Tying Systems TogetherEach 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 10/01/2001 8:00 AM Eastern
Tying Systems Together
Oct 1, 2001 12:00 PM, By Mike Andrews
Each new trade show season heralds impressive advancements in thearea of video and data display. The video projectors on the market nowoffer image brightness and clarity that would have required much largerand more expensive imaging devices only two years ago. Plasma displayshave exploded in popularity: audiovisual professionals are exploringcreative new applications for plasma products in home theaters,boardrooms, retail displays, hospitals, even train stations. As displaytechnologies develop and mature, manufacturers are caught up in aproductive cycle of competition and innovation that benefits the entireindustry. A/V system integrators and end users now have more displayoptions in every category and at every price point, from micro-portableprojectors all the way up to large-venue displays.
These options will continue to proliferate. Displays based on LCoSare being introduced. HDTV is still in its infancy as a consumertechnology, but each new generation offers improved image quality atmore 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 outof the home market and find new applications in the professional A/Vworld.
With all these options available, clients are demanding the abilityto use one display device with a large number of input sources inseveral different video formats. Of course, this makes the systemsintegrator's job even more challenging. In order to handle all thesignals that may be thrown at it, a display system should be flexibleenough to accept signals in a variety of analog and digital videoformats. Common analog video formats for standard resolution videosignals include composite video, Y/C video, component video and RGBS.High-resolution sources such as computers, HDTV tuners and progressivescan DVD players will usually provide signals in RGBHV or progressivecomponent video format. Digital video formats include SDI, DV anddigital video interface.
The ongoing proliferation of signal formats has created the need forswitching and conversion equipment that can make it easier to integrateall of them. The need to use multiple sources and formats with onedisplay device is a key reason for the rapid acceptance of freestandingvideo scalers.
WHAT IS A VIDEO SCALER?
You might want to think of a video scaler as the video equivalent ofan audio receiver. In many audio systems, the receiver accepts inputfrom multiple devices: FM tuner, cable set-top box and/or satellitedish, CD player, DVD player, etc. On the rear panel of modern audioreceivers, you'll find multiple inputs for analog audio as well asseveral different digital audio formats. The receiver allows you toselect from the available inputs, adjust volume and equalization, andperhaps apply some signal processing. Finally, the receiver amplifiesthe audio signal and sends it to your speaker system. The receivercombines the functions of several separate devices, each dedicated toone of these signal processing, routing and distribution functions. Ahome audio system based on a receiver is therefore simpler, uses lessrack 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 playsa similar role. Just as the receiver has become the single device ofchoice for most audio processing and routing, the video scaler iscombining the previously separate functions of switching, signalconversion, 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 signalsin the composite, S-video (Y/C) format. Many video scaler modelsinclude component video input compatibility, letting you take advantageof the high-quality signal format found in DVD players and manyindustrial and broadcast-grade video sources. Just this year, a fewscaler models began to support serial digital interface inputs,providing a superb digital connection to high-end video sources thatfeature an SDI output. Some scaler models also provide a passive RGBinput that can accept a computer video signal from a laptop or otherpresentation computer and route it passively (without scaling) to thescaler's output.
These take in computer signals at various resolutions and refreshrates and then output them at the ideal resolution and refresh rate foryour display. RGB scalers can therefore take in a lower resolutionsignal such as 800 by 600 and scale it up to 1024 by 768 to match thenative resolution of the display. Some RGB scalers can also downscalethe image, taking a 1600×1200 input signal, for example, andoutputting it at 1024 by 768. While many display devices have some RGBscaling capability, RGB scalers often do the job better and handle awider variety of computer signal resolutions.
The up and down scaling capability of RGB scalers makes theminvaluable in a number of ways. First, they often provide betterquality scaling than the built-in scaling in the display device. Theyalso make it possible to take in a wider variety of computer signalresolutions. Some RGB scalers even offer component video output inHDTV-compatible formats such as 480p or 1080i.
Combine the features of the two previous scaler categories, and youget a means of connecting a variety of standard-resolution videosources and high-resolution computer video signals to one display.These make it easy to select between signals and output all signals atthe ideal resolution for the display.
A special variant of the video scaler that includes several videoinputs and one or two passive computer inputs, seamless switchersprovide glitch-free transitions between a selected computer input andany of the video inputs.
At the top of the price and capability spectrum are these all-in-onemodels. They accept both standard-resolution video and high-resolutionRGB signals, convert and enhance them as needed, and switch betweensources 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 toreal-time operator control.
WHY USE A SCALER?
