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Media Transitioning from SDI to IP to Increase Agility and Efficiency

As the delivery and distribution of content has changed, so, too, has the infrastructure and technology needed to meet the ever-changing needs of consumers. At the top of that transition is a shift from Serial Digital Interface (SDI) to Internet Protocol (IP).

August 31, 2020 9 minute read

It's not hard to see how the broadcast industry has changed in just the last few years. As over-the-top companies continue to innovate in how they deliver media and content to consumers, legacy media organizations are faced with an increasingly pivotal choice: attempt to adapt or fall behind.

This article provides a brief overview of the transition from SDI to IP, what each technology is, why the move is necessary the challenges media organizations may face when making the switch and how WWT can help with that transition.

What is Serial Digital Interface (SDI)?

Established in the '90s, Serial Digital Interface (SDI) has been the standard transportation method used to carry video and audio signals. Its point-to-point unidirectional link was designed to replace older analog composite and digital parallel links.

SDI is not routable in the same sense as Internet Protocol (IP), the newer transport method for digital media that operates on over IP networks. Instead, SDI is circuit switched using video routers, which still dominate the existing equipment install base for video production.

Why the switch from SDI to IP?

As vendors are choosing to build native IP endpoints and replace SDI routers with data center IP switching fabrics, most media companies are likewise looking to transition their endpoints and video routers from SDI to IP.

One of several media industry organizations overseeing this transition is the Society of Motion Picture and Television Engineers (SMPTE). SMPTE has published a family of standards (i.e., SMPTE ST 2110-xx) defining how aspects of this transition should be handled, leveraging many of the existing IP technologies used by the Information Technology (IT) industry.

A screenshot of a cell phone

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A high-level diagram of the what is meant by ‘SDI to IP transition.’

What are the benefits of IP?

Many industries are transitioning their business infrastructure to Internet Protocol (IP) class hardware and software for the flexibility, scalability and the ability to create new and unique services not available with legacy infrastructure.

This transition allows organizations to unlock a new ecosystem of vendors that can lead to best-of-breed solutions to satisfy specific business objectives from a production and creative standpoint.

IP enables the seamless movement of content between the field, studios, central technical facilities, control rooms and the direct publishing to popular social media networks, such as Facebook, Twitter and YouTube.

Other benefits of IP include:

  • Video infrastructure can leverage IT infrastructure’s falling cost curve for higher performance.
  • Transitioning to IP tends to consolidate services, thus removing traditional business silos businesses and driving efficiency and cost savings.
  • Because IP links typically use fiber, fewer cables and less space are required for the same capacity. For example, a single 10 Gbps fiber link carries six 1.5 Gbps HD signals, as compared to six coax SDI cables. Fewer cables means less complexity, project management and installation time, resulting in lower total project costs.
  • IP links carry bidirectional traffic, meaning endpoints can have both inputs and outputs. For example, camera control input signals can be received over the same cable as the audio and video output.
  • Because video, audio and ancillary signals are IP addressable, these signals can be routed to anywhere there is an IP network with sufficient bandwidth and an IP endpoint. For example, with an IP-enabled camera in tow, a camera operator can work an event from anywhere. This also removes any need to embed or de-embed audio or metadata within the SDI infrastructure.
  • Native IP endpoints can more easily move to higher bandwidth services. For example, an IP camera can move from HD to UHD resolutions without a fork-lift upgrade of the IP infrastructure.
  • With IP, Precision Time Protocol (PTP) is leveraged for in-band signal synchronization, which eliminates the need for SDI's legacy out-of-band timing mechanism (e.g., Black-Burst timing tree).

What are the challenges of transitioning from SDI to IP? 

When businesses transition to IP, hardware, software, business functions and services need to converge and work seamlessly. This may require redefining how work flows through the business and a possible reorganization of responsibilities among stakeholders

The technology shift to IP also means operators need new skillsets to design and manage the network.

As endpoints move to native IP interfaces, interoperability must be tested and validated before moving endpoints into production. The any-to-any nature of IP requires careful design when it comes to securing digital assets and their restricted routing to authorized personnel, endpoints and services.

How does IP-based infrastructure work?

As SDI routers are supplanted by data center-class switches using a spine-leaf network switching fabric design, inherent in this design are tried and true IP technologies like:

  • IP routing protocols for dynamically building the routing table for endpoints to route signals to each other.
  • Internet Group Management Protocol (IGMP) and Protocol Independent Multicast (PIM) protocols for the routing of signals from one to many endpoints, a process used extensively in the broadcast environment.
  • PTP for distributing timing in-band for sub-microsecond endpoint synchronization and Software-Defined Network (SDN) controllers for managing the switching fabric.
A view of how media streams traverse the spine-leaf switching fabric of IP-based infrastructure.
A view of how media streams traverse the spine-leaf switching fabric of IP-based infrastructure.

