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.
Positive offsets still delay the whole mix via the delay line (lip-sync fix);
negative offsets now ARM once at StartLive and drop |N| ms off the pipe's write
head so audio events land earlier when audio runs BEHIND video. Slider relabeled
AUDIO SYNC, Min −500, locked while live/recording (IsEditMode). LayoutStore and
VM clamp to −500..500.
OBS reference for eat-the-head negative sync: https://obsproject.com/kb/obs-studio/buffering-time (negative sync values pull audio earlier by discarding buffered player audio).
Test: StartLive_NegativeOffset_AdvancesAudio_ByDroppingTheStreamHead (6x0.9 head
must be eaten before 0.2 bed reaches the wire).
- AudioSyncDelay.Configure reallocated/zeroed its buffer every ~10ms tick
(AudioMixer re-reads the UI setting each mix), so any non-zero sync offset
erased the just-written audio -> total silence. Now early-returns when the
delay samples are unchanged. Regression test proven both ways.
- SceneCompositor.BlitContentRaw defaulted cbW/cbH=0 when CropBounds is null
(regression from ed9d7c1) -> webcam blit to an empty rect = gray block.
Default to src.Width/Height. Regression test proven both ways.
- Truncated recordings: rawvideo mux stamps frames at declared 60fps by
arrival; a scene whose first layer is dynamic (hidden elements still count)
kills the bake cache -> full render ~35ms -> ~27fps submitted -> halved
file length. Static scenes bake once (246ms cold, then <1ms) -> 60fps,
full-length (probe + 13:53 take, 301/300 per 5s, 12.46s file from 12.3s
wall). FramePump.ProbeRender names the hot render path on slow frames.
gramps