Tying Systems Together
Oct 1, 2001 12:00 PM, By Mike Andrews
Each new trade show season heralds impressive advancements in the area of video and data display. The video projectors on the market now offer image brightness and clarity that would have required much larger and more expensive imaging devices only two years ago. Plasma displays have exploded in popularity: audiovisual professionals are exploring creative new applications for plasma products in home theaters, boardrooms, retail displays, hospitals, even train stations. As display technologies develop and mature, manufacturers are caught up in a productive cycle of competition and innovation that benefits the entire industry. A/V system integrators and end users now have more display options in every category and at every price point, from micro-portable projectors all the way up to large-venue displays.
These options will continue to proliferate. Displays based on LCoS are being introduced. HDTV is still in its infancy as a consumer technology, but each new generation offers improved image quality at more affordable price points. Working in concert with video scalers, rear-projection HDTV sets offer intriguing possibilities for large, high-resolution displays; and at some point we may see them break out of the home market and find new applications in the professional A/V world.
With all these options available, clients are demanding the ability to use one display device with a large number of input sources in several different video formats. Of course, this makes the systems integrator's job even more challenging. In order to handle all the signals that may be thrown at it, a display system should be flexible enough to accept signals in a variety of analog and digital video formats. Common analog video formats for standard resolution video signals include composite video, Y/C video, component video and RGBS. High-resolution sources such as computers, HDTV tuners and progressive scan DVD players will usually provide signals in RGBHV or progressive component video format. Digital video formats include SDI, DV and digital video interface.
The ongoing proliferation of signal formats has created the need for switching and conversion equipment that can make it easier to integrate all of them. The need to use multiple sources and formats with one display device is a key reason for the rapid acceptance of freestanding video scalers.
WHAT IS A VIDEO SCALER?
You might want to think of a video scaler as the video equivalent of an audio receiver. In many audio systems, the receiver accepts input from multiple devices: FM tuner, cable set-top box and/or satellite dish, CD player, DVD player, etc. On the rear panel of modern audio receivers, you'll find multiple inputs for analog audio as well as several different digital audio formats. The receiver allows you to select from the available inputs, adjust volume and equalization, and perhaps apply some signal processing. Finally, the receiver amplifies the audio signal and sends it to your speaker system. The receiver combines the functions of several separate devices, each dedicated to one of these signal processing, routing and distribution functions. A home audio system based on a receiver is therefore simpler, uses less rack space, and is easier to install, configure and troubleshoot, compared to one assembled of discrete components.
In a presentation system's video signal chain, a video scaler plays a similar role. Just as the receiver has become the single device of choice for most audio processing and routing, the video scaler is combining the previously separate functions of switching, signal conversion, signal enhancement and control.
TYPES OF SCALERS
Let's start with this entry-level product, the basic video scaler. These accept one or more standard resolution NTSC or PAL video signals in the composite, S-video (Y/C) format. Many video scaler models include component video input compatibility, letting you take advantage of the high-quality signal format found in DVD players and many industrial and broadcast-grade video sources. Just this year, a few scaler models began to support serial digital interface inputs, providing a superb digital connection to high-end video sources that feature an SDI output. Some scaler models also provide a passive RGB input that can accept a computer video signal from a laptop or other presentation computer and route it passively (without scaling) to the scaler's output.
These take in computer signals at various resolutions and refresh rates and then output them at the ideal resolution and refresh rate for your display. RGB scalers can therefore take in a lower resolution signal such as 800 by 600 and scale it up to 1024 by 768 to match the native resolution of the display. Some RGB scalers can also downscale the image, taking a 1600×1200 input signal, for example, and outputting it at 1024 by 768. While many display devices have some RGB scaling capability, RGB scalers often do the job better and handle a wider variety of computer signal resolutions.
The up and down scaling capability of RGB scalers makes them invaluable in a number of ways. First, they often provide better quality scaling than the built-in scaling in the display device. They also make it possible to take in a wider variety of computer signal resolutions. Some RGB scalers even offer component video output in HDTV-compatible formats such as 480p or 1080i.
Combine the features of the two previous scaler categories, and you get a means of connecting a variety of standard-resolution video sources and high-resolution computer video signals to one display. These make it easy to select between signals and output all signals at the ideal resolution for the display.
A special variant of the video scaler that includes several video inputs and one or two passive computer inputs, seamless switchers provide glitch-free transitions between a selected computer input and any of the video inputs.
At the top of the price and capability spectrum are these all-in-one models. They accept both standard-resolution video and high-resolution RGB signals, convert and enhance them as needed, and switch between sources on the fly with graphics-enhanced transitions including wipes, fades and other 2-D or 3-D effects. They do all of this in response to real-time operator control.
