Claude Code repairs a hackathon video’s audio sync

A hackathon presenter used Claude Code to combine a webcam pitch with gameplay footage, captions, sound design and music. The first attempts exposed a practical failure: the agent said lip synchronisation was fine even though the presenter could see it was wrong. The author replaced reassurance with measurements on each rendered file.

The verification step decodes the final output, compares sample counts with duration, cross-correlates the voice against the original in eight-second windows and compares MediaPipe mouth movement with voice energy. A large FFmpeg filter graph had produced an AAC track with 114 seconds of timestamps but only 105 seconds of audio samples. Resampling branches to 48 kHz and rendering picture and sound separately fixed that problem.

Cutting by frame number and the corresponding audio-sample number removed drift from repeated timestamp rounding. Splitting transcription at silence boundaries improved late Whisper captions, and alignment with the supplied script corrected jargon. The author also used timestamped Chrome screencast frames and event logs for sharp gameplay footage. After many iterations, Claude packaged the learned scripts and verification procedure as a reusable skill. This is a reported successful repair of one production workflow, not proof that every later video will be synchronised automatically; the presenter supplied the visual checks that revealed the original defect.

Prompt
Suggested prompt (written by Agents In Use, not the author's)

Source: Reddit · u/Codes_with_roh on Reddit