What technologies are required to transition from SDI to IP?

Several hardware and software technologies are required to route media streams between endpoints and seamlessly replace the SDI video router. Data center-class switches are connected in a switching fabric with underlying IP software features enabling the flow of media streams.

Hardware

Data center switches are purpose built for the high bandwidth, high availability and low latency non-blocking packet switching of mission critical data. They typically are deployed in a two-tier (leaf-spine) switching fabric. The data center switch performance, price points and support service vary from vendor to vendor. Support services include four-hour to next business day hardware replacement, software upgrades and feature licensing, and phone troubleshooting support to sending engineers on-site for network issue resolution.

A switching fabric is a network topology in which network nodes interconnect via one or more network switches arranged in tiers or stages. The switching fabric may or may not have a Software-Defined Network (SDN) controller to manage the switching of traffic in the switch fabric. In the broadcast environment, a broadcast controller often orchestrates the media flow between the endpoints and the switching fabric via Application Program Interfaces (APIs) on the SDN controller or on the switches themselves.

Software

Routing protocols are used for exchanging routing information between switches. This routing information is based on IP and is used to route IP media flows between endpoints. Specific examples of routing protocols used within the switching fabric include Open Shortest Path First (OSPF), Border Gateway Protocol (BGP), Intermediate System to Intermediate System (IS-IS), Enhanced Interior Gateway Routing Protocol (EIGRP) and others.

Internet Group Management Protocol (IGMP) is a communications protocol used by endpoints and adjacent switches on IP networks. Endpoints use IGMP to join and leave specific multicast groups. Multicast groups can be thought of as a video, audio or metadata channel that can be in their own individual groups or combined together into a single multicast group. IGMP is an integral part of IP multicast and works hand-in-hand with PIM.

Protocol Independent Multicast (PIM) is a family of multicast routing protocols that provide the one-to-many and many-to-many routing of IP media flows over the switching fabric. It is termed “protocol-independent” because PIM does not include its own topology discovery mechanism but instead uses routing information supplied by other routing protocols mentioned above.

Precision Time Protocol (PTP) is a protocol used to synchronize clocks throughout the switching fabric to a clock accuracy in the sub-microsecond range. A Grand Master clock, typically referenced to GPS, provides the switching fabric and connected endpoints with their PTP reference clock. The switches may act as an ordinary master clock (i.e., not Grand Master), transparent clock or boundary clock to their connected devices. Time stamping happens as PTP packets traverse each switch, allowing the endpoints to synchronize time with the Grand Master clock.

Software-Defined Network (SDN) Controller is an optional but often recommended component for managing the media flows traversing the switching fabric. It is useful for simplifying fabric configuration, monitoring the fabric’s health and troubleshooting. The SDN controller also provides northbound APIs that a Broadcast Controller can use to manage the switching fabric.

Partnerships will be key to transitioning to IP 

As traditional broadcast technology transitions to IP, there are many complexities to consider, such as the network design and equipment choice specific to the media's specific requirements, the choice of COTS hardware and hypervisors to host virtualized media applications, storage and the strategic migration of services.

WWT brings many years of experience in the IT space and has created a broadcast media focused team to help media customers make this transition.

WWT's Advanced Technology Center (ATC) allows customers to test their proposed solution to ensure successful deployment. Once validated, organizations can leverage our 4 million square feet of logistics and integration space, spread over four continents, to deploy solutions at scale and on time.

Further, WWT can help media companies:

  • Verify that the correct equipment is ordered for the application, navigate the manufacturer’s ordering process and get the best pricing.
  • Provide network design or review to ensure manufacturer compliance.
  • Provide technical training or ideation workshops to work through challenges.
  • Build and test racks or centrally stage equipment to customer specifications to be shipped anywhere in the world.
  • Decide on a manufacturer, architecture and integration strategy that fits into their implementation timelines.
  • Provide professional services to help plan, design and implement customer projects.
  • Find the right talent to augment your technical staff.

Conclusion

Today, the broadcast industry uses Serial Digital Interface (SDI) to transport video and audio signals within a production broadcast environment, with the SDI router being a central component used to route video, audio and ancillary data.

As this environment converges to IP, the network will essentially serve as the video router, allowing for more dynamic production video workflows as well as lower total cost of ownership.

As the broadcast market makes the transition to IP, WWT has invested in creating a media-focused team, extensive test labs and large logistics operations to help organizations transition to this new world of IP-based media and entertainment.

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