Many display devices have multiple inputs and signal conversioncapabilities, so it seems fair to ask why video scalers are needed atall. If you're a typical presenter on the move, you run everything offa laptop and use an ultra-portable or micro-portable projector. In thiscase, a video scaler would be excess baggage. However, many otherdisplay system applications will benefit from the addition of anexternal video scaler. There are five primary reasons for includingscalers in your display system designs: display device signalcompatibility, 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 anincreased need to convert standard resolution NTSC or PAL signals inthe composite, S-video or component video format to a VGA-type signalthat is compatible with most displays. Data monitors and LCD flatpanels are commonly used in computer classrooms, installed in podiumsfor presenters, as control room/backstage cueing monitors, or even asevidence presentation displays for the judge, witness, counsel and juryin a courtroom. While large displays such as presentation monitors,plasma displays and data projectors usually include composite andS-video inputs, desktop CRT monitors and the more economical LCDflat-panel display models usually only have an RGBHV input. Using avideo scaler to composite, component, and S-video formats to RGBHVprogressive video, you can display any sort of video or computersignals, regardless of the original signal format.
Enhanced Signal Management
Video scalers can accept a large number of formats, so they giveyour system more flexibility than it would have if you relied on thedisplay device's signal management functions. Scalers routinely acceptcomposite video, S-video (Y/C) and component video signals; and somerecent models also handle progressive component video, RGBHV/RGBS/RGsBanalog computer video and even DVI digital video. Having thesefunctions in a separate device allows you to update the system's inputcapabilities by exchanging a rack component, rather than swapping outthe display (typically the most expensive single element of the A/Vsystem). While higher-end projectors and displays may accept many ofthese signal formats, some of the more economical models may notinclude the type or number of inputs required to support yourneeds.
Most video scalers can also serve as medium-capacity switchers,since they now routinely include from four to eight inputs for videoand audio. Video scalers can accept video and computer video signals ina variety of formats and resolutions and output any of them at aresolution, refresh rate and format that delivers the best availableimage from your display device. This simplifies system integration anddesign. In most cases, it is much easier to connect all of the sourcesto the video scaler, use it to select the desired source, and thenconnect a single RGBHV cable to the display. That design is usuallymore efficient than connecting individual composite, S-video, componentand RGB lines to the projector and then switching the projector betweeninputs.
Video scalers are now offering many video output formats, allowingthe flexibility to connect to more types of displays. In addition tothe RGBHV signal format popular for data displays, scalers may alsoinclude a progressive component output for connection to HDTV displays.The newest scalers may also include a DVI output. By making a directdigital connection between the video scaler and the display device, youcan bypass the D-to-A conversion circuits in the scaler and the A-to-Dconversion stage in the display device. Direct digital connectionsproduce superior image quality.
Optimized Signal Processing
Because video scalers are designed solely for decoding, convertingand scaling signals, you will often find that you can achieve bettervideo image quality by using an external video scaler with your displaydevice. In addition to advanced decoding and scaling capability, somevideo scalers include sophisticated circuitry that identifies theoriginal source material for video sources and automatically applies amotion compensation formula to eliminate artifacts. When working withcomputer video signals, you may also find that scalers with RGB scalingcapability will upscale computer video using more DSP power and moresophisticated algorithms than the scaling included in the projector ordata display; therefore, image quality can be significantly better.
Video playback devices and transmitted sources, as well as computerdisplay formats, are still evolving and improving. So are displaytechnologies and the products based on them. At the same time, many ofyour clients will have significant amounts of archived material storedin older formats. Including a standalone video scaler as part of thesystem makes it easy to deal with changing input and displaytechnologies. For instance, you can use a scaler to accommodate newsource formats without the time and expense involved in installing anew display device. Conversely, if new display technologies becomeavailable (as is likely to happen following the acceptance of HDTVdevices by consumers) it's a lot easier (and less expensive) to upgradethe video scaler along with the display than to replace severaldifferent playback devices and all of their associated media.
VIDEO SCALER APPLICATIONS
As audiovisual system designers compete to deliver the best solutionfor each customer, video scalers will continue to be an importantsystem integration tool. Scalers can help you design and installdisplay systems that offer excellent image quality. A standalone scalergives you and your client the flexibility to handle a large number ofcurrent videosources and an easy, inexpensive, backward-compatibleupgrade path to formats of the future.
While video scalers originally achieved popularity in the hometheater environment, they are currently used in a variety of displayand AV system applications including conference rooms, training rooms,classrooms, boardrooms, lecture halls, computer training labs, retaildisplays, museum displays, information kiosks, theme parks andentertainment venues, houses of worship, theaters and performing artsvenues, rental and staging systems, briefing rooms, command and controlfacilities, network operations centers and courtrooms.
