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Feature: Page (1) of 1 - 01/15/08

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Get Ready for the All Digital and HD Future of Broadcast

Station Infrastructure Considerations for the Analog to Digital Transition

By Jay Kuca

February 17, 2009 will mark the point of no return in the TV broadcast industry?s march toward an all digital future. On that date, all the high power analog transmitters will be switched off, leaving broadcasters little justification to continue maintaining the remnants of an ageing analog infrastructure.

The digital transition began well in advance of FCC?s 1997 announcement of this DTV timetable. The digitalization of video equipment has been underway since the early 1990s. Since then, the majority of cameras, VTRs, production switchers, and other studio equipment purchased employ digital processing, and probably have digital interfaces. They may also have analog interfaces as well, to facilitate their integration into legacy analog facilities. The majority of contemporary computer-based video equipment ? graphics systems, servers, and nonlinear editing systems, for example ? are inherently digital, and therefore virtually certain to have digital interfaces.

But what about the basic infrastructure of the station: the distribution and processing equipment, the core router, patch panels, and wiring? Newly constructed facilities or stations that have undergone a major rebuild in the last few years may have infrastructures that are predominantly or perhaps even 100 percent digital. But it is more likely that the station is built around a core that is either predominantly or perhaps even 100 percent analog.

During DTV?s transitional phase, an analog infrastructure has not been a serious liability. This is because the standard definition analog program service has been the station?s primary source of revenue. DTV viewership has been a small fraction of the total. However, when the analog shutoff occurs, stations will derive 100 percent of their revenue from their digital services. On February 17, 2009, DTV will cease to be a science fair experiment and become an essential, mission critical part of the business.

Due to limited DTV viewing audiences in the past, most facilities have made a minimum investment in system infrastructure so that they are ATSC compliant.  This is typically done by passing through local and network HD feeds directly to the DTV transmitter using a small HD router.

Figure 1. A system layout commonly found in the majority of current broadcast facilities. The main router/signal management system consists of analog or SDI video with mono or stereo audio. The station?s primary product is standard definition delivered through master control to an NTSC analog transmitter.

In addition to the shift from analog to digital program delivery, DTV is producing a shift in the balance of high definition versus standard definition programming and viewership. At many stations, the HD channel has been ?along for the ride.? But the rapid growth in the sale of high definition TV sets has produced a significant increase in consumer demand for HD programming. Program producers have responded by producing more programs in HD. In turn, competing program delivery systems ? terrestrial broadcast, cable, and satellite ? have responded by delivering more HD content to their viewers.

A major broadcast network has announced its intention to shift from mixed SD/HD to all HD affiliate program delivery in the fall of 2008. Given the savings in delivery costs, it is reasonable to assume the other networks will follow suit. This shift is a clear indication that the HD feed will be the primary program production and delivery format looking forward. If, when, and where SD is needed, it will be derived from the HD feed.

The other staples of a TV station?s schedule ? syndicated programs, locally produced news, public affairs programs, and commercials ? are also being produced increasingly in HD. Sometime in the not-too-distant future, the station?s primary channel will be programmed predominantly or perhaps exclusively with  HD content. As a clear indication of the extent of this trend, a number of stations who have recently constructed new ?greenfield? facilities have chosen to build them as 100 percent HD.

To be positioned to successfully compete in the future, serious consideration should be given to migrating as quickly as possible to a core infrastructure that is all digital, HD capable, and able to support the origination of multiple program streams.

Figure 2. The primary areas impacted in order to update the system to meet the emerging market demand for HD, the new primary product of the facility. The existing router core and small HD island will swap roles in system design along with the elimination of the analog NTSC transmitter.

The Routing System
The station?s routing switcher and its associated control system is the heart of the facility. The core router touches every aspect of the station?s workflow ? ingest, QC, program prep, production, post-production, and on-air operations.  Therefore, it is extremely important to map out an analog-to-digital migration strategy that ensures continuity of all station operations from start to finish.

If the existing core router is all analog or predominantly analog, serious consideration should be given to its wholesale replacement. At the very least, it should be augmented with an HD capable digital router large enough to handle all the station?s current digital sources and destinations. Be sure to choose a router platform that can be easily expanded to handle future growth.

