BARCO Tech Tip: Switch Hitter - AvNetwork.com

BARCO Tech Tip: Switch Hitter

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During a recent meeting with a new client, I introduced our product line to the heads of their video department. While taking them through our seamless switcher product line, one of the team members expressed the lack of "quick switching" as the reason for not using that type of product in their workflow. Their typical show solution was to sub-switch graphic sources "upstream" of a basic video production switcher.

While sub-switching is effective, there's a new generation of production switchers on the market that directly target this type of client or event. This "next-gen" switcher combines a traditional video production switcher with the scaling abilities of a seamless switcher. As this new type of switcher starts to appear on the scene next year, knowing the differences between traditional and seamless switchers will be an invaluable asset to your ability to evaluate them properly.

Advantages and Limitations
Video production switchers have been an essential tool in event and broadcast systems for the last... well since AV was invented. These switchers operate in the 4:2:2 color space, meaning that they output standard or high definition SMPTE resolutions such as 480i (NTSC), 720p, 1080i or 1080p. These devices include a complex internal crosspoint matrix that requires all video signals within the matrix operate at the same resolution. The "mono-resolution" processing allows the user to perform quick, glitch-free cuts and other tricks such as advanced layering and re-entry. The limitation, however, is the switcher's inflexibility in the types of inputs that it accepts. Because of this, a complete engineering package for a production switcher typically includes some quantity of video converters, which make it possible to bring "non-native" sources into the crosspoint matrix.

Scalers at Heart
Seamless switchers differ from video production switchers in that they are not generally limited to SPMTE resolutions. In fact, unlike production switchers, seamless switchers are designed to switch sources for progressive display devices, such as projectors or flat panel monitors. In addition, seamless switchers operate in a 4:4:4 color space, which allows for full, un-compressed processing of graphic signals.

At the heart of a seamless switcher lies at least one, and in many cases multiple, signal scalers. These scalers enable the seamless switcher to accept virtually any input type, and convert the signals to a common output resolution. While this provides more flexibility than a traditional production switcher, the source-to-source conversion process can take as much as one second, and this, in turn, limits quick switching. The scaling process also puts limitations on some advanced keying effects.

Best of Both Worlds
In the marketplace, the new breed of switchers uses a traditional production switcher as a foundation, but adds in the ability to perform on-board scaling. This combination of talents makes them extremely useful for single screen productions that include a mix of graphic, computer and "native" sources such as cameras. Some "new breed" switchers utilize onboard scalers within the internal signal flow, while others utilize input cards that convert signals to match a common resolution at which the switcher is set.

In both cases, as you begin to evaluate these switchers for your workflow, it's important to compare the following criteria:

  • Latency and delay: how much time does it take for video signals to flow through the switcher?
  • Input flexibility: are there limitations to the types of signal resolutions that the switcher can input?
  • Output flexibility: are there limitations to the types of signal resolutions that the switcher can output?
  • Scalers: How many on-board scalers are available to convert signals? The more scalers, the fewer restrictions you'll have during your production.


These key factors are directly proportional to how much flexibility you'll have when using the system during your events. The results of your evaluation will also indicate the amount of outboard gear you'll need to make the system work for you, whether the event is simple or complex.

The overriding goal is to achieve a balance between the two worlds -- the input and output signal flexibility of a seamless switcher, and the production switcher's quick switching and ease of use. As with any new technology, there are a number of competing solutions, and as we approach next year's trade show season, we'll soon see which ones clearly work for the Rental and Staging marketplace, and which ones fall to the side.

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