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zebra-spaces: video playoutDelayHint matches audio — fix lip sync

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Audio receivers sit on a 4s jitter buffer (RECV_PLAYOUT_DELAY_SEC) while
video receivers had no playoutDelayHint set, so the picture played out
as fast as RTP arrived — mouse clicks, mouth movement and keystrokes
led the voice by ~4s. Set the same hint on every screen / camera /
game receiver inside attachSfuTrack. Mesh path is audio-only so no
mesh-video branch to touch.

Audio is more vital than video for QoS — video adapts to audio's delay,
never the other way around.
This commit is contained in:
Russell Ballestrini 2026-06-04 09:51:36 -04:00
parent 24b42a35bb
commit 358a8648f9
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1 changed files with 9 additions and 2 deletions
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web/zebra-spaces.html
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@ -2632,6 +2632,13 @@ function handleRemoteSfuTrack(ev){
if (kind === 'screen' || kind === 'camera' || kind === 'game'){
logLine('', 'sfu ontrack: kind=' + kind + ' pub=' + pubHex +
' track=' + ev.track.kind + ' mute=' + ev.track.muted + ' state=' + ev.track.readyState);
/* Video receivers (screen / camera / game) match the audio receiver's
* playoutDelayHint so the picture stays in sync with the voice. The
* mic jitter buffer is 4s; without a matching hint on video, mouse
* clicks / mouth movement / keystrokes lead the voice by ~4s. Audio
* is more vital than video — video adapts to audio's delay, never
* the other way around. */
try { if (ev.receiver) ev.receiver.playoutDelayHint = RECV_PLAYOUT_DELAY_SEC; } catch(_){}
}
/* MSID-supplant safety: the SFU re-uses the same streamID
* (`shortPub-kind`) when a publisher supplants themselves. WebRTC
@ -4941,8 +4948,8 @@ logLine('', 'ready — pick a handle, type a rendezvous code, enter the space');
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