A broadcaster's studios on an IP network: uncompressed video over 100G, locked to a single clock

A television facility is a clock with cameras attached. For decades the work flowed through coaxial SDI cables and a baseband router, which made timing simple and expansion expensive. Each new format, such as UHD, needed more cable and more router ports, and the router itself was a single point of failure on air. The broadcaster wanted IP, but its engineers had one condition: nothing viewers can see may be worse than SDI, whether a dropped frame, a drifting audio sync or a switch that takes a second to settle.

SMPTE ST 2110 is the standard built for that condition. Video, audio and ancillary data travel as separate RTP multicast flows (ST 2110-20, -30 and -40), so a studio can route audio without touching video. An uncompressed 1080p59.94 stream is about 2.5 Gb/s and a UHD stream about 10 Gb/s, so a single 100G QSFP28 port carries around nine UHD flows. The facility therefore uses two independent spine-leaf fabrics, Red and Blue, built from 100G links. Every sender duplicates its streams across both, and every receiver combines them with SMPTE ST 2022-7 seamless protection switching, so a failed link, switch or fiber on one fabric is invisible on air.

Time is what makes it work. A pair of GNSS-disciplined grandmaster clocks distribute IEEE 1588 PTP in the SMPTE ST 2059-2 profile, with boundary clocks in every switch so that timing does not degrade across hops, and hardware timestamping in the network cards. Source-specific multicast (IGMPv3 and PIM-SSM) keeps flows from flooding the fabric, and bandwidth-aware admission refuses a new flow rather than silently oversubscribing a link. Operators never see this: AMWA NMOS IS-04 and IS-05 let the broadcast control system discover devices and connect a camera to a monitor by name.

The cutover was designed to be boring. IP and SDI ran in parallel for several months, with SDI-to-IP gateways carrying existing equipment into the new fabric, and the first live programs moved to IP only after weeks of rehearsal on the fabric with real production traffic. Each studio switched over in the quiet hours between news cycles, with the SDI router kept ready as a fallback until the studio had gone a month without an incident. Remote production uses JPEG XS compression over WAN circuits, so a venue can feed cameras to the central control room with sub-frame delay.

Testing was done against the standards, not by eye. An analyzer checked sender packet timing against the ST 2110-21 timing model, PTP offsets were logged continuously and compared to a second GNSS reference, and every failure case was exercised: pulling a spine link, rebooting a leaf, failing the primary grandmaster, and flooding a port with unrelated multicast. With ST 2022-7 in place, the failure drills produced no lost frames at the receivers; the grandmaster failover produced a clean handover inside the tolerance. The result is a facility in which a new studio is a set of leaf switches and fiber rather than a room of coax, and every device agrees on the time to within a fraction of a microsecond.