Large video presentations have become simpler recently, thanks to the rapid evolution of rgb tools.


RGB Spectrum’s SynchroMaster 450, a synchronous switcher with internal video scalers, is designed to handle large-scale staging events like this one.

Industry professionals have no doubt followed the growth of the RGB seamless switcher market in recent years. Indeed, such devices — designed to mix and switch seamlessly between disparate sources of interlaced and progressive-scan video — are all the rage for large-group presentations these days.

In fact, they work so well that newer, smaller versions are now hitting the market. These compact switcher/mixers are intended for small conference rooms, classrooms, and auditoriums. Even the fancier, full-featured units, designed for conventional staging, are now adopting such exotic technologies as IP addressing and LANs.

Ironically, as corporate and educational presentations become more complex, they have also become simpler, thanks to this new technology. RGB seamless switcher products have basically made it possible for any producer to ignore the source format of the electronic images used in large-screen presentation. Instead, the process has become “plug-and-play” — simply connect all the different sources, select the desired output resolution and image refresh rate, and off you go.

If these products really are so powerful and easy to use, why weren't they developed much earlier? For the answer to that question, and some insight into how an RGB scaler/switcher works, let's lift the cover off the box and do some nosing around.

Square Pegs, Round Holes

While the process of mixing different video and RGB signals might seem no more complicated than mixing audio to a layperson, there are plenty of Rube Goldberg-like machinations involved.

For starters, the current analog (and digital) NTSC system used in the U.S. employs interlaced video exclusively. That video can travel in three flavors: either down a single wire as a composite signal (with luminance, chrominance, and sync all mixed together), down two wires as Y-C (luminance and chrominance separated), or down three wires as YCbCr (luminance and two color difference signals). But all three systems are still interlaced.


Folsom’s BlendPro, a tool for combining up to four video or RGB sources into a widescreen image, demonstrates its capabilities with Space Shuttle images at Infocomm 2002.

By contrast, desktop and notebook computers send a four- or five-wire signal to the associated computer display monitor. In the four-wire system, those signals are red (R), green (G), and blue (B), plus composite sync (Cs). In a five-wire system, the composite sync is broken into separate horizontal (H) and vertical (V) sync pulses.

Note that, except for rare exceptions, all RGB displays employ progressive-scan video. So right off the bat, there is not only a mismatch in the number of cables between video and RGB, but also two different ways of scanning the image. Things get a little more compatible with DTV signals, but not much. 480i DTV remains interlaced, as does 1080i. Both use a three-wire system with luminance and two color difference channels, with color spaces identified as YPbPr. 480p and 720p signals are at least progressive-scan formats, but they also employ the YPbPr scheme.

Some set-top DTV receivers output all ATSC formats as RGBS or RGBHV. However, if the electronic display does not support the tri-level sync standard of ATSC signals — and many computer monitors do not — they will be unable to stay locked up on the image for very long.

In short, a mish-mash of cables, sync, and scan formats are operating in today's boardrooms, not to mention backstage. And now, we want to mix them seamlessly?

Mathematical Juggling

Until recently, it wasn't practical to develop a “black box” that could easily translate from one of these formats to another. For one thing, any mixing would have to be done in the progressive-scan domain to match the optimum image quality requirements of large-screen displays. For another, it would take top-notch decoding of video sources to prevent dot crawl and color moiré in the final images.

Thanks to free-falling costs of developing and producing ASICs (Application Specific Integrated Circuits), it became possible to manufacture circuits to convert interlaced video to progressive-scan video in the early 1990s. These line doublers, as they were called, were first developed by Faroudja Labs. They turned any composite or component video source into a VGA computer signal.

Subsequent developments by Faroudja and Snell & Wilcox resulted in devices that could quadruple the number of scan lines in the converted images by interpolating new picture scan lines from existing ones — in effect, inventing new picture elements that never existed. These line quadruplers doubled the vertical resolution of the image, creating a need for electronic displays with more available pixels.

