Viz Frame Audit

Use after a render or re-render to verify the four defect categories. Skip it when only the deterministic layout --static-check is needed.

The four categories

Videos are inspected against the four standing defect categories below. The catalogue of verified incidents per category lives in references/defect-catalogue.md.

#	Category	Definition	Detection signal
1	Naive arrow	Head too small, head colour mismatch with body, label crossing the dashed line	head_size ≤ 0.24, head_color ≠ body color with near-vertical arrow + label at UP * 0.25
2	Padding intrusion	Text or box within 0.1 of another box edge, or crossing the canvas edge	Box height < content height, row labels at LEFT * 6.0+, 7+ outline lines in a small box
3	Glyph kerning drift	Helvetica Neue + Pango misreads specific glyph pairs ("GE ODE", "g eneration", "fit ness", "cr itic")	Spurious space inside a word, more pronounced at smaller font_size
4	Frame-order error	Empty / half-empty transition frame, content not accumulating, line endpoint missing the last dot	_clear_section + _set_section_title called separately, LaggedStart then separate Create(connectors)

Workflow

1. Decide timestamps — cover the changed sections and adjacent transitions; use existing key-frame manifests when applicable. Stable layout frames and transition frames answer different questions.
2. Extract — ffmpeg -ss <t> -frames:v 1 -update 1 -q:v 2 per timestamp.
3. Inspect — Use the available image-viewing tool so the model sees the actual frame; Bash(cat / tail) will NOT show the image.
4. Classify — for every finding, assign one of the four category numbers.
5. Report — present findings with timestamps and visible evidence. A review request does not authorize edits; if fixes were requested, implement clear defects and ask only about choices that materially change the intended design.
6. When fixes are in scope, re-render and inspect the same timestamps. Compare before/after; check for collateral regressions in adjacent bits.

Workflow details in rules/audit-workflow.md and rules/reporting.md.

File map

File	Purpose
rules/audit-workflow.md	ffmpeg extraction + Read inspection + timestamp selection + iteration loop
rules/reporting.md	The reporting format to the user (Bit / category / location), tone rules, before/after table format
rules/pixel-ratchet.md	Existing pixelmatch-py frame comparison and evidence limits
rules/typography-drift-gate.md	uharfbuzz typography gate reference; verify current code before using historical snippets
references/defect-catalogue.md	12+ verified incidents (filewalk × 5, hero × 7) — location, symptom, fix
references/external-oss.md	Yusuke710/manim-skill (4-phase loop), pytest-mpl (baseline UX), pixelmatch-py, uharfbuzz, frames-mcp — stars / last-push verified 2026-05-21

Quick reference — extract + inspect

Use the isolated extraction example in audit workflow, then inspect each PNG with the available image viewer. Preserve prior renders and audit frames. KO is audited separately because Korean text width differs from English — typographic and padding defects do not transfer 1:1.

Standing line of defence

The verify_hero_layout.py ratchet (covered in [[manim-scene-craft]]'s rules/layout-ratchet.md) catches text-vs-container geometry overflow at compile time. This skill's job is everything the geometric ratchet cannot see: arrow / label spatial relationships, typography drift inside the box, and animation timing. Steps 2 and 3 (uharfbuzz, pixelmatch) extend the compile-time ratchet so the model spends less time inspecting frames manually — see rules/typography-drift-gate.md and rules/pixel-ratchet.md.