WHY USE A SCALER?
Many display devices have multiple inputs and signal conversion capabilities, so it seems fair to ask why video scalers are needed at all. If you're a typical presenter on the move, you run everything off a laptop and use an ultra-portable or micro-portable projector. In this case, a video scaler would be excess baggage. However, many other display system applications will benefit from the addition of an external video scaler. There are five primary reasons for including scalers in your display system designs: display device signal compatibility, enhanced signal management, simplified system design, optimized video processing, and future-proofing.
Data Display Signal Compatibility
As data displays of all types find new applications, there is an increased need to convert standard resolution NTSC or PAL signals in the composite, S-video or component video format to a VGA-type signal that is compatible with most displays. Data monitors and LCD flat panels are commonly used in computer classrooms, installed in podiums for presenters, as control room/backstage cueing monitors, or even as evidence presentation displays for the judge, witness, counsel and jury in a courtroom. While large displays such as presentation monitors, plasma displays and data projectors usually include composite and S-video inputs, desktop CRT monitors and the more economical LCD flat-panel display models usually only have an RGBHV input. Using a video scaler to composite, component, and S-video formats to RGBHV progressive video, you can display any sort of video or computer signals, regardless of the original signal format.
Enhanced Signal Management
Video scalers can accept a large number of formats, so they give your system more flexibility than it would have if you relied on the display device's signal management functions. Scalers routinely accept composite video, S-video (Y/C) and component video signals; and some recent models also handle progressive component video, RGBHV/RGBS/RGsB analog computer video and even DVI digital video. Having these functions in a separate device allows you to update the system's input capabilities by exchanging a rack component, rather than swapping out the display (typically the most expensive single element of the A/V system). While higher-end projectors and displays may accept many of these signal formats, some of the more economical models may not include the type or number of inputs required to support your needs.
Most video scalers can also serve as medium-capacity switchers, since they now routinely include from four to eight inputs for video and audio. Video scalers can accept video and computer video signals in a variety of formats and resolutions and output any of them at a resolution, refresh rate and format that delivers the best available image from your display device. This simplifies system integration and design. In most cases, it is much easier to connect all of the sources to the video scaler, use it to select the desired source, and then connect a single RGBHV cable to the display. That design is usually more efficient than connecting individual composite, S-video, component and RGB lines to the projector and then switching the projector between inputs.
Video scalers are now offering many video output formats, allowing the flexibility to connect to more types of displays. In addition to the RGBHV signal format popular for data displays, scalers may also include a progressive component output for connection to HDTV displays. The newest scalers may also include a DVI output. By making a direct digital connection between the video scaler and the display device, you can bypass the D-to-A conversion circuits in the scaler and the A-to-D conversion stage in the display device. Direct digital connections produce superior image quality.
Optimized Signal Processing
Because video scalers are designed solely for decoding, converting and scaling signals, you will often find that you can achieve better video image quality by using an external video scaler with your display device. In addition to advanced decoding and scaling capability, some video scalers include sophisticated circuitry that identifies the original source material for video sources and automatically applies a motion compensation formula to eliminate artifacts. When working with computer video signals, you may also find that scalers with RGB scaling capability will upscale computer video using more DSP power and more sophisticated algorithms than the scaling included in the projector or data display; therefore, image quality can be significantly better.
Video playback devices and transmitted sources, as well as computer display formats, are still evolving and improving. So are display technologies and the products based on them. At the same time, many of your clients will have significant amounts of archived material stored in older formats. Including a standalone video scaler as part of the system makes it easy to deal with changing input and display technologies. For instance, you can use a scaler to accommodate new source formats without the time and expense involved in installing a new display device. Conversely, if new display technologies become available (as is likely to happen following the acceptance of HDTV devices by consumers) it's a lot easier (and less expensive) to upgrade the video scaler along with the display than to replace several different playback devices and all of their associated media.
VIDEO SCALER APPLICATIONS
As audiovisual system designers compete to deliver the best solution for each customer, video scalers will continue to be an important system integration tool. Scalers can help you design and install display systems that offer excellent image quality. A standalone scaler gives you and your client the flexibility to handle a large number of current videosources and an easy, inexpensive, backward-compatible upgrade path to formats of the future.
While video scalers originally achieved popularity in the home theater environment, they are currently used in a variety of display and AV system applications including conference rooms, training rooms, classrooms, boardrooms, lecture halls, computer training labs, retail displays, museum displays, information kiosks, theme parks and entertainment venues, houses of worship, theaters and performing arts venues, rental and staging systems, briefing rooms, command and control facilities, network operations centers and courtrooms.
