SMPTE ST 2110
SMPTE ST 2110 Rationale
ST 2110, a suite of standards from the Society of Motion Picture and Television Engineers (SMPTE), defines the real-time transport of professional video, audio, and ancillary data over IP networks. It is particularly important in the support of live video production environments that require both high bandwidth and ultra-low latency.
Like SMPTE ST 2022-6, it aims to replace the SDI industry suite of standards in broadcast production and distribution infrastructure. However, SMPTE ST 2110 advances beyond the simple packetization of the entire SDI signal by separating the video, audio, and data streams (essences) for better efficiency and flexibility.
Why SMPTE ST 2110
The adoption of SMPTE ST 2110 offers several key advantages:
- Flexible and Scalable Transport (Moving Beyond the Single Cable Stream): Unlike SDI, a technology where a single cable carries a fixed, multiplexed stream of video, audio, and ancillary data, ST 2110 utilizes IP networking to separate these components. This allows for nearly infinite scalability and flexibility. A single network connection can handle multiple streams, and the capacity can be easily increased by upgrading network infrastructure without ripping and replacing signal cables.
- Decoupled Content Streams for Enhanced Workflow Flexibility: ST 2110 defines separate IP streams (known as “essences”) for each content type; This separation is a paradigm shift. It eliminates the need for demuxing and remuxing processes traditionally required to extract or insert content. For example, an audio engineer can subscribe only to the audio streams, process them, and send new audio streams back to the network, all without touching the video.
- Leveraging Established and Reliable IP Architectures: ST 2110 is built upon widely adopted IP protocols, allowing media facilities to benefit from decades of development in the IT domain. This includes utilizing standard, off-the-shelf Ethernet switches and routers, simplifying infrastructure management, reducing proprietary hardware costs, and enabling the use of common network security and monitoring tools.
- Simplified and Dynamic Software-Based Routing: In an SDI based facility, changing the path of a signal requires physically patching cables or relying on a dedicated, hardware-based router. In contrast, ST 2110 uses IP addressing for routing. This enables easier, faster, and more dynamic modifications to the contribution and distribution topology between sources and receivers, often managed through a centralized controller (NMOS/IS-04 and IS-05 standards govern discovery and connection management). This agility is crucial for live production environments.
- Seamless Audio Compatibility with AES67: The audio transport specification within ST 2110 is based on the AES67 standard. This intentional alignment ensures interoperability with the vast, existing installed base of professional audio-over-IP equipment, including Dante and Ravenna devices. This allows broadcasters to integrate their existing audio ecosystem directly into the new ST 2110 video infrastructure with minimal friction.
- Infrastructure Sharing and Interoperability with Other IP Standards: By standardizing on a common IP infrastructure, ST 2110 environments can easily coexist and share network resources with other video transport technologies. This includes compressed video standards like SRT (Secure Reliable Transport), NDI (Network Device Interface), and DASH (Dynamic Adaptive Streaming over HTTP). This shared infrastructure eases the interoperability between uncompressed (ST 2110) worlds, typically used for live production, and compressed workflows used for contribution, distribution, and OTT delivery, creating a unified and efficient media network ecosystem.
Key Components
The SMPTE ST 2110 suite comprises a collection of essential normative documents categorized into distinct domains: System, Video, Audio, and Metadata. The most notable parts are summarized below:
| ST 2110-10 — System Timing and Definitions |
This foundational standard establishes the principle of separating video, audio, and data essences. It uses RTP for transport and SDP for announcement. Crucially, it defines the synchronization of all essences using a common clock based on the PTP protocol, following the SMPTE ST 2059-1 and ST 2059-2 standards.
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| ST 2110-20 — Uncompressed Active Video |
This part details the specific RTP and SDP formatting and parameterization required for the transport and announcement of uncompressed video essences.
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| ST 2110-21 — Traffic Shaping and Delivery Timing for Video |
Complementing ST 2110-20 and ST 2110-22, this document specifies the various packet delivery timing models that senders must implement. It introduces distinct classes of models for senders (Narrow, Narrow Linear, and Wide) and receivers (Narrow, Wide, and Asynchronous).
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| ST 2110-22 — Constant Bit-Rate Compressed Video | This extends the ST 2110 family to support compressed video without mandating a specific codec. Interoperable format and packaging relies on external initiatives, such as the VST TR-08 for carrying JPEG-XS within the ST 2110-22 transport.
