05.01.2003 12:00 PM
Originally featured on
Master control playout options

At any broadcast station, the final stop before the transmission chain has always been master control. Its function is simple: string programs, promos, commercials and emergency messages together into a compelling stream so that viewers should find no reason to leave to watch other channels. The programs are clearly the meat of this sandwich. But every station wants to deliver the whole sandwich, including interstitial content to generate revenue and, in the case of promos, to draw viewer interest to upcoming offerings.

Master control at the NBC Miami ShareCasting hub in Miramar, FL, is based on Florical technology. The facility originates broadcasts for NBC O&O stations in Miami (WTVJ), Dallas (KXAS) and Birmingham(WVTM), as well as the NBC-owned Miami Telemundo station (WSCV).

A brief look back

Broadcasters are familiar with the history of the technology required to accomplish this task. At one time, all material played from film. Eventually, videotape replaced film, and videotape players of all types came into use, including robotic loading systems like Betacart, Ampex ACR-25, RCA TCR-100, Sony LMS and Flexicart, and Panasonic MARC and Odetics robots as well. These robots simplified and improved the reliability of air operations and reduced labor costs, but they also represented a slightly different way of delivering the same events to the switcher that concatenated the segments together. It was a parallel approach, with master control requiring more than a dozen sources, and perhaps many more, to achieve the goals of the programmers. Many small segments (promos and commercials) meant many individual players, which, together with character generators, still stores, network sources and satellite receivers, resulted in a large and relatively complex switching system. Such systems were, and are, designed to be highly flexible and easy to operate, either manually or under the control of an automation system. But one single development more than a decade ago changed the fundamental requirements completely.

Enter the server

The invention of the video server began to eliminate most stand-alone VTRs and cart machines for interstitial playback. Servers offered several critical and defining differences to the state of the art when they were introduced. First, they were capable of concatenating many segments internally and playing them out seamlessly on a single output. Second, they could hold an entire station's library of promos and spots online all the time, eliminating the need to have VTRs play back short-form material. Third, they were capable of tight integration with automation, allowing selection and playout of interstitials without operator intervention. The Holy Grail of broadcasters these days is reduced cost, and servers move us closer to the day when fully automated acquisition and playout might be a reality.

But there is debate about the form master control should take for different applications. For instance, when live programming is a major portion of the program schedule, a manual operator interface is clearly important. To the extent that servers can store all content and play it out automatically, a manual interface serves primarily as a backup, making full-featured control panels less important.

Southern Cross Broadcasting’s Australian facility features Quartz Electronics’ QMC master control switchers.

Stand-alone solutions

Many manufacturers provide full master control solutions. These include Thomson Grass Valley (M-2100 and Saturn both remain in the product line after the acquisition of the Grass Valley Group by Thomson), Sony (Isara product line), PESA (MC Lite), Leitch (Opus), Utah Scientific (HD/SD-2020), Quartz (QMC), Ross Video (DVM series) and Chyron (Pro-Bel TX series). These switchers have multiple inputs, or use external routing to achieve multiple inputs to a stand-alone mixer frame. They can offer multiple keyers, squeezeback, audio over and other capabilities. They are, however, primarily switching and keying devices intended to work in environments where multiple sources are common, and stand-alone control panels are important.

Branding solutions

The other class of master control solutions is a little more difficult to define because the features of this class overlap those of stand-alone solutions. Perhaps we can best classify them as “branding solutions” because their primary purpose is to take a feed and apply effects such as supers, squeezeback, audio over and, often, internally generated character generator pages. Manufacturers supplying this type of system include Pinnacle (Dekocast), Miranda Oxtel (ImageStore 2-3) and NVision (NV5128MC). Some of these manufacturers also offer stand-alone control panels that extend their functionality to replicate the broader and more traditional type of switchers.

The Miranda Oxtel Imagestore at the master control room at WHRO incorporates all the functionality required in a master control chain in a single box, including AB mix, four key layers, logo generator, character generator, DVE, still store, clip-playout server, audio mix, audio store and EAS insertion. Photo courtesy of CEI.

Some offer software touch screen interfaces, and some offer only remote control through Ethernet or RS-422. NVision's system is so new that the manual control panel they envision is just not done yet, but the company notes that the system can be fully controlled without a manual panel in much the same way that others are currently controlled. Obviously, a manufacturer that doesn't supply a manual control panel intends the features to be primarily or wholly controlled by automation.


Over time, makers of automation systems have devised interfaces that control the full range of features in the solutions that have been around for a while, for instance, M-2100 and Saturn. When the new generation of branding solutions evolved, automation interfaces were hard pressed to easily control the broader range of options and operational modes they offered. It might well have been easier to offer multiple ports and control the basic functions from a standard interface using an existing protocol, and perhaps move the advanced features to another interface specific to the device. While that might speed software development, it is less than desirable for operational reasons. Who wants to have to parse transitions into more than one interface?

More appropriate is the development of an entirely new interface specific to the device, with all functions fully supported and called out in clear language that can be translated cleanly from traffic. This points out a significant shortcoming in the broadcast chain. To make complete use of the range of expanded capabilities such systems offer, traffic must have a lingua franca — a common language — in which to write the commands for translation to operations. For instance, if three keys are to be inserted and deleted at will, as many as three secondary events might be required in the air log. Take the case of a commercial break at the end of a program, with credits following before the interstitial station break. When you come back to the program, the bug might be inserted, the program squeezed back to reveal a character generator page, which advances to a second page, and then a logo is inserted. Each of these is a new event whose time relationship to the program must be defined in traffic. Then, individual commands must be translated into the automation system in ways that are predictable. Key One might be used for the bug, while Key Two is the character generator, etc. This careful definition of how the switcher is going to be run is a key element in the installation of the system.

