SDI has served as the foundation of both SD and HD video solutions, with characteristics that have been enormously valuable in supporting and shaping the evolution of broadcast and production workflows. Deterministic behavior and fixed low latency, for example, enables the frame accuracy and synchronization that is critical in live and studio production environments, where the mixing and switching of many signals yield the final product. As facilities move to IP, they want to hold onto these benefits of SDI while shedding its limitations. Their goal is to get SDI-like performance out of IP in specific scenarios, and also to enjoy greater connectivity and greater agility in addressing the challenges of multiplatform content creation and delivery.

While the true IP-based facility is still a work in progress, it is only a matter of time before it becomes a reality. Developments in network technology are lending themselves to the replacement of SDI-dependent products with IP solutions capable of moving high-bitrate, uncompressed signals alongside compressed signals. As we push toward all IP solutions, SDI still has its place and will for some time, but only when legacy or surrounding infrastructure demands its use.

Once a broadcast facility moves “beyond” the hybrid model that still relies heavily on islands of SDI functionality, IP technology will enable scaling in many ways to accommodate a rapidly changing media ecosystem. In addition to providing a single connectivity medium for all content, this shift will enable use of network equipment – much or all of it commercial-off-the-shelf (COTS) – including interface cards and switches to create the appropriate environment and support workflows, including production and playout, where SDI plays a key role today.

End-to-End IP Infrastructure

Already, IP is firmly established at the distribution end of broadcast workflows and enables OTT, VOD and CDN delivery of content to consumers. It makes sense that all workflows and as much of the delivery infrastructure as possible are rooted in the IP realm.

Although encoding and transmission for linear scheduled services today rely on network infrastructure, the upstream workflow steps of playout and some aspects of production present stringent timing requirements for synchronous video that — at odds with best-effort, asynchronous IP carriage and processing as the industry has known it — are a significant challenge to establishing operations on IP infrastructure.

Interoperability with respect to interfacing, encapsulation, switching, timing and management is critical, and adherence to standards will be essential not only to interoperability, but also to the industry-wide viability of media over IP.

With no clear winner so far in terms of standards (or sets of standards) used to establish IP-based operations, pioneering broadcast facilities may need to make fundamental infrastructure decisions without any guarantee that their standards of choice will be universally adopted. That said, an array of standards and approaches to IP from SMPTE, VSF, EBU and other bodies are being championed in various forms by groups such as AIMS, ASPEN and NMI.

Key Standards/Encapsulation Approaches

SMPTE has been at the forefront of standardization of video carriage in an IP domain, and SMPTE 2022 currently addresses both uncompressed video data and compressed video. To overcome the limitations of IP, SMPTE 2022 specifies appropriate forward error correction (FEC) schemes, along with seamless protection switching. As a result, SMPTE 2022 is an effective bridge between the worlds of SDI and IP. When implemented with stream redundancy, SMPTE 2022 goes a long way to replicating SDI capability in IP networks. To standardize video over IP, VSF has built on SMPTE 2022 with its technical recommendations TR-04 and TR-03 in an approach that comprehensively addresses the needs of production for video in an IP domain. This includes support for splitting video, audio and metadata and resyncing of sources into a final output.

While AIMS promotes the adoption of these VSF recommendations along with standards proposed by SMPTE and AES, the ASPEN group promotes an essence-based packet approach that allows video, audio and metadata to be routed and processed individually. Sony’s Networked Media Interface (NMI) combines SMPTE ST 2022 video transport standards with SMPTE timing synchronization protocols to support live production of video using IP networks. Though it’s possible that no single approach will prevail, these efforts promise to guide and simplify the use of standards to transition to IP-based operations.

Compression Schemes in the IP Facility

Routing uncompressed video over networks is sometimes not a practical proposition, particularly in the case of UHD, which will not fit in over 10G network connection. Compression can be a key enabler for the transport of media over IP, and particularly existing 10G networks. A new breed of mezzanine compression schemes offers visually lossless compression together with very low latency coding. Advances in efficiency and suitability of compression schemes including VC-2, TICO and LLVC, when networked in production environments allow mild compression schemes to be used as a near-transparent alternative, using less bandwidth when compared to an uncompressed approach.

As well as streaming of media to replace SDI with IP alternatives, there continues to be a growing number of new compression schemes used in electronic newsgathering (ENG) and other ingest and playout centric workflows. For example, Sony’s XAVC and Panasonic’s AVC-Ultra are new codecs that allow cameras, editors, video servers and transcoding systems to store, manipulate and share content with resolutions up to and including UHD. While carriage over networks of the files generated by these codecs and their forefathers is non-real time, they do form part of the fabric of IP facilities that has been in place for many years now. Non-real time and real time media streams sharing a common network infrastructure becomes a design choice. Irregular flows of non-real time media transport demands have an impact on a shared network topology when balancing the requirements to sustain continuous real time streams.

4K/UHD Over IP Networks
For the time being SDI has a role to play in the rollout of 4K and UHD. Consensus is growing around the future of UHD being delivered over IP networks. Through efforts to accommodate 4K and UHD, SDI has been deployed using four 3G links. Supporting UHD over a single cable in SDI requires 6G, 12G and even 24G variants. Ultimately, however, SDI seems to be giving way to IP as the preferred long term approach. For the time being broadcasters are willing to live with 4x 3G SDI connections to deliver practical working UHD solutions.

The industry has made significant progress in implementing IP for HD workflows, and new 40G and 100G Ethernet variants are opening up the possibility of uncompressed carriage of 4K/UHD. As these options become less costly, they will help drive the industry to overcome the limitations of IP for the carriage of real-time video.

Many broadcasters will not undertake an IP-based facility refresh until they have greater clarity on the future of 4K/UHD. Delivery of 4K/UHD to the home is ramping slowly. Even though the use of 4K/UHD mezzanine formats to future-proofing assets has grown in popularity, there is still a relatively limited amount of content available to drive a significant number of channels. 4K/UHD does seem poised to gain significant momentum and this will fuel demand for IP-based production solutions that support standardized 4K/UHD production workflows.

Conclusion
Although continued standardization efforts and further evolution of media technology are needed for the broadcast industry to fully realize SDI-free workflows, IP is on its way to domination. The hybrid facility will remain a reality for many broadcasters as they transition to an IP infrastructure, but this coming year we can expect to see all-IP facilities being built using standards that will entirely replace SDI and change the mechanisms by which content is produced and delivered.