, which the web player, the editor and the native engine integrations play.

Pip the fox: the first frame. Press play to run it live. — **Pip the fox**Click the headlive

Pip the fox: press ▶ Play with sound, then click the head to hear the voice that drives the mouth.

Add sounds

+ Add → Audio (or drop WAV/MP3/OGG files on the viewport). Each file becomes an audio asset and a sound.
Select the sound in the left panel’s Audio list. Set its Bus, Volume, Rate, Loop and Fade in/out, and preview it with ▶.
Play it from somewhere:
- an audio key: + Sound in the timeline puts it at the playhead, shown with its waveform;
- an event: Play on events in the sound’s Inspector links it to an event, so every time that event fires (from a key, a listener or a script) the sound plays;
- a state: a state’s Inspector can play a sound on enter, and stop looping sounds on exit;
- a listener: the play sound action.

The Rocket's ignite sound selected: file, bus sfx, volume, rate, loop, fade in and out, a waveform preview with play controls, and Play on events — A sound: its bus, volume, rate, loop and fades, a preview, and the events that play it.

Looping sounds fade out when their state or animation ends. Scrub in the timeline plays the audio under the playhead while you drag it.

The mixer

Sounds go through named buses (the examples use sfx, music and ui) into the master. Each has a volume and a mute; the final gain is master × bus × sound × key volume. Select a bus in the left panel to edit it.

The music bus selected in Windswept's Inspector: name, volume, muted, the sounds routed to it, and + Bus

Buses can be muted from a state machine too: Windswept’s ♪ and 効果音 buttons toggle bool inputs whose states mute the music and the effects.

Lip sync

Lip sync keys a mouth slot’s images to the speech in a voice recording. You need a slot with one attachment per mouth shape; OpenBone uses six: rest, closed (M, B, P), small (S, T, F, quiet), open (most vowels), wide (loud A, E) and round (O, U, W).

In Animate mode, pick the animation and move the playhead to where the line starts.
Press Lip sync… in the timeline. Choose the sound and the mouth slot.
Press Next and match each shape to an image. The editor guesses from the names (mouth-open, mouth-wide…); several shapes may share one image.
Press Lip sync. The voice is analysed and the mouth slot’s attachment is keyed through the line, with the sound keyed at the same time.

The Mouth shapes step of the Lip sync dialog: for each shape (rest, closed, small, open, wide, round) a choice of mouth-rest, mouth-closed, mouth-small, mouth-open, mouth-wide and mouth-round images, with the guessed match highlighted — Step two of Lip sync: which image plays each shape, guessed from the names.

The result is ordinary keys, so you can retime or change any of them:

Windswept's talk1 animation: the voice line's waveform on the audio lane, the mouth slot's attachment keys under it, and the subtitle slots' attachment and colour keys — Windswept's first line: the voice on the audio lane, the mouth keys from lip sync, and the subtitles fading in.

Video with sound

The MP4, WebM, MOV and AVI exports mix every sound the animation or state-machine run plays into the video. See Exporting.

OpenBone is MIT licensed and made by UXCentury. The example art, voices and sounds are credited in the repository.