To give you an idea of how scalers fit into today's audiovisual systems, let's look at some actual applications.
Courtrooms require clear output from diverse sources. In a jury trial, presentation of exhibits as evidence to the jury can take longer than the deliberation process. Systems like ExhibitOne Corporation's TrialView Evidence Presentation System are designed to facilitate the presentation of evidence and information during trial proceedings. The courtroom requires a great deal of flexibility. Evidence might be presented from either counsel table or from a special lectern. The audience for any particular piece of information might be the judge, the jury, a witness or opposing counsel. A laptop computer might generate the video signal, or it might emerge from a VCR playing either a VHS or S-VHS cassette, or from a stand-mounted video document camera. All of these options must be controlled from the judicial bench since the judge is the ultimate arbiter of what the jury sees. Courtrooms demand a high level of display quality. Whether the jury is reading a document, looking at a diagram or viewing video footage, monitor resolution is critical.
The video scaler can handle all these requirements. It responds to control signals from the judge's bench, routing the video signal wherever the judge decides it should go. Display devices range from 15-inch flat-panel LCDs to large-screen presentation monitors and projectors. The scaler accommodates a wide range of sources and delivers optimum detail and viewing quality, which is critically important when a piece of video or a computer-generated diagram or chart might sway the outcome of a trial.
Lecturers need to see the image, too. Video projection use is increasing in lecture halls, training facilities and classrooms. Because these rooms are expensive to build, they're often designed to handle a variety of functions, from computer slide shows given by live presenters to video conferences or distance learning presentations. Multifunction means multiple video and RGB sources. It's much simpler, and in the long run more versatile, to connect a scaler's single output to the display device and route all the sources through the scaler. In a large facility with long cable runs, it's also cheaper to do it this way.
There's another benefit of using a scaler: While optimizing the image for the audience, a scaler can deliver a high-resolution image to the podium. It's not uncommon today to conceal a 15-inch flat-panel display in the podium. In combination with a video scaler, the display gives the lecturer a brighter, crisper image with a wider viewing angle than would be available from most laptops. All of those factors will allow the presenter more freedom to engage the audience instead of trying to decipher a new slide.
Houses of Worship
In larger houses of worship that seat over 800 people in the main auditorium or sanctuary, it's often necessary to use multiple projectors to provide a viewable image to the entire congregation. In the experience of Shepherd Ministries of Dallas, Texas, which designs and installs multimedia systems for a wide range of religious organizations, source material typically comes from VCRs, DVDs, cameras, satellite or cable networks, and computers. These are all connected to a video scaler, which converts everything to a VGA or XGA computer RGB format. The video scaler in turn feeds a distribution amplifier or twisted pair transmitter, which can send multiple copies of the signal over long cable runs to the different locations in the building where it will be displayed. Without the scaler, the congregation would be distracted by the change in quality and resolution of the projected images. With the scaler, they focus on the message, not the medium.
GROWING IN IMPORTANCE
Video scalers are a relatively new type of tool in system integrators' kits, but they continue to grow in both usefulness and functionality. As video broadcast, transmission and playback sources continue to proliferate and computer displays evolve, video scalers help the audiovisual system keep pace with innovative developments. As manufacturers continue to add functionality to video scalers, they are becoming more and more capable of being the central control point for both simple and complex audiovisual systems.
Mike Andrews is the vice president of marketing for Inline Inc. Video scaler application background material was supplied by Jim Martin, MCSi; Kevin Sandler, Exhibit One Corporation, Chandler, Arizona; and Josh Lyons, Shepherd Ministries, Dallas, Texas.
Video Scaler Functions: The Basics
A scaler accepts an input signal in one format and outputs it in another. For instance, you could connect a VHS player with analog composite output, and the video scaler would output the images as digital component video. Without the scaler, you might not be able to present archived video effectively on a new large-screen projection system that delivers its best performance with a DVI signal.
A video scaler can enhance signal resolution (once known as line doubling). An NTSC video signal, for example, is divided into 400 horizontal lines, but modern display devices can show two or three times that many. Whether you're magnifying an image to auditorium scale or shrinking it to fit on top of a podium, scalers can interpolate the lines that are missing in the source to enhance the resolution of the signal. They're not limited to doubling or quadrupling, but perform complex calculations to convert, say, an older laptop's screen resolution of 800 by 600 to 1024 by 768. A scaler can also downscale high-resolution computer signals.
Switching and Control
Scalers give presenters the ability to choose which sources to display and where. Again, these functions used to be performed by separate devices but have been incorporated into the video scaler. Some scalers are beginning to incorporate other functions by enhancing the basic switching capability.
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