SDI (Serial Digital Interface) vs SMPTE ST 2110

Q: SDI (Serial Digital Interface) vs SMPTE ST 2110: Do I still need SDI if the facility is going IP?

SDI (Serial Digital Interface): SMPTE's uncompressed baseband digital video interface, carried on 75 ohm coax and BNC from 270 Mb/s standard definition up to 11.88 Gb/s 12G. It is still the backbone of most live video: point to point, no negotiation, no network, and it either locks or it does not. SMPTE ST 2110: A suite of SMPTE standards for carrying uncompressed video, audio and ancillary data as separate RTP streams over a managed IP network, all locked to PTP. It is the broadcast plant replacement for an SDI router, used in OB trucks, studios and large arena control rooms.

showstack / compare / sdi-vs-smpte-st-2110

Do I still need SDI if the facility is going IP? Below is every field we hold on both, side by side. Each one is sourced on the individual entry, and anything nobody could source is left blank rather than guessed.

Side by side

	SDI (Serial Digital Interface)	SMPTE ST 2110
Category	video-transport	video-transport
Flow	Media — large, continuous, on time and in order	Media — large, continuous, on time and in order
Transport	other, fibre	udp
Multicast		yes
Spec availability	open-published	published-paid
Steward	SMPTE (Society of Motion Picture and Television Engineers)	SMPTE (Society of Motion Picture and Television Engineers)
First published	—	2017
Status	current	current
Our confidence	verified	reported

Both are media flows. Anything that starves the link — usually a management transfer nobody scheduled — and jitter that outruns the receive buffer. That applies equally to either, so it is not a discriminator here.

What each one carries

Capability defined by the specification, not by any one product. A blank means the specification does not fix it, which is itself the answer on a transport like SRT.

	SDI (Serial Digital Interface)	SMPTE ST 2110
Sample rates	48 kHz	48 kHz
Audio bit depth	24-bit	16-bit, 24-bit
Audio channels	up to 16	—
Audio encoding	Embedded AES3 in the ancillary data space	ST 2110-30, which is AES67
Resolution	3840x2160	Not fixed by the specification
Frame rate	up to 60 Hz	Not fixed by the specification
Colour sampling	4:2:2, 4:4:4	4:2:2, 4:4:4
Video bit depth	10-bit, 12-bit	8-bit, 10-bit, 12-bit, 16-bit
Video compression	None — uncompressed	None — uncompressed essence

SDI (Serial Digital Interface), audio: Sixteen channels in four groups, riding in the horizontal blanking.

SDI (Serial Digital Interface), video: 3840x2160 needs 12G-SDI on a single link; above that you are on two or four. The rate tiers are SD 270 Mbit/s, HD 1.485, 3G 2.97, 6G 5.94 and 12G 11.88. Cable reach falls as the rate rises, because coax loss goes with the square root of frequency and the frequency that matters is half the bit rate.

SMPTE ST 2110, audio: Essence streams are separate, so audio and video are independently routable — which is the whole point of 2110 and the reason lip sync becomes something you have to manage rather than something you get.

SMPTE ST 2110, video: ST 2110-20 is resolution and frame-rate agnostic by design; what limits you is the link. Uncompressed HD is around 1.5 Gbit/s and UHD around 12 Gbit/s, so the practical ceiling is the network rather than the standard. Audio travels separately in ST 2110-30 as AES67.

Speaks both (1)

These are the safe choices if you have not committed to either, or need to bridge the two.

Brompton Tessera SX40 Brompton Technology

SDI (Serial Digital Interface) only (7)

Millumin Anomes (Philippe Chaurand)
Ventuz Ventuz Technology
Analog Way Aquilon RS4 Analog Way
Barco Event Master E2 Barco
Blackmagic ATEM 4 M/E Constellation HD Blackmagic Design
Blackmagic Smart Videohub 40x40 Blackmagic Design
NovaStar MX40 Pro NovaStar

SMPTE ST 2110 only (6)

Smode Smode Tech
vMix StudioCoast
Analog Way Alta 4K Analog Way
Brompton Tessera S8 Brompton Technology
Megapixel HELIOS LED Processing Platform Megapixel VR
Modulo Kinetic Modulo Pi

What goes wrong with SDI (Serial Digital Interface)

The bit rate is fixed by the standard, not by the picture. ST 259 is 143/270/360 Mb/s, ST 292-1 is 1.485 Gb/s (or 1.485/1.001), ST 2082-1 is 11.88 Gb/s. A "12G" run is really an 11.88 Gb/s run.

The connector is 75 ohm BNC per IEC 61169-8. 50 ohm BNCs are mechanically identical, will fit, will pass SD happily, and will then fail at 3G and 12G in a way that looks like a bad cable everywhere else in the chain.

Cable loss is specified at half the clock frequency, around 20 dB for ST 292-1. The same drum of cable that carries HD across a stadium will not carry 12G, so re-derate every existing run when you upgrade rate.

There is no negotiation, no handshake and no error correction. A marginal link produces sparkles or black frames, and the receiver reports lock rather than quality, so "it says it is locked" proves very little.

Audio, timecode and captions ride as ancillary data in the blanking intervals. Some converters, re-clockers and scalers pass video cleanly and drop ANC, so timecode and captions vanish with no error anywhere.

Return loss is specified at 15 dB and rise time at 270 ps for HD, 45 ps for 12G. Cheap patch panels and barrel connectors are the usual reason a 12G path that works on the bench fails in the rack.

What goes wrong with SMPTE ST 2110

Video, audio and ancillary data are separate streams with separate multicast addresses. Losing one leaves the others running, so "no audio" or "no timecode" can present as a perfectly healthy video path.

Everything hangs off PTP. ST 2110-10 defines the system timing model, so a grandmaster that steps, or two grandmasters fighting, takes the whole plant out at once rather than degrading gracefully.

ST 2110-20 video is genuinely uncompressed. Bandwidth is set by raster and frame rate, not by an average bitrate, so plan link capacity from the video format and leave headroom before you commit to a switch.

ST 2110-21 defines sender traffic shaping types. A sender and a receiver with mismatched shaping expectations gives intermittent picture breakup under load, not a clean failure you can point at.

ST 2110-30 audio is closely related to AES67 but the two do not automatically interoperate. Packet time and channel count profiles have to match on both ends before anything passes.

The suite is a dozen separate documents (ST 2110-10, -20, -21, -22, -30, -31, -40, -41, -43, plus RPs) and they are priced individually. Budget for the whole set, not one part number.

Sources

SMPTE ST 292-1:2018 — 1.5 Gb/s Signal/Data Serial Interface — SMPTE primary
SMPTE ST 259:2008 — SDTV Digital Signal/Data, Serial Digital Interface — SMPTE primary
SMPTE ST 2082-1:2023 — 12 Gb/s Signal/Data Serial Interface — SMPTE primary
SMPTE EG 2111-1:2021 — SD-SDI and HD-SDI Standards Roadmap — SMPTE primary
ST 2110 Suite of Standards — SMPTE primary
SMPTE ST 2110 FAQ — SMPTE primary
SMPTE Publishes ST 2110 Standards for Professional Media Over Managed IP Networks — TV Tech

Disagree with any of this?

Every claim above comes from one of the two entries and carries a source. If one is wrong, correcting it is a single file and it fixes this page automatically. Edit SDI (Serial Digital Interface) or edit SMPTE ST 2110.