Over time, manufacturers of front LCD and DLP projectors kindly obliged. But a funny thing happened on the way to the screening room. Someone asked, “Why not convert video signals to match the display resolution precisely?” Thus was born the native-rate scaler, which lies at the heart of any seamless switcher/mixer product.

Instead of simply de-interlacing the video fields and presenting them progressively, or quadrupling the scan lines, native-rate scalers converted video sources to a specific RGB output resolution not tied to any video standard, like SVGA (800×600 pixels) or XGA (1024×768 pixels).

Good thing, too, as the electronic display market in the latter part of the 1990s slowly shifted away from raster-based imaging with cathode-ray tubes, and moved instead to flat-matrix panels with fixed-pixel arrays, such as LCDs, DMDs, plasma, and the D-ILA reflective LCD panel. (Some of these imaging systems have pretty oddball pixel resolutions, like 848×600, 852×480, 1024×1024, 1365×768, and 1365×1024 pixels.)

Slicing and Dicing

The stage was therefore set for a product that could accept a wide range of input signals and cable formats and output them to match any of the flat-matrix imaging systems described. Thus, the RGB seamless switcher was born — first seen in a staging and rental package as Folsom Research's Variable Format Converter and Analog Way's Graphic Switcher.


Front and back view of Kramer Electronics’ VP-723DS, a IRU seamless switcher/scaler.

Those two companies have since been joined by a host of other players in offering variations on these wonder boxes — Extron, FSR, RGB Spectrum, Altinex, Communications Specialities, Inline, and Kramer Electronics, to name a few. While individual designs vary, most of these seamless switchers provide five to eight inputs (which can be any format at all, from composite NTSC to 1280×1024 SXGA RGB, and even 480p/720p HDTV) and offer one, two, or three upconverted outputs at any standard RGB pixel resolution.

Internally, all interlaced sources are decoded (composite) and then converted from the YUV color space to RGB. Additional circuitry provides motion compensation, noise reduction, and 3:2 pulldown correction for interlaced video sources. In this manner, 480i video becomes RGB 480p video with progressive scan.

The next step is to scale — or resize — the 480p material to the desired output resolution, such as 1024×768 pixels. Other RGB sources that are already progressive are also similarly up-converted or down-converted using digital scaling techniques that interpolate additional pixels (scaling up) or compress and decimate pixels (scaling down).

Finally, the up-converted sources are mixed or switched from one buffer to another. Note that all mixing, dissolve, wipe, and iris effects are done at the final output resolution, which requires quite a bit of RAM to pull off. Sync correction and genlock are also introduced here so that the final image sent for display has no “hits” or glitches.

But Wait, There's More

The beauty of these devices is that all switching and mixing/effects functions (even title supers) are similar to those used by standard production video switchers and character generators. It was a simple matter to bring out a production switcher interface for these products and give the operator a familiar environment — a big help backstage during a complicated show.

The first iteration of such an interface was seen a few years back in Folsom's booth at InfoComm. Clark Williams of Vista Controls in Arizona had developed a full production switcher with program and preview buses, plus the familiar T-bar for “taking” a given transition. Since then, his creations have grown in size, and the latest version incorporates IP connectivity for operation over a LAN. (Virtual switching, anyone?)

Analog Way was the first to introduce a rack-mount scaler/mixer with preview and program bus arrays, plus a built-in T-bar. This product, known as the Graphic Switcher, really helped the staging and rental market take off. In short order, Folsom introduced its own rack-mount design (Screen Pro), as did Extron (SGS 408, with two different switcher interfaces) and FSR (Omni Navigator).

Who's Got What

If you are seeking a scaler/mixer solution, here's a sampling of some current products:


Folsom’s Screen Pro Plus 1600 controller.

Folsom Research has come a long way from its original VFC design. Now, Folsom offers a variety of seamless switchers for everything from staging to systems integration. The Screen Pro Plus 1600 breaks new ground by incorporating all I/O connections and switching/sync/blending functions into a standard switcher design. It can control up to six screens (depending on model) and features 16 universal inputs (everything from NTSC to 1600×1200 UXGA and HD sources can be connected), one or two PiPs per program, 64 presets, and T-bar control.

