NDI, from NewTek, moves broadcast-quality video over a normal network: any source announces itself, any receiver on the LAN can take the feed. A VJ laptop, an OBS stream rig, and a camera can share pictures with nothing but a switch between them.
How it works
NDI is discovery plus compression plus transport. Sources broadcast their presence on the local network, so receivers list them by name with no addressing to configure. The video itself travels lightly compressed, tuned so that a gigabit port carries several HD streams with quality that survives production use. Variants trade differently: full NDI favors quality on wired networks, NDI HX compresses harder for cameras, phones, and Wi-Fi. Audio rides along in the same stream, which quietly solves a whole category of sync problems.
NDI, SDI, and capture cards
Broadcast houses ran SDI coax for decades: one cable, one signal, bulletproof and inflexible. Capture cards bring HDMI into a computer one port at a time. NDI replaces the point-to-point thinking with a bus: everything on the switch is a patchbay, and adding a source costs a network drop rather than a card slot. The price is latency, low but real, roughly a frame or two, fine for streams and IMAG, worth counting in tight reactive chains. Wired gigabit is the floor for serious use; Wi-Fi NDI is for convenience, never for shows.
NDI in visuals rigs
In visuals work NDI is the interchange layer between machines, complementing Syphon (macOS) and Spout (Windows), which do the same job between apps inside one machine. A common rig: generative content rendered on one laptop, sent over NDI to the machine running the media server or stream, with control staying local to each.