Broadcast Engineering & IT

SMPTE ST 2110 & NDI: Broadcast Video Over IP Networks

By Infinite Creation · 13 min read

Television broadcast infrastructure is abandoning heavy copper coaxial SDI matrix switchers in favor of high-capacity Ethernet fabrics. This guide covers the engineering principles of video over IP: the SMPTE ST 2110 suite, Precision Time Protocol synchronization, NMOS routing, and NDI versus NDI|HX.

A 1960s mid-century comic book style editorial illustration depicting television broadcast engineers and network architects operating an IP broadcast routing master control room.

1. The Shift from SDI Copper Matrix to IP Fabrics

For decades, television broadcast facilities routed video using Serial Digital Interface (12G-SDI, 3G-SDI) copper BNC cables connected to massive hardware matrix switchers. In traditional SDI routing, video, embedded audio channels, timecode, and closed caption data are bundled into a single monolithic bitstream. If an audio mixer needs to process Channel 7 from a camera feed, an SDI de-embedder must extract the entire stream, process the audio, and re-embed it downstream.

Modern live broadcast facilities use Internet Protocol (IP) networks. In an IP routing architecture, video, multi-channel audio, and metadata travel as independent, unbundled multicast UDP network streams over commercial off-the-shelf (COTS) 25GbE, 100GbE, and 400GbE network switches. Any workstation, switcher, or audio console can subscribe to any individual essence stream without de-embedding.

2. The SMPTE ST 2110 Professional Suite

The Society of Motion Picture and Television Engineers (SMPTE) created the ST 2110 standard suite to govern uncompressed professional media carriage over IP networks:

ST 2110-10 (System Timing & Synchronization): Establishes global time synchronization across every networked device using IEEE 1588-2008 Precision Time Protocol (PTP v2). PTP synchronizes network packet clocks to within nanoseconds, replacing analog blackburst and tri-level sync cables.
ST 2110-20 (Uncompressed Active Video): Carries only the active visible video pixels (RFC 4175 RTP payload). It strips away legacy analog blanking intervals, reducing raw network bandwidth by up to 20% (e.g. 1080p60 consumes ~2.5 Gbps, 4K UHD 2160p60 consumes ~12 Gbps).
ST 2110-21 (Traffic Shaping and Delivery Timing): Dictates how network senders meter and space packet bursts (Narrow Senders vs Wide Senders) to prevent buffer overflows inside network switches.
ST 2110-30 (PCM Digital Audio): Transmits uncompressed 24-bit PCM audio based on the AES67 standard in 1ms or 125µs packetization times.
ST 2110-40 (Ancillary Data): Transmits subtitles, CEA-708 closed captions, active format description (AFD), and timecode as discrete RTP streams.

3. NMOS: Discovery, Registration & Connection Management

SMPTE ST 2110 defines how data packets travel, but it does not specify how devices find each other or route streams. The Advanced Media Workflow Association (AMWA) created NMOS (Networked Media Open Specifications) to handle control:

NMOS IS-04 (Discovery & Registration)

When an IP camera or multiviewer connects to the network, IS-04 automatically publishes its identity, IP address, and available media flows to a central Registry without manual configuration.

NMOS IS-05 (Connection Management)

Provides REST APIs that broadcast controllers use to instruct a receiver (such as a vision mixer input) to subscribe to a specific multicast stream from an IS-04 sender seamlessly.

4. NDI (Network Device Interface) vs. SMPTE ST 2110

While ST 2110 is the gold standard for multi-million dollar television networks, smaller live studios, corporate video facilities, and churches deploy NDI (Network Device Interface) developed by NewTek / Vizrt:

High-Bandwidth NDI (Full NDI): Uses intra-frame DCT compression (~150 Mbps for 1080p60, ~300 Mbps for 4K). Offers broadcast-grade visual quality with ultra-low latency (under 16 milliseconds) that easily runs on standard 1GbE / 10GbE office switches without complex PTP grandmaster clocks.
NDI|HX (High Efficiency): Uses inter-frame H.264 or HEVC/H.265 compression (10 to 30 Mbps). Ideal for PTZ (Pan-Tilt-Zoom) robotic cameras, wireless mobile video feeds, and low-bandwidth remote broadcast backhaul over public internet connections.

5. Dante & AES67 Audio-over-IP Interoperability

Audio routing in live IP broadcast centers is dominated by Audinate Dante and open-standard AES67. Dante provides zero-configuration discovery and routing through Dante Controller software.

In modern broadcast plants, Dante devices are placed into AES67 Interoperability Mode to communicate natively with SMPTE ST 2110-30 audio streams, allowing mixing consoles, wireless microphone receivers, and intercom panels to route thousands of discrete audio channels across a single fiber pair.

Working Vocabulary

Key broadcast engineering and video-over-IP terms introduced in this guide:

SMPTE ST 2110. The open standard suite specifying the real-time transmission of uncompressed video, audio, and metadata streams over IP networks.
Precision Time Protocol (PTP IEEE 1588). A network clock synchronization protocol providing sub-microsecond timing accuracy across all IP broadcast nodes.
NMOS (Networked Media Open Specifications). An open software control layer (IS-04 discovery, IS-05 routing) used to automate device management in ST 2110 facilities.
NDI (Network Device Interface). A compressed video-over-IP protocol designed for live media production over standard Gigabit Ethernet networks.
AES67. An open interoperability standard for high-fidelity, low-latency audio transmission over IP networks.
Multicast UDP. A network transmission method where a single sender transmits media packets to multiple subscribed receivers simultaneously without duplicating server bandwidth.