- Replace single `ffmpeg -vf fps=1/interval` call (full video decode) with per-frame `ffmpeg -ss <ts> -frames:v 1` calls (keyframe seek) - 6-8x faster on ARM: 180s+ → 33s for 60 frames from 30min video - Per-frame timeout 30s (was 120s single call), failed seeks logged and skipped - Verified end-to-end: 30min 360MB video → 60 candidates → 12 keyframes in 39s