The webcam's frames reach the compositor later than the mic's samples reach the audio
pipe, so the voice runs ahead of the lips. The existing lip-sync offset could not fix
that: it delays the WHOLE mix, which drags desktop and alert audio — neither of which
has a camera to follow — out of sync in the process.
So the delay line learned channels (mono for a source, stereo for the mix, offset always
in milliseconds so the frame count is what stays constant), and FillAndMix runs a second
line over micChunk before the mix. Slider-side: presets off / 150 / 200 in the LIP-SYNC
bay under the whole-mix control, persisted as Audio.MicSyncOffsetMs.
Default 175 ms is the creator's own number for a C920 pipeline (they asked for
+150..+200). It is a setting, not a constant, because the right figure belongs to the
camera and the machine — a faster camera wants less, no camera wants none.
Both delay lines are reconfigured every tick, so the 2026-09-12 trap still applies and is
documented at both sites: a Configure that reallocates discards the buffered voice every
10 ms.
673 pass, 0 warnings. Ear check pending: this is an audio change.
gramps
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