The short answer: SDI is a dedicated video cable — predictable, essentially zero-latency, and indifferent to whatever else is happening in your building. NDI is video over your computer network — dramatically cheaper to expand, endlessly flexible, and only as reliable as the network you run it on. Most working productions today use both: NDI for flexibility and reach, SDI for the paths where guaranteed timing matters most.
On Office Hours Global’s daily live panel — where broadcast engineers, streamers, and systems integrators have answered production questions every single day since March 2020 — the working consensus is that this is no longer an either/or question. It’s a question of which signal belongs on which transport. Here’s how to decide.
What each one actually is
SDI (Serial Digital Interface) carries uncompressed video over coaxial cable with BNC connectors. One cable, one signal, one direction. It has been the backbone of professional broadcast for three decades: 3G-SDI carries 1080p60, and 12G-SDI carries 4K60 on a single cable. Nothing shares the wire, so nothing competes with your picture.
NDI (Network Device Interface), created by NewTek and now developed under Vizrt, sends video over ordinary Ethernet networks. Full-bandwidth NDI compresses lightly (roughly 100–150 Mbps for 1080p60), while NDI|HX uses stronger H.264/H.265 compression to fit cameras and mobile devices onto Wi-Fi or constrained links. Any device on the network can see any NDI source — one cable can carry many signals, in both directions, plus tally, control, and audio.
The comparison that matters
| Factor | SDI | NDI |
|---|---|---|
| Latency | Effectively zero (nanoseconds) | Roughly a frame for full NDI; more for NDI|HX |
| Cost to add a source | A cable run + a router/switcher input (hardware grows expensive) | Often just a network port — switch capacity is cheap by comparison |
| Distance | ~100 m on good 3G coax before re-clocking; fiber for longer runs | Anywhere the network reaches — across the building or, with care, across the world |
| Reliability model | Deterministic: if the cable is good, the signal is good | Shares the network: bandwidth planning and switch configuration are your reliability |
| Signal quality | Uncompressed | Visually excellent, but compressed — a consideration for chroma key and heavy grading |
| Extras on the wire | Video + embedded audio | Video, audio, tally, PTZ control, metadata — bidirectional |
| Timing/genlock | Native, frame-accurate | Handled by receivers; fine for most work, not for hard broadcast sync without care |
When SDI is the right answer
- Latency-critical paths: IMAG screens in a live venue, where even one frame of delay between stage and screen is visible.
- Chroma key and finishing: uncompressed sources key more cleanly.
- Hostile environments: a coax run doesn’t care about a misconfigured switch, a multicast storm, or the guest Wi-Fi.
- Existing broadcast plants: if the router, switcher, and cameras already speak SDI, the marginal cost of staying SDI is low.
When NDI is the right answer
- Growing systems on a budget: adding a tenth source to an NDI network costs a fraction of adding a tenth SDI input.
- Software-centric production: vMix, OBS (via plugin), TriCaster, and most modern tools treat NDI sources as native inputs — no capture cards.
- Distributed productions: sources in other rooms, other buildings, or remote guests’ machines.
- PTZ camera fleets: one Ethernet cable delivers video, power (PoE), and control to each camera.
The panel’s take
Ask this question on the show and you’ll hear the same practical pattern from people who build these systems for churches, campuses, corporate studios, and trucks: run NDI as the fabric, keep SDI for the critical last hops. A typical modern mid-size system uses NDI to move sources around the facility and into software switchers, with SDI reserved for program output to screens, hardware backup paths, and anything that keys. And one warning comes up every time: give NDI its own network, or at least its own VLAN. A gigabit port carries roughly six to eight full-bandwidth NDI streams; the moment your video shares a wire with the office file server, your reliability story belongs to the IT department.
Frequently asked questions
Can I mix NDI and SDI in one system?
Yes — nearly everyone does. Inexpensive bidirectional converters translate between the two, and most software switchers take both natively. Design each signal path around its requirement, not around loyalty to one standard.
Does NDI need 10-gigabit networking?
Not to start. A quality gigabit switch handles a handful of full-NDI streams comfortably. Facilities grow into 10GbE on the trunk lines between switches first, long before individual devices need it.
Is NDI|HX good enough for production?
For camera acquisition, interviews, and remote sources — usually yes. For chroma key or heavy post-processing, prefer full NDI or SDI upstream. HX’s stronger compression is the tradeoff for its tiny bandwidth.
What about SMPTE 2110?
ST 2110 is the uncompressed-over-IP standard used in high-end broadcast plants. It combines IP’s flexibility with SDI-grade quality — at broadcast-plant prices and engineering complexity. For most organizations reading this page, NDI + SDI covers the need.
Still deciding for your specific room? Ask the live panel — real broadcast engineers answer questions like this on the air every single day, free.
This guide reflects discussions from Office Hours Global’s daily live panel — more than 2,000 consecutive shows of production Q&A since March 2020. Office Hours Global is a registered 501(c)(3) nonprofit organization (EIN 87-2070606). We have no affiliate relationships on this page; product mentions are editorial.