When to use

• You need to decide a sampling stride/FPS and ensure all downstream outputs (interval instructions, per-frame artifacts, etc.) cover the same frame range with consistent indices.

Core steps

• Read video metadata: frame count, fps, resolution.
• Choose a sampling strategy (e.g., every 10 frames or target ~10–15 fps) to produce sample_ids.
• Only produce instructions and masks for sample_ids; the max index must be < total_frames.
• Use a strict interval key format such as "{start}->{end}" (integers only). Decide (and document) whether end is inclusive or exclusive, and be consistent.