NDI bridge

Browsers cannot join an NDI network: there is no mDNS discovery and no raw TCP or UDP in a web page, and the NDI SDK is closed source. WebToe therefore splits the job in two. A small local bridge owns the NDI side using your own NDI runtime, and the ndi in / ndi out TOPs do the pixel work in the browser, talking to the bridge over a WebSocket on localhost.

NDI network ⇄ packages/ndi-bridge (Node; ws, optional grandiose)
            ⇄ ws://127.0.0.1:9980   JSON control + binary frames
            ⇄ ndi in / ndi out TOPs ⇄ video kernels (WASM, JS fallback) ⇄ GPU textures

#Try it without NDI

From a checkout of the repository (after npm install):

node packages/ndi-bridge/index.mjs --mock

Mock mode needs nothing from NDI: the bridge generates an animated UYVY test pattern as a source called WebToe Mock (Pattern) and accepts frames sent from the browser. In the editor, add an ndi in TOP: it connects to ws://127.0.0.1:9980 and shows the pattern. Add an ndi out TOP after any image and the bridge logs the frames it receives.

#Real NDI

1. Install the NDI runtime from Vizrt.
2. Install the optional binding in the bridge package: npm i grandiose inside packages/ndi-bridge.
3. Run node packages/ndi-bridge/index.mjs (no --mock). Without grandiose it falls back to mock behaviour and says so.

Bridge options: --port <n> (default 9980), --mock, --mock-name <name>.

#The protocol

Version 1, kept in sync between packages/ndi-bridge/index.mjs and packages/ops/src/video/protocol.ts:

• Control messages are JSON text: hello (version and mode), sources (list of names), subscribe { source }, send-open { name, w, h, fps }.
• Frames are binary: a 24-byte header (magic WTNF, u32 width, u32 height, a fourcc RGBA or UYVY, an f64 timestamp) followed by the pixels.

#Why WebAssembly here

Converting UYVY to RGBA (BT.601) and swizzling BGRA, every pixel of every frame, is the one place in the engine where a WASM kernel pays for itself. The kernel is written in AssemblyScript (packages/wasm-kernels), compiled to a 1 KB .wasm that the app loads at startup; the JavaScript implementation is the permanent fallback and the unit-tested reference. The console says which one is running (video kernels: wasm).

#Limits

ndi out reads pixels back synchronously on WebGL2 (throttled by its send rate); an asynchronous readback for WebGPU and compressed transport are listed follow-ups. Source discovery is by name in the ndi source parameter.

NDI® is a trademark of Vizrt NDI AB. WebToe ships no part of the NDI SDK; real mode uses the runtime you install.