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Edit Suite: Switcher Magic

Edit Suite: Switcher Magic

Once upon a time you could make a decent living producing clean, cuts-only video productions. Those days are gone. The viewing public, inundated by high-end, computer-generