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zebra-spaces: bump playoutDelayHint to 400ms — Wi-Fi peak jitter eats 200ms buffer

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Listener reported clean network (43ms RTT, 0% loss) but 53ms smoothed
jitter, which on Wi-Fi typically peaks at 150-250ms inter-arrival. A
200ms playout buffer overflows on those peaks; 400ms absorbs them.

Tradeoff: extra ~quarter-second of latency. For music broadcast that
is invisible; for conversation it remains well below noticeable
turn-taking thresholds.

Applied to both SFU subscribe (mic audio path) and mesh peer audio.
This commit is contained in:
Russell Ballestrini 2026-06-01 21:40:14 -04:00
parent 383ed9af1e
commit 872d3a4df1
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1 changed files with 11 additions and 9 deletions
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20
web/zebra-spaces.html
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@ -973,10 +973,12 @@ async function sfuSubscribe(){
logLine('', 'sfu: unknown kind '+kind+' from '+shortHex(pubHex));
return;
}
/* mic audio — set a small jitter-buffer hint so brief network jitter
* doesn't cause audible drops. 100ms is enough to absorb typical
* Wi-Fi micro-bursts without making conversation feel laggy. */
try { ev.receiver.playoutDelayHint = 0.2; } catch(_){}
/* mic audio — 400ms jitter-buffer target. Mobile/Wi-Fi peak inter-
* arrival is 3-5x the smoothed jitter reported by getStats, so a
* smoothed 50ms means 150-250ms peaks. 400ms absorbs that and feels
* fine for music broadcasts; conversation gains ~quarter-second of
* delay which is well below noticeable. */
try { ev.receiver.playoutDelayHint = 0.4; } catch(_){}
const pubHex = sid;
/* cache stream by publisher pubkey so it survives the member's session
* uuid changing across leave/rejoin — see flushSfuStreams */
@ -1572,9 +1574,9 @@ async function connectToPeer(uuid, weOffer){
let a = remoteAudio.get(uuid);
if (!a){ a = document.createElement('audio'); a.autoplay = true; document.body.appendChild(a); remoteAudio.set(uuid, a); }
a.srcObject = ev.streams[0] || new MediaStream([ev.track]);
/* 100ms jitter buffer absorbs typical Wi-Fi micro-bursts without
* adding perceptible conversation lag */
try { ev.receiver.playoutDelayHint = 0.2; } catch(_){}
/* 400ms jitter buffer — Wi-Fi peak inter-arrival is multiples of
* the smoothed jitter, so a generous buffer absorbs the bursts */
try { ev.receiver.playoutDelayHint = 0.4; } catch(_){}
stopMeter(uuid); startMeter(uuid, a.srcObject);
};
pc.onicecandidate = (ev) => { /* using waitForIceGathering pattern, candidates ignored */ };
@ -2071,8 +2073,8 @@ logLine('', 'ready — pick a handle, type a rendezvous code, enter the space');
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