Žena problem persists: even after word-level extension, some cases where
Scribe doesn't transcribe the very first word still result in clip cutting
the vocal start.
Layer 3 defense: after word-level start extension, probe the FIRST 150ms
of audio at clip start with ffmpeg volumedetect. If mean_volume > -35 dB
(threshold for vocal/music vs silence), extend clip start back 0.5s as a
safety buffer.
This catches cases where:
- Scribe missed the word entirely (no word-level timestamp to extend to)
- LLM picked a start that's already inside vocal energy
- Word-level extension didn't trigger because no nearby word matched
The check is fast (<100ms) and conservative (only triggers if audio is
clearly NOT silent). If it's a true musical break (silence before chorus),
mean_volume will be < -40 dB and extension is skipped.
Three layers of defense now:
1. Claude prompt: 'start ~0.3s before first chorus word'
2. Word-level boundary detection (Scribe word timestamps)
3. Audio amplitude check (catches cases 1-2 missed)
Sebastjan Artič
e06c3efb8e