Widescreen presentations are possible when using the BlendPro. It lets you mix up to four video or RGB sources and create a widescreen, seamless panorama with tiled video/RGB overlays. The extent of featured-edge overlap on each screen is user-programmable. Systems integrators can add seamless switching with the full-featured Presentation Master, an eight-input/dual-output seamless switcher with stereo audio follow. Thirty different user-programmable output resolutions and Auto Signal Lock on all inputs are standard.

For smaller installations, Presentation Pro is a viable alternative. It has a 2 RU design that provides seven universal inputs, user-selectable output formats from VGA to SXGA and HDTV rates, plus a wide range of seamless cuts, dissolves, wipes, and fade effects. Dual buffered video outputs and stereo audio follow are standard.

Analog Way invented the “classic” seamless switcher, as well as the name. Its current offering is the Graphic Switcher II, which provides eight inputs for RGB or component video sources (including DTV), and eight additional inputs for composite (or configured for four Y/C signals). There are two outputs (one main and one preview) that support resolutions from VGA to SXGA, HDTV, and the 1365×1024 4×3 SXGA standard. It's possible to create widescreen shows with feathered edge-blending by combining two or more Graphic Switcher II models.

AW's Octo-Plus OCP802 scaler and switcher is a system that addresses the installation seamless switcher market. This 2 RU design offers eight universal A/V inputs for interlaced and progressive-scan sources up to 1600×1200, and provides two buffered outputs at resolutions up to SXGA (both 1280×1024 and 1365×1024). Stereo audio inputs are switched and follow each output selection.

Extron Electronics has a number of choices, including the SGS 408. This has a “classic” seamless switcher design, with eight inputs and two outputs (preview and program). Two different switcher consoles are available as options — one with conventional push-button switching, and one with a T-bar for dissolves and wipes. Pre-programmed effects, such as fade, wipe, and dissolve, can be adjusted for timing and saved to memory, and output resolutions to 1280×1024 are standard. (Extron also offers a Vista Controls console for the SGS series.)

The ISS 108 and ISS 408 integration seamless switchers both offer eight inputs (any interlaced or progressive source), dual buffered outputs on 15-pin jacks and BNCs, and a preview output. The ISS 108 supports 17 different output rates to 1024×768, while the ISS 408 adds HDTV compatibility and will scale up to 1365×1024, as well as 480p, 720p, 1080p, and 1080i. Both incorporate automatic 3:2 pulldown detection, audio cross-fading, and feature five test patterns for display setup.

FSR's Omni Navigator is another “classic” design seamless switcher. It offers eight inputs, dual program outputs, one preview output, test/background key, and picture-in-picture. It accepts interlaced and component signals up to UXGA (1600×1200 pixels) and outputs at RGB formats up to XGA (1280×1024).

FSR's Compass is a 1 RU systems integration design with seven inputs and one output (no preview bus). It uses programmable effects and accepts everything from composite to 480p and 720p HDTV, and up to 1600×1200 RGB sources. The unit's maximum output resolution is 1365×1024, and 50in. plasma resolutions (1280×768 and 1365×768) are supported.

Kramer Electronics recently announced a pair of versatile 1 RU seamless switcher scalers. The VP-723DS will accept composite, S-video, component, and DVI sources, as well as RGB, and converts to a wide range of RGB rates from VGA (640×480) to UXGA (1600×1200). In addition, there are five non-standard output rates for plasma, LCD, and D-ILA devices, plus 480p, 720p, and 1080i DTV formats. Kramer's VP-720DS is slightly less expensive and has all the above features, but doesn't support DTV output rates.


Extron’s SGS 408, featuring a seamless switcher design, with eight inputs and two outputs.