Racks of Pinnacle DekoCast systems, installed in the new Starz Encore operations center, are used to automate interstitials, bug insertion and other on-screen branding.

In the past, most master control switchers had a simple RS-422 interface to automation. With branding solutions, you have to add other interfaces that add rich text, logos and other content to the air signal. A lower-third crawl for weather, school closings or EAS might be input to the system as a separate (or multiple) source(s) of data. The formatting of the datastream must be specific to the device, and it may need to be buffered if the text stream is not synchronous with the program content. The branding/master control solution may have that capability in it, and perhaps even multiple channels for that use.

The same, but different

There is as much variation in these systems as there is commonality. In general, they all do the same thing, but some of the systems do not offer key features. For example, unlike Dekocast and Oxtel ImageStore, some do not offer an internal character generator. In the past, manufacturers assumed that broadcasters would use a stand-alone character generator for such applications. But it is compelling to have the capability built into a more general-purpose system, assuming control issues do not become so thorny that the feature is hard to use.

Dekocast is inherently a character generator and graphics-based system. Recently, Pinnacle introduced an offline creation station to allow operators to create rich graphics without tying up the air channel of the system. This permits operators to composite complicated graphics and text and to fully preview them offline before delivering them to the air system to be presented and called up by automation.

Branding systems have another characteristic in common. In general, they offer no internal crosspoints; just a pair of inputs for foreground and background for transitions. Of course, two inputs are seldom enough, and they rely on external routing switchers for the crosspoints needed to fill out their capabilities. If the same manufacturer supplies the crosspoints, you can be pretty sure it will work. For many years, Thomson (BTS, Philips, etc.) has offered the Saturn system with internal and external crosspoints. NVision, Quartz, Miranda and others interface with routers they supply as well as with routers from third parties, often including their competition. If you are contemplating such an installation, ask the manufacturer very specific questions about the routers it supports and the complications that accompany each interface. One supplier recently told us it supported a specific router, but the cuts were not frame accurate when commanded from the master control solution.

The Thomson Grass Valley M-2100 master control switcher, installed at KVEA-TV in Los Angeles, offers multi-channel operation, extensive keying flexibility, separate and embedded internal digital-audio processing, and a wide range of software-enabled options.

Don't forget audio

While much of this article has pertained to the visual part of the master control chain, we can't forget audio. (Television without audio is merely surveillance.) Just as with pictures, the composition of the output stream from audio elements is no longer quite as simple as it once was. Master control used to contain an NAB cart machine and an input from a booth microphone for voice-over inserts. Today, a parallel solution might have digital playback from CD, MD disk, and .wav and/or .MP3 files from computers, all for integration into the final program. These may be interfaced with AES at 44.1kHz or 48kHz sampling, or analog mono or stereo audio. Program segments may have any of the above, and may also come with embedded audio, Dolby E or AC-3 audio for multichannel sound.

Some branding solutions have internal storage for audio elements as well. This leads to a rich environment in which the elements are sent to the MCR solution and the automation playlist calls up items as they are needed. Indeed, at least one manufacturer offers internal video playback as well, so complex moving logos, or even repeated promos, might be played without tying up the video-server channels. This adds another level of complexity to the traffic-automation interface.

Implementation considerations

Injecting a system like this into an existing audio (or video) plant requires careful planning. If there is no AES in the existing plant, you may need to convert both the input and output for monitoring and air signals. When using embedded audio, be sure not to compromise the audio-to-video synchronization. If you are contemplating using mixed audio sample rates, be sure the manufacturer supports this capability before ordering hardware.

Though the engineer who is accustomed to looking at the control panel in an analog facility might not think of it as even a potential problem, many modern master control switchers and branding solutions offer no separate audio metering, either on the panel or as a stand-alone external box. This presents no particular challenge, so long as you are aware of the need.

If HDTV is part of the implementation — which, today, is the case for many broadcasters — it is important to review just how the HD and SD versions of the system under review integrate together. In virtually all cases, the control panels available from manufacturers can seamlessly control multiple channels of HD and SD flavors. It is not quite as obvious if the HD version is different in subtle ways. If you want simultaneous switching, perhaps for simulcast programming, it is important to ask the manufacturer if its control panel can execute identical commands on two processors at the same time, and closely couple synchronization that you may need for upconversion of spots and/or content.

If you use an external router, mapping crosspoints to achieve the one-to-one match needed for “simulswitching” is not difficult. If the two switches are internal to the branding/MCR solutions, it may be necessary to restrict the inputs to both frames to have identical input maps. This will make one-to-one equivalency exact when using a single control panel. Doing so does not necessarily mean automation can handle the two streams with one set of commands. You must address that question to the automation company.

Looking ahead

DTV also can carry metadata, especially for control of an audio encoder. It is not clear just how future switchers will handle this. What happens to the metadata for two programs when you perform a dissolve between them? Does a cut in the datastreams work logically, or even electrically? If not, how would you reset values for DIALNORM and other critical parameters? Much work remains to be done in this area.

Lastly, what is the future of master control? One thing is certain: More can be done in computer environments today than ever before, and automation and master control are tightly coupled already. It is not hard to imagine a system in which the master control function is performed entirely in a video server with internal effects and keying capability. This is remarkably close to reality today, and at least two manufacturers (Harris/Aastra, and Leitch/AgileVision) offer systems that allow much to be done with the MPEG stream without decoding. While these DTV “master control” solutions are not loaded with all the features of other systems, over time we may see output streams concatenated together without “conventional” video hardware at all.

John Luff is senior vice president of business development at AZCAR.

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