Case Study: Implementing SMPTE ST 2110 for a New IP-Based Local TV Station

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In the June issue of the SMPTE Motion Imaging Journal, Jim Beahn and Nikhilesh Kumar present “A Report from a SMPTE ST 2110 Early Adopter: WTTG/WDCA Fox Television Builds an IP-Based Local Television Station.” WTTG and WDCA serve the Washington DC area and are among the 28 stations owned and operated by Fox. The goal of the project was to relocate the stations to an all-new facility in suburban Bethesda, Maryland by late 2021, and to implement an IP-based SMPTE ST 2110 operation built from the ground up. Jim Beahn, VP of engineering and operations for the two stations, led the Fox team, partnering with New Jersey-based integrator Diversified, led by broadcast engineering solutions architect Nik Kumar.

Planning began in early 2019 in conjunction with the NAB show, where a Fox group scheduled meetings with equipment manufacturers, systems designers, and technology experts. After determining the viability of the relatively new ST 2110 technology for media over IP rather than perpetuating conventional serial digital interface (SDI) technology, they issued the green light for a completely ST 2110-based broadcast television plant rather than a piecemeal, hybrid SDI/IP approach. This allowed the completely integrated facility to be fully tested and qualified before a flash cut from the existing plant occurred.

The All-New Facility

The design of the facility called for all signal routing between ST 2110 devices to be performed by network switches, as well as a strong preference for utilizing ST 2110 interfaces. In cases where some equipment was not yet available with native ST 2110 IP-based input/output, they specified SDI-to-IP and IP-to-SDI converters. This allowed immediate encapsulation for distribution as ST 2110 Realtime Transport Protocol (RTP) streams and de-encapsulation for devices with SDI inputs. Additionally, they incorporated the SMPTE ST 2022-7 standard to create two identical, redundant “red” and “blue” RTP media networks, while a third “purple” network supported audio components. The designers believe the new WTTG/WDCA plant to be the first local television origination facility built from the ground up on ST 2110 technology.

SDI versus ST 2110 Facility Designs

SDI-based facilities use coax cables and serial digital signals, while IP-based infrastructure uses fiber and IP signals. There are also major differences in signal flow, monitoring, and troubleshooting techniques. An SDI signal path is typically cabled just as it appears in the schematic drawing, with the output of each device feeding the input of the next, and the use of matrix routing switchers, patch bays and daisy-chained connections. In an ST 2110 facility, all devices are physically cabled directly to a network router and broadcast controller that determine the signal routing and endpoint. Addition and removal of devices from the signal flow do not require any form conventional patching or switching, and monitoring and troubleshooting use the same tools that would be associated with any IP-based network.

System Router

Routing functions for an ST 2110 system are typically performed using a commercially available off-the-shelf IP network router, or in the case of the WTTG/WDCA project, a special-order router carefully selected to carry an ST 2110 payload at data rates that can support future 4K resolution. Their system has approximately 500 physical endpoints supporting some 700 redundant video flows, 800 redundant audio flows, and 300 redundant ancillary data flows. At the core of the network topology, two spine routers (“red” and “blue”) support the redundant streams, while leaf switches are used as aggregation switches for low-bandwidth audio traffic.

Broadcast Control System

The Broadcast Control System manages and controls routing between sources and endpoints, receiving commands from a router control panel or automation system to trigger switches. It subsequently communicates with the intended receiver, triggering it to issue a “join” command to the sender with which it needs to connect. Once the multicast subscription is established, the network forwards the multicast traffic from the sender to the receiver via networking routing protocols.

Production Control Room Equipment and Studio Cameras

Selection of video production equipment was limited by the ST 2110-based device availability and influenced by the desire to use the same production automation and graphics systems used by other Fox stations. As project criteria specified a minimum of 60 inputs, the production switcher required a great deal of internal bandwidth, as well as firmware upgrades providing an increased buffer size to smooth out occasional large data bursts. Firmware upgrades were also required for the studio cameras to achieve standards compliance and compatibility.

Master Control Equipment

When the design of the new facility was being finalized, very few ST 2110-qualified master control switchers were available from manufacturers. The team therefore eliminated a physical switcher in this area of the design, substituting virtual switching with keying of graphics and video effects accomplished with a dedicated graphics processor. A major challenge was that Fox-owned and operated stations were standardized with master control ingest/playout systems available only with SDI I/O rather than the necessary ST 2110 I/O. In addition, closed captioning equipment was not yet available for a native ST 2110  I/O design, necessitating the expensive addition of 24 processors to position captions accurately.

Audio Design

An audio production console based on ST 2110 standards was selected for its ability to reroute streams natively without conversion to other commonly used audio formats such as MADI or Dante. Audio-only devices interfaced directly with the “red” or “blue” audio aggregation leaf switches via 1 Gigabit Ethernet interfaces.

PTP Timing and Synchronization

Redundant Precision Time Protocol (PTP) grandmaster clocks locked to satellite signals -- the “heartbeat of the system” – were implemented in the design of the media network architecture. A proper PTP design is crucial to ensure precise synchronization of the various RTP video, audio, and ancillary data streams in an ST 2110 system.

Training

The design and integration team established a training program to help overcome any anxieties of the station engineering staff in moving to IP-based technology. Training began with a basic TCP/IP and networking course. As the ST 2110 systems became operational, vendors of the router control, network hardware and other systems came on-site to offer equipment-specific instruction. SMPTE’s own virtual course, “Understanding SMPTE 2110” was also a key part of the training program.

As of early 2022, the new facility has been operational 24/7 for more than six months and continues to perform well. Jim Beahn and Nik Kumar report that all parts of the system work as designed, making the effort to overcome the numerous challenges well worth it.

For a closer look at the implementation of this leading-edge technology, read the complete article in this month’s SMPTE Motion Imaging Journal.

Keywords: SMPTE, Media over IP, ST 2110, ST 2022, SMPTE standards, SDI, serial digital interface, RTP, realtime transport protocol, PTP, precis