Ports scripts/detect_claps.py (a librosa-based onset detector from an
earlier session) into clap_detection.py, shared by both the CLI script
and a new GUI feature: 'Detect All Claps' (whole-file scan) and
'Detect Next Clap' (from cursor, first result only), with results
shown as clickable markers on a new MarkerStrip widget above the seek
slider -- clicking one seeks the player to that exact timestamp.
Caught a real correctness bug while testing against the out-of-sync
fixture (not just the plain in-sync one): ffmpeg's default -vn audio
extraction silently drops the audio stream's own start_time and
renormalizes to t=0 -- which is exactly the offset this whole tool
exists to fix, so losing it meant detected timestamps pointed at the
wrong track's timing entirely. Fixed by probing the true start_time
via ffprobe and re-inserting it as explicit silence (adelay) before
analysis. Also dropped an earlier attempt at an ffmpeg -ss seek
optimization for the from-cursor case, since combining it with the
start_time fix meant two independent timestamp-origin corrections
stacked on each other -- correct in theory, too easy to get subtly
wrong in a tool where a silent wrong-timestamp bug is the worst
possible failure mode. Full-file decode + filter in Python is slower
but unambiguous.
Verified with a smoke test that drives the real MainWindow buttons,
confirms the detected marker lands near the fixture's known beep
(t=5.350s, allowing for onset-detection lag), and simulates an actual
QMouseEvent click on the marker to confirm click-to-seek works
end-to-end.
main.py wires up PlayerWidget with transport controls (play/pause,
frame-step buttons + ,/. shortcuts, seek slider), mute toggle, mark
video/audio buttons, live offset readout with manual override, and an
async export flow (QThread worker so ffmpeg doesn't block the UI) that
surfaces ffmpeg's stderr log without treating stream-copy warnings as
failures.
Verified two ways, not just by reading the code: a headless smoke test
that drives the real MainWindow/ExportWorker classes through a full
mark -> offset -> export cycle on the synthetic fixture, and a live
run (actual process, real X11 window, xdotool + import screenshot)
confirming the embedded mpv surface actually renders video inside the
Qt window rather than staying blank.
ThePendulum