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| ST 2110-30 — PCM Digital Audio | Beyond RTP parameterization, this standard imposes SDP constraints on audio essences to ensure compliance with the AES67 standard. To simplify interoperability checks between senders and receivers, it defines multiple conformance levels based on different sampling rates, packet times, and channel densities.
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| ST 2110-40 — Ancillary Data | Based on IETF RFC 8331, this part specifies how metadata, originally carried in Ancillary Data packets (as defined by SMPTE ST 259-1), is encapsulated into dedicated RTP streams and precisely synchronized with the corresponding video and audio essences.
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| ST 2110-41 — Fast Metadata Framework | Offers a more flexible approach than ST 2110-40, going beyond simple ANC data transposition. It supports arbitrary metadata, which can be finely synchronized with audio/video essences (e.g., for ad insertion) or transmitted independently.
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| ST 2110-43 — TTML for Caption and Subtitles | This part elevates closed caption metadata from its legacy ANC transport to a standalone essence. It is based on the W3C recommendation, Timed Text Markup Language 2 (TTML2).
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2110 Video QoS & QoE Monitoring Solution
Synchronizing with PTP
SMPTE ST 2110 differs from ST 2022-6 in its approach to signal packaging: instead of encapsulating the complete, synchronized SDI signal (video, audio, and data), ST 2110 separates these components into individual essences. This separation “by design” requires a robust synchronization mechanism to ensure that at the destination (such as a mixer, processor, or monitor), these separated flows are correctly recombined. Maintaining this synchronization is critical to avoid drift, prevent lip-sync errors, and facilitate clean switching. Furthermore, it ensures interoperability by providing a common timing implementation for equipment sourced from multiple vendors.
To implement this precise synchronization, ST 2110 specifies the use of the IEEE 1588 Precision Time Protocol (PTP). PTP achieves sub-microsecond clock synchronization across network devices via message exchanges, typically packetized over UDP/IP. In this system, each networked device synchronizes its clock to a single, highly stable source known as the Grandmaster Clock (GM). The GM, in turn, is usually slaved to a high-accuracy external reference, such as a GPS signal or an atomic clock.
This common clock reference allows all senders to coherently timestamp the RTP packets for their respective video, audio, and data essences. Consequently, receivers can de-jitter the incoming packets, and ensure that frames and samples are reconstructed and presented with highly precise timing.
Orchestration: The Role of NMOS in SMPTE ST 2110 Environments
As we presented above, the ST 2110 suite of standards fundamentally changes signal management by introducing flexibility through essence-based transport over standard IP networks (RTP over IP). This approach allows for software-based routing, decoupling of hardware and function, and highly efficient resource utilization.
That said, this flexible infrastructure requires an equally sophisticated control system to manage the complexity of thousands of individual IP flows, senders, and receivers. This is where NMOS (Networked Media Open Specifications) becomes essential.
While ST 2110 defines how the media is transported, NMOS, a family of specifications promoted by the Advanced Media Workflow Association (AMWA), defines the necessary standards and protocols for managing the devices and connections: how to discover, register, manage and connect devices carrying that media.
NMOS is fundamentally a family of REST-like HTTP APIs, defining a global data model for key entities that equipment must implement (primarily Nodes, Devices, Senders, Flows, and Receivers).
The foundation for seamless orchestration of ST 2110 equipment lies in two essential specifications:
- IS-04 (Discovery and Registration): Addresses how devices are found and registered within networks. It defines three API subsets:
- Registration API: Allows a Node to register its resources.
- Query API: Facilitates querying of all registered resources.
- Node API: Enables peer-to-peer discovery by finding resources on a specific Node.
- IS-05 (Connection Management): Manages the establishment and control of media connections. The specified API provides the mechanism to change settings on Senders and Receivers, thereby how to connect and route sources to their destinations.
However, NMOS extends well beyond these two core building blocks, addressing a wide range of other concerns such as audio channel mapping, systems parameterization, devices configuration, or events notification.
In summary, ST 2110 provides the technical foundation for flexible IP media transport, but it is NMOS that delivers the critical control plane. Together, each technology makes large-scale 2110 deployments manageable, interoperable, and capable of fully realizing the benefits of software-based routing.