To give you an idea of how scalers fit into today's audiovisualsystems, let's look at some actual applications.
Courtrooms require clear output from diverse sources. In a jurytrial, presentation of exhibits as evidence to the jury can take longerthan the deliberation process. Systems like ExhibitOne Corporation'sTrialView Evidence Presentation System are designed to facilitate thepresentation of evidence and information during trial proceedings. Thecourtroom requires a great deal of flexibility. Evidence might bepresented from either counsel table or from a special lectern. Theaudience for any particular piece of information might be the judge,the jury, a witness or opposing counsel. A laptop computer mightgenerate the video signal, or it might emerge from a VCR playing eithera VHS or S-VHS cassette, or from a stand-mounted video document camera.All of these options must be controlled from the judicial bench sincethe judge is the ultimate arbiter of what the jury sees. Courtroomsdemand a high level of display quality. Whether the jury is reading adocument, looking at a diagram or viewing video footage, monitorresolution is critical.
The video scaler can handle all these requirements. It responds tocontrol signals from the judge's bench, routing the video signalwherever the judge decides it should go. Display devices range from15-inch flat-panel LCDs to large-screen presentation monitors andprojectors. The scaler accommodates a wide range of sources anddelivers optimum detail and viewing quality, which is criticallyimportant when a piece of video or a computer-generated diagram orchart might sway the outcome of a trial.
Lecturers need to see the image, too. Video projection use isincreasing in lecture halls, training facilities and classrooms.Because these rooms are expensive to build, they're often designed tohandle a variety of functions, from computer slide shows given by livepresenters to video conferences or distance learning presentations.Multifunction means multiple video and RGB sources. It's muchsimpler, and in the long run more versatile, to connect a scaler'ssingle output to the display device and route all the sources throughthe scaler. In a large facility with long cable runs, it's also cheaperto do it this way.
There's another benefit of using a scaler: While optimizing theimage for the audience, a scaler can deliver a high-resolution image tothe podium. It's not uncommon today to conceal a 15-inch flat-paneldisplay in the podium. In combination with a video scaler, the displaygives the lecturer a brighter, crisper image with a wider viewing anglethan would be available from most laptops. All of those factors willallow the presenter more freedom to engage the audience instead oftrying to decipher a new slide.
Houses of Worship
In larger houses of worship that seat over 800 people in the mainauditorium or sanctuary, it's often necessary to use multipleprojectors to provide a viewable image to the entire congregation. Inthe experience of Shepherd Ministries of Dallas, Texas, which designsand installs multimedia systems for a wide range of religiousorganizations, source material typically comes from VCRs, DVDs,cameras, satellite or cable networks, and computers. These are allconnected to a video scaler, which converts everything to a VGA or XGAcomputer RGB format. The video scaler in turn feeds a distributionamplifier or twisted pair transmitter, which can send multiple copiesof the signal over long cable runs to the different locations in thebuilding where it will be displayed. Without the scaler, thecongregation would be distracted by the change in quality andresolution of the projected images. With the scaler, they focus on themessage, not the medium.
GROWING IN IMPORTANCE
Video scalers are a relatively new type of tool in systemintegrators' kits, but they continue to grow in both usefulness andfunctionality. As video broadcast, transmission and playback sourcescontinue to proliferate and computer displays evolve, video scalershelp the audiovisual system keep pace with innovative developments. Asmanufacturers continue to add functionality to video scalers, they arebecoming more and more capable of being the central control point forboth simple and complex audiovisual systems.
Mike Andrews is the vice president of marketing for Inline Inc.Video scaler application background material was supplied by JimMartin, 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 inanother. For instance, you could connect a VHS player with analogcomposite output, and the video scaler would output the images asdigital component video. Without the scaler, you might not be able topresent archived video effectively on a new large-screen projectionsystem that delivers its best performance with a DVI signal.
A video scaler can enhance signal resolution (once known as linedoubling). An NTSC video signal, for example, is divided into 400horizontal lines, but modern display devices can show two or threetimes that many. Whether you're magnifying an image to auditorium scaleor shrinking it to fit on top of a podium, scalers can interpolate thelines that are missing in the source to enhance the resolution of thesignal. They're not limited to doubling or quadrupling, but performcomplex calculations to convert, say, an older laptop's screenresolution of 800 by 600 to 1024 by 768. A scaler can also downscalehigh-resolution computer signals.
Switching and Control
Scalersgive presenters the ability to choose which sources to display andwhere. Again, these functions used to be performed by separate devicesbut have been incorporated into the video scaler. Some scalers arebeginning to incorporate other functions by enhancing the basicswitching capability.