LlamaCasty/TASKS/task-53-output-formats.md

TASK 53 — Output-format verification: Shorts / TikTok geometry (queued 2026-10-08)

Catalog: TASKS.md — status and requirements live here.

Why: the output formats have never been tested end-to-end. The site claims "vertical 1080p60 (9:16)" and Shorts-style streams, but nobody has verified that the geometry actually comes out correct for Shorts and TikTok — safe zones, caption clearance, and the text-safe inset all still need checking against a real capture.

Goal: prove the vertical/short-form path is geometrically correct, or fix the gaps and then prove it. Make the output formats a tested, locked contract instead of an assumption.

Slices (one integration test each, in order):

1. ☐ What we actually emit — enumerate the real encoding configurations (widescreen 1080p60/ 1080p30/720p60/720p30 + vertical 9:16 1080p60) and pin them in one place (FfmpegArgs-adjacent), each with its own geometry contract test. This turns "formats exist" into "formats are defined".
2. ☐ 9:16 geometry — vertical render must be true 1080×1920 (or the GUP-negotiated size) with the composite laid out for a phone: viewer-safe top strip (TikTok/Shorts overlays live top-left and bottom), caption/text clearance, and the webcam not cropped off-centre. Test: composite a known layout, decode the output frame, assert dimensions + element placement vs the contract.
3. ☐ Live-shorts check on a real stream — private Test Stream at 9:16, then pull the thumbnail/ player quirk list from YouTube (Title visible, overlays); confirm nothing the streamer put on screen sits under YouTube's own chrome. This is the "never tested" item the creator flagged — test on a real vertical test stream and cite the observation.
4. ☐ Recorded .mp4 matches output — the saved vertical .mp4 must carry the same 9:16 frame the stream showed, not a squeezed/wider master. Test: record vertical, decode first frames, assert.

Design decisions:

• Geometry is a contract with tests, not a hope. Derived ratios (stream vs composite vs canvas) get a derived-value test so one change can't silently wreck Shorts/TikTok output.
• Keep widescreen untouched — only add what vertical needs (the existing test suite stays green for 16:9).