bayerlink

Raw sensor data over an HDMI/DVI link.

FPGA boards rarely have camera connectors; nearly everything has HDMI. The bayerlink protocol treats a display link's active area as a byte container: packed raw Bayer samples, one camera line per display line, self-described by a 48-byte header (magic, version, V4L2 fourcc, geometry, frame counter, stripe and source identity for multi-link use, CRC). Real sensor data into any board with HDMI-in — no MIPI hardware, no deserialisers, no per-sensor bring-up on the receiver.

New here? GUIDE.md routes by what is on your desk — a Pi, an FPGA board, a $10 capture stick, a sensor that is not 12-bit.

PROTOCOL.md is the specification. This package is its reference implementation, and vectors/ pins the exact bytes, so a conforming implementation in any language never has to run this one.

Independent implementations are unrestricted and encouraged; say "speaks bayerlink v2" and you are conforming, not licensing. See TRADEMARK.md for the one thing the name asks of you.

The package

import bayerlink

frame = bayerlink.encode_frame(raw, "RGGB", frame_seq=7)   # (H, W, 3) uint8 out
header, raw = bayerlink.decode_frame(captured)              # and back
header.bayer_order, header.width, header.frame_seq

It runs on both ends: encoders build containers with it, and a receiver's host software decodes captured frames with the same module — one implementation to disagree with the spec, which is the fewest possible.

bayerlink.pattern carries the link-proving test patterns (counting, gradient, checker, corners) every encoder and receiver bring-up uses; checker and corners pin 0 and full scale, the first casualties of a limited-range link.

Implementations

The registry lives at the end of PROTOCOL.md. Reference encoder: picam2hdmi (Raspberry Pi, every libcamera sensor). To be listed: implement the spec, pass the vectors, open an issue.

Funding

Developed independently; recurring support via github.com/sponsors/lanserge, or write first: s.rabykin@gmail.com. Sponsorable capability targets carry the sponsorable label on the issue tracker — currently the PiSP compressed payload family and the laptop replay player. Scope is agreed in writing before work starts; sponsored work lands in the open tree immediately, licensed like everything else — sponsorship buys ordering and named credit, not exclusivity. The person behind it: serge.rabyking.com.

Licence

Apache-2.0 — chosen over MIT for two of its clauses, not for anything this project owns. Section 3 means every contributor grants implementers a licence to any patent claims their contribution would infringe: no such patents are known or claimed, and the clause is insurance FOR implementers, not an assertion by this project. Section 6 makes explicit that the licence covers the text and code, never the name (see TRADEMARK.md). A protocol meant for many independent implementers benefits from both being written down.