CKey Format v0.16.0 — Profile 3 Extended Capacity

Status: experimental byte-codeword and renderer profile. This revision emits format=16 (10), profile=3. It supersedes Format 0.10.0 for new Profile 3 symbols; decoders retain Format 0.10.0 readability. It is not camera validated.

Frame and correction

Profile 3 carries 1–2,048 binary bytes. Its frame is C7 4B 10 03 LLhi LLlo payload CRC32C, zero-padded to 2,230 data bytes. The CRC-32C covers all preceding frame bytes. Data are divided into ten 223-byte blocks, each systematic RS(255,223) over GF(256), primitive polynomial 0x11D, primitive element 2, roots alpha^0...alpha^31. Each block has 32 parity bytes and corrects up to 16 unknown byte errors. Output byte 10*i+b is byte i from block b, distributing local loss across blocks.

Canonical finder geometry

The field is 116 by 116 units. Its outer boundary is the continuous rounded square from (2,2) to (114,114), radius 14, width 2.6. Each finder is one broad, round-capped arc inside that border. The top-left local finder is centred at (16,16), radius 9.20, width 3.20, with its exterior-quadrant path from (6.80,16) to (16,6.80). The concave/open mouth faces down-right, toward the polar field. Reflection creates the other three corners; only top-left is split at its diagonal with a cap-compensated 3.8-unit visible gap. Finder reservations cover only their strokes plus guard band, never an arbitrary square outside a corner.

Capacity geometry

The Cartesian matrix is 232 by 232 at 0.5-unit pitch, with 0.34-unit modules. The polar matrix has 24 rings, 288 slots per ring, radii 9.50 + 0.65*r, and uniform dot radius 0.075. A run of two or more occupied slots is a connected, round-capped arc; its angular span is exactly its occupied slot count, so a four-slot arc equals four dots' slot span and stroke width.

The ray matrix has 576 bearings beginning at radius 26.30. Aside from three reserved Ray Key bearings, every ray encodes three bits using four Gray-coded lengths (0.80, 1.65, 2.50, 3.35) and calibrated 0.16/0.28-unit weights. The Grid Key uses ordinary payload geometry to establish pitch and clear space; fixed-size or fixed-distance decoder ladders are non-conformant.

The core validates Profile 3 codewords and renders its exact geometry, but the mobile/image decoder does not sample this profile. It must not be advertised as scannable until projective sampling and physical-capture testing pass.