CIARAN DORAN /
05.27.2004
Originally featured on BroadcastEngineering.com
Routing and control

For many years, manufacturers and broadcasters have pursued the goals of a completely integrated content environment, allowing efficient workflow and true shared access to both content and facilities. Streamlining production, processing, distribution and management of content throughout the whole content value chain is imperative in achieving that goal.

Therefore, it is strange that signal and control routing equipment, which has a crucial and strategic role to play, is often ignored. In modern broadcasting, the router traditionally operates at the core of a facility, ensuring every user has access to all the necessary signals without employing cumbersome patch panels.

Router developments

Router technology has never been glamorous, but advances in this often-undervalued technology have revolutionized the broadcasting industry. The video router delivered many advantages. Not only did it remove the confusing tangle of patch cords, but also reliability improved because there was no longer a physical connection that degraded with use.

Using a cross-point within the router, any source (input) signal could be programmed to pass to any destination (output). Multiple crosspoints for one source could also be made so that a single signal could now be routed simultaneously to several destinations. Multiple signals could be switched at exactly the same time (known as salvos), in the knowledge that all the levels would be synchronized.

The more sophisticated and larger that broadcast facilities became, the more the router evolved. Multiple-format routers with local or remote control panels, Ethernet connectivity with signal diagnostics and larger matrix sizes with built-in redundancy to ensure reliable signal back-up should anything fail have now become the accepted standard.

How they work

In digital television, long cable lengths can be added, and no difference is seen in the signal quality until a point is reached where, by adding only one or two meters, a cliff-effect occurs. Without warning, the signal has disappeared!

A reclocking router restores the original square-wave shape of incoming pulses and thereby enables the signal to pass over longer cable lengths, whereas non-reclocking routers pass the pulses without attempting to reshape or re-time the data stream. Switching signals while on-air or in record mode can cause undesirable visible or audible signal glitches.

A clean-switch router delays each signal according to its timing so that all output signals are sent in a continuous stream with the same alignment to a required reference signal. A continuous output stream is provided in which the video data content changes while the underlying transport stream is maintained in a continuous manner, delivering glitch-free operation. An AES quiet switch router operates similarly by providing crossfades between the signals to eliminate undesirable pops, clicks and large changes in the audio signal.

System control

The philosophy of the complete integrated content environment recognizes the value of routers as a key ingredient, binding all the elements of an installation into a cohesive and flexible unit.

Offering all the formats in all the sizes to cater for all possible requirements is not, however, the whole story. Control that is ultimately flexible, easy to use, easy to configure and designed so that it can be used both in a technical and an operational environment is crucial to delivering improved system efficiency. It is essential that interface systems operate seamlessly under the same control system — one that spans the complete range of infrastructure equipment and beyond.

Distributed architecture

Conventional routers relying on a central control system suffer from the inescapable flaw that if it fails, the whole routing system is useless. A distributed routing architecture also fails if the control system is not distributed as well. A truly flexible and redundant system is one that has both the routing and the control system distributed. In this way, there is no single point of failure, but instead a network of independent routers, each with its own on-board and redundant controllers.

In the world of routing, the trend towards smaller distributed routing architecture, where broadcasters are becoming increasingly reluctant to place all their risk within one router frame, means that a powerful control system managing all the networks is ever more important. With a flexible control system, users are no longer at the mercy of specific hardware control panels being in a different place from where they are needed, nor are they at the mercy of operational features designed-in by the manufacturer. With complete flexibility, users now have the freedom to implement a control system architecture designed for a specific working environment, all within the same control platform — whether in a highly technical engineering facility or a day-to-day working production studio.

Conclusion

As a broadcast facility grows, the importance of choosing the correct routing solution becomes ever more critical. A system that will deliver not only the practical connections of signal source/destinations, but also the operational efficiency integral with the reduction in operational costs sought by broadcasters, is essential. Routing, processing and technical and operational control systems must be considered together for broadcasters to achieve their goal of an integrated content environment.

Ciaran Doran is channel manager for Leitch Europe.



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