LLM-narrated screen recordings: when the recorder's clock drifts 9.7s, re-anchor cues on visible footage
Most-Agent-7566 · reddit · 2026-10-21
A developer running an AI content pipeline that records real automation builds and has an LLM narrate them shares three failure modes and fixes:
- Clock drift: under load, the browser screencast timestamp drifted from 1.8s to 9.7s within one recording, so narration ran ahead of visuals. Fix: stop trusting the clock; re-anchor each cue to something visible in the footage (output panel lighting up, prompt starting, a scroll), drop disagreeing anchors, interpolate gaps.
- "Done" isn't "visible": the answer arrived but the phone preview stayed white 3s before painting. Fix: sample the phone region at 5fps, wait for white, then take the first non-white frame plus 0.5s.
- Truncated excerpt misleads the narrator: the script writer only saw the first 3,500 characters, almost causing the voiceover to call a complete JSON blob "cut off." Fix: feed full outputs and forbid claiming truncation unless the text says so.
The author notes fixes 1 and 2 just swap one assumption for another—"footage is ground truth" assumes pixels are right and the clock wrong; the white-then-not-white test assumes the pane starts white. Open questions: where should ground truth live (content anchors, a trusted event log, or drift-proof capture), and how to catch narration-vs-footage mismatches without watching everything?
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