Todd Riggs /
10.01.2009 12:00 PM
DTV broadcast routers
As routers grow in complexity, engineers need to understand the many possible options.

On the way to station consolidation, router sizes have exponentially grown. The model of sharing resources and talent within a single site or across multiple connected sites has the ultimate goal of technical efficiency, which includes minimizing the equipment footprint.

In-house routing systems are unique in this movement because they continue to grow in size. This article outlines the main reasons for this trend and discusses considerations for users as they make buying decisions for consolidated facilities.

Budget trends

The recession gripping the globe has impacted broadcast equipment purchases, but there is good news for those in the market for a new router. A down economy means fewer broadcasters are spending money, and end users are looking for attractive pricing and packages. This is especially true for projects requiring large routers.

End users are centralizing physical plant equipment, which means they are erring on the side of caution and buying bigger frames than they require right now. This provides enough space to expand sections of their routers for HD as more sources and destinations become available within the facility. Alternatively, broadcasters can use this additional space to house multiple formats in the same frame as they transition from a hybrid facility to a purely HD plant.

Multiviewer requirement

One of the biggest trends in routing over the last several years is the integration of functions and capabilities that have not been traditionally a part of the in-house router. Advances in both router hardware design and applications within hardware and software control panels have resulted in end users being able to control processing functions such as gain and EQ settings, among others. In addition, with the proliferation of multiviewers now available on the market, broadcasters are evaluating router purchases in tandem with new multiviewers.

Multiviewers have been a major factor in the increasing size of routers. Most new or rebuilt/updated facilities include at least one multiviewer in the design. When combined with the performance and operational costs of plasma displays and LCD panels, multiviewers offer the ability to modify layouts and provide tremendous flexibility for display in master control and production.

The multiviewer has affected router design in several ways. Two primary ways to physically connect a multiviewer to the routing system are internally within the router frame, or housed in external frames and fed via router outputs.

There are design considerations for both options. A multiviewer physically located inside the router frame is the most compact, cleanest and simplest option in terms of physical space, power and cabling. Operationally, this enables multiviewer picture-in-pictures (PIPs) to be switched as router outputs. This means that changing a source within a particular PIP is the same as routing a source to a standard router output. This is achieved via a standard router control panel, resulting in fast, simple and standard operation. When choosing this solution, end users should make sure the router frame is big enough to handle any increased multiviewer and/or router needs.

The other option is to locate multiviewers outside the router and feed them as external outputs. This option can be used in applications where cost is a primary concern, such as in simple quad splits or when a large number of screens are required, but only a minimal amount of sources require display. The design parameters when implementing this solution include being certain enough router outputs exist to feed the required number of multiviewers. This increases the overall number of router outputs, as well as space requirements for the external frames and extra cabling needed to physically connect the systems.

Broadcasters expect tight integration of the router control system, its hardware and software panels and the multiviewer, regardless of the physical layout. This allows the operator to treat the router and multiviewer as a single, integrated platform. Operations staff is often stretched thin, so router switching, multiviewer layout manipulation, PIP switching and “statusing” need to be possible from single control points, so multiple panels and software applications are most effective.

3Gb/s

No discussion on router trends would be complete without mentioning 3Gb/s and its impact on broadcast facilities. 3G routers are being considered for several reasons, including the fact that sources capable of delivering signals at this data rate are becoming more common. This could be a single-link 3Gb/s signal (Level A, higher-quality signals) or two 1.5Gb/s signals multiplexed into one physical connection (Level B).

Many facilities are beginning to also consider 3-D technology. A 3Gb/s-capable router is an important consideration for 3-D because these signals will require a higher-bandwidth system than traditional 1.5Gb/s systems. While there is no official standard for 3-D, the most prominent standard discussions involve the maximum data rates for 3Gb/s; therefore, a 3Gb/s-capable router will be able to support whatever standard emerges.

The other reason to consider 3Gb/s is that there are several vendors who offer 3Gb/s support at no price premium over 1.5Gb/s HD. Given the drive from camera, server and graphics manufacturers to support both 3Gb/s and 3-D equipment, it makes sense for broadcasters to buy equipment that can support these signals even if there is no current requirement for its use.

The bottom line is that most new HD-capable routers claim to support 3Gb/s, and a variety of test equipment can validate those claims. As a rapidly developing area in the industry, there are several things to consider when testing routers for 3Gb/s performance. Tests should be done across a sampling of all of the router's internal trace paths because the lengths vary within the system. It is inaccurate to assume that shorter paths will automatically pass if the longest path does. Each path will have slightly different characteristics, so it is important to gather a sampling of inputs to outputs to achieve accurate assessments of bit errors using 3Gb/s color bars and pathological signals.

Newer waveform monitors generally have higher bandwidth capabilities, so a broadcaster can receive different results based on equipment used. Viewing them through test gear will provide a good indication of the router's performance. Independent tests have been performed on most systems, and manufacturers can validate the performance of their products to assuage any potential concerns. Most can provide screen-shots of waveforms using the high-end oscilloscopes that are used in the design of the products. These will show even more accurate descriptions of jitter, rise and fall times, overshoot, undershoot and eye pattern opening quality.

Processing integration

While budget trends and multi-viewers have been embraced, processing integration is both the most exciting and the most challenging task. The integration of processing equipment (modular, card-based equipment) into the routing system has finally moved from discussion to reality. Almost every major router vendor is at least talking about it, and many have implemented the concept in some way. Some are already delivering products, and broadcasters are reaping the rewards.

Audio has been the initial focus, with manufacturers implementing technology to mux and demux audio coming into and leaving the router embedded within a video stream. Many of the questions and issues such as whether to implement an embedded or discrete plant and how to manipulate and shuffle previously embedded audio have largely been resolved, and the flexibility and troubleshooting advantages make this new technology appealing for both operations and engineering staff.

As efficiency increases, so does router control. As complex, multichannel audio continues to develop, the question of simple control for users is growing in significance. The manipulation and adjustment of parametric signal settings such as gain, summing, phase inversion and swapping are all accessible from single control surfaces, further reducing the possibility of human error.

This is just the beginning in terms of adding functionality. It is easy to foresee the integration of frame syncs, conversion gear, audio encoding and decoding, and other signal-processing components into modern routing systems. Intelligent, fast and intuitive workflows and interfacing are absolutely critical as more broadcast facilities experience a reduction in staff. The integration of new devices into a routing system is nothing short of a complete shift in how a broadcaster designs a facility or system.

This is a paradigm shift in more than just operations, because these systems also take up less rack space and use significantly less power, which reduces cooling requirements for equipment rooms; cabling requirements are also drastically reduced. This has practical benefits for just about every market segment, but especially in environments like mobile applications where weight, space and temperature are critical.

Broadcasters have a lot of factors to consider when purchasing a router that will work today and be ready for tomorrow. Routers continue to grow in complexity as more features come to the surface, and broadcasters need to both understand the various options and accept the learning curve that may come with them. More crosspoints and I/O per rack unit of space, with expanded feature sets including parametric control and integrated multiviewer support and integration, bring more for the operator to comprehend beyond simple switching. And with manufacturers charging an HD price for a 3Gb/s router, there is more reason to upgrade, especially with 3-D right around the corner.


Todd Riggs is a product manager for Harris Broadcast Communications.



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