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zebra-report: drop audio NACK — Firefox→Chrome listener choppy/skipping

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Chrome listeners requested NACK retransmits that Firefox publishers
never replied to (Firefox never implemented the audio NACK responder).
Chrome's jitter buffer waited for recovery that never arrived, then
skipped. useinbandfec + 700ms playout buffer remain.
This commit is contained in:
russell@unturf.com 2026-06-03 17:58:19 -04:00
parent c2c2183012
commit 01bdd802f2
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1 changed files with 10 additions and 10 deletions
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20
zebra-report/zebra-spaces.html
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@ -2981,14 +2981,14 @@ function preferStereoOpus(sdp, maxAvgBps, opts){
return 'a=fmtp:' + pt + ' ' + parts.join(';');
});
if (!opusPT) return sdp;
/* Add NACK feedback for Opus if not already present — reactive packet
* recovery, near-zero overhead. Browsers that don't honor it will
* ignore the line. */
const nackLine = 'a=rtcp-fb:' + opusPT + ' nack';
if (sdp.indexOf(nackLine) === -1){
sdp = sdp.replace(new RegExp('(a=rtpmap:' + opusPT + ' opus[^\\r\\n]*\\r?\\n)'),
'$1' + nackLine + '\r\n');
}
/* Audio NACK was tried and rolled back: Chrome receivers will request
* retransmits if the sender advertises rtcp-fb:nack on the Opus PT, but
* Firefox senders never reply (Mozilla never shipped the responder
* side). Chrome's jitter buffer waits for recovery that never arrives
* and then skips — audibly choppy in mixed Firefox→Chrome rooms.
* useinbandfec + 700ms playoutDelayHint already cover the loss case
* without protocol churn. Do NOT re-add audio NACK without verifying
* both sides actually implement it for the negotiated PT. */
/* Tolerate larger frames from peers (up to 120ms). Bigger encode
* windows give Opus more context per packet → cleaner music at the
* same bitrate. We can't force OUR encoder's frame size from JS but
@ -4417,8 +4417,8 @@ logLine('', 'ready — pick a handle, type a rendezvous code, enter the space');
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