ADR-011: Static film grain by default

• Status: accepted · Date: 2026-10-15

Context

FR-RT-5 asks for grain chosen from pre-generated tiles by frame index. Measured on a 6 s excerpt of examples/season1/ep01 (master settings, CRF 18): no grain 1.9 Mb/s, grain refreshed every frame 64.5 Mb/s, every 6 frames 21.5 Mb/s, static 5.9 Mb/s. Per-frame noise is incompressible: it makes masters ~500 MB, slows every encode, and starves the size-capped share file of bits for the actual content. TikTok/Reels/Shorts re-encode uploads and remove fine grain anyway.

Decision

Grain is a seeded noise texture whose offset is chosen from 8 positions by frame index at the rate theme.chrome.grain_fps. The default is 0 (static texture). Series that want animated grain can set e.g. grain_fps: 6 and accept the bitrate cost.

Consequences

The look keeps its texture, renders stay deterministic, and share files spend their bits on text and diagrams.