Take into account the likelihood that over time the number of HD signals in the station will grow, and the number of SD signals will stay the same, or perhaps even shrink. Choose a routing system that is designed for all HD operation, that can be initially configured as a mix of SD and HD, and that can be flexibly expanded or reconfigured to handle future requirements.

In order for a router to be truly ?HD capable,? it must be designed for 100 percent HD operation with additional margin to spare. The entire crosspoint core must be able to handle signals with data rates of 1.5Gbits/sec and beyond. The frame, motherboard, and I/O system must be able to handle HD signals. The power supply system and cooling system must be able to provide the additional power and cooling required for HD.

In addition to HD and SD digital video, the core routing system may need to handle other signal formats as well ? discrete AES audio, or machine control, for example. Give careful consideration to selecting a router manufacturer who offers a range of products that handle all the formats you need.

The complexity of routing systems has grown dramatically over the last decade or so. A contemporary routing system is likely to handle a multiplicity of signal types and be controlled by a diversity of users, each with unique operational requirements. The complex task of managing the actual switching hardware in a ?user friendly? manner is the responsibility of the router control system.

Primary considerations in selecting a router control system include: the degree of flexibility it provides, the ease with which it can be configured and dynamically reconfigured, the number and types of control panels it supports, and the robustness of its design. The routing system is not very useful if it cannot be tailored to address the needs of the station, or if it cannot be relied upon to provide trouble-free 24/7 operation.

A secondary consideration for a router control system is how well it supports third party routers. This is especially important if there are legacy routers that will be kept in service.

The Master Control Switcher
The master control switcher is often referred to as the ?cash register? of the station, because its primary function is to manage the transactions (commercial insertions) that generate revenue. In the past, stations have had one revenue stream. In the DTV age, there will be multiple revenue streams.

Simple economics dictate the desirability to move from a single channel model to a multi-channel model without an undue increase in cost. To achieve this goal, any increase in either the capital equipment cost or the operating cost must be minimized. This translates into a low per-channel cost for the equipment, and holds any increase in operational cost to a minimum.

Figure 3. A state of the art DTV facility. The primary signal core is HD-SDI with 5.1 surround audio. Master control is multi-channel capable of delivering a DTV multi-cast to the DTV transmitter. The primary product is now HD with a down converted/ down mixed SD as the secondary product.

In order to avoid adding more operators ? with an attendant increase in operating cost ? automation is required. Stations that are not currently automated will either have to add operators or automate if they wish to program multiple channels.

In order to keep the per-channel capital equipment cost low, an alternative to the traditional approach to master control switchers is needed. The ideal system is one that has been architected with multi-channel operation in mind ? a modular system that supports multiple channels in a common platform.

The switcher electronics should be flexible enough to support a range of operational requirements. The primary channel may require a full set of features: switching, mixing, multi-level keying, logo insertion, and squeezeback. Secondary channels may require only basic functions like switching, mixing, and logo insertion. The switcher electronics should be scaleable enough to tailor the features of each channel accordingly.

Redundancy and hot swappable system components are also important considerations as downtime in master control can be very, very costly.

Signal Processing Equipment
It has many names ? terminal equipment, modular products, ?glue.? Whatever you choose to call it, the miscellaneous bits and pieces that tie the system together are of paramount importance in any facility.

Once upon a time, the lowly distribution amplifier was the most common element in this category. Today, it?s more likely to be complex functions like frame synchronizers, up/down/cross converters, and multi purpose products packaged on a single module.

When choosing processing equipment, it is best to identify one or, at most, two key suppliers. Every manufacturer has its own proprietary platform, module format, and control system. Mixing equipment from too many manufacturers in the same system can be costly in terms of both capital and operating costs.

Prospective suppliers of processing equipment should be evaluated on the basis of the technical performance of their products, the range of products they offer, and how well their products address the sum total of the needs in a particular system.

Comments About 3Gb/s
Chip manufacturers, equipment manufacturers, and organizations like SMPTE are working toward the development of components, equipment, and standards, to support 3Gbits/sec digital video. This data rate is needed to support 1080P/60 signals. This work is primarily of interest to the production and post production industries.

While it is unlikely that broadcasters will need to handle 3Gbits/sec signals inside their facilities, this technology does offer improved performance and greater operating margin for 270Mbits/sec and 1.5Gbits/sec signals. Interested readers should visit the Application Notes section of www.nvision.tv and read the white paper titled ?3 Gig Technology Improves Performance.?