RGB Spectrum is also a seamless “player” with its SynchroMaster 450, a full-featured seamless switcher/scaler with four RGB inputs (VGA to SXGA), eight optional video inputs (composite and component), a preview output, and scaling at any output rate up to SXGA (1280×1024). A PanelLink DVI output option is available. The SynchroMaster 450 can be operated as a stand-alone unit or as a 2 RU permanent installation.

Vista Controls has souped up its line of after-market seamless switcher controllers. Vista's ScreenMaster II-1608 features a 15in. color AM LCD screen for setting sizes and effects, 32 user-definable Quick Keys, 112 presets, and integrates with the CanvasMaster seamless widescreen server. Up to 16 input sources and eight program destinations are offered, and the SM II-1608 interfaces with Folsom and Extron seamless switchers, as well as Pesa, Extron, and Sierra video switchers.

Need more I/Os? Vista's ScreenMaster III-3216 brings 32 inputs and control of up to 16 program destinations to the table, plus a pair of 15in. color AM LCD screens, unlimited preset definitions, user-definable Quick Keys, and LAN control from CanvasMaster. The latter product allows the creation of presentations in PowerPoint with a user-defined aspect ratio — presentations which are then published to CanvasMaster. PiP windows and border and shadow effects are easy to integrate into the final widescreen presentation.

Non-Seamless Video Scalers

Altinex has designed the MT106-102 plug-in scaler card for use with its unique MultiTasker system. This card accepts NTSC or PAL composite video, S-Video, analog computer video (VGA-UXGA), and digital computer video (DVI) signals from VGA to UXGA resolution. The output is analog through a 15-pin d-sub jack from 640×480 to 1600×1200, and several non-standard resolutions for plasma and LCD monitors and 4×3 SXGA (1365×1024) are included.


Communications Specialties manufacturers four different flavors of its Deuce rackmount/tabletop scaler.

Communications Specialties manufactures several “Deuce” rackmount/tabletop scalers, starting with the Deuce SDQ-2240. It is a combo scaler, doubler, and quadrupler with five output resolutions from 800x600 to 1280×1024. The Deuce HD2230 offers five scaled outputs, including three DTV rates, SXGA, and Wide XGA (1365×768), while the Deuce MC-2220 offers full control over six motion compensation settings and provides a mix of 4×3 and 16×9 outputs. Finally, the Deuce Pro 2210 supports a multitude of 4×3 and 16×9 input and output aspect ratios and scan rates, and provide full control over all video signal parameters.

Inline offers the IN1408, a stand-alone box (also rack mountable) that lets you switch effortlessly among up to eight different interlaced video sources and four RGB sources (maximum eight inputs at any time). In addition, inputs five and six support DVI. Output signals are scaled from 640×480 to 1600×1200, and there's also a DVI output.

Yet to Come

If there was ever a product category that could be labeled “set it and forget it,” seamless switching is it. In fact, the idea of seamless switching appeals to anyone who has had to make a mixed-media presentation. The only thing better than having one of these boxes at your fingertips would be to build it right into an electronic display. Won't happen anytime soon, right?

Well, actually, the elusive goal of integrating these functions of decoding video, scaling video, and mixing video into a electronic display was attained this past NAB, when Barco showed the IQ G300 installation projector.

This unique design also allows tiling of up to four video/RGB sources, in addition to seamless transitions between sources.


Analog Way’s latest offering: the Graphic Switcher II.

Other manufacturers are already providing card slots for development of after-market seamless switcher and scaler products. Notable examples of this trend include Pioneer's new 50in. and 43in. FlexPlasma monitors, and Sanyo's large-venue LCD projectors. Look for more projector and monitor manufacturers to jump on the seamless bandwagon by InfoComm 2003.


Pete Putman, president of Roam Consulting Inc. in Doylestown, Pa., and author of “The Toastmasters Guide to Audiovisual Presentations,” regularly reviews large screen displays and computer/video interfaces. He also serves as senior contributing editor for SRO's sister publications, Video Systems and Sound and Video Contractor. The Roam website can be found at www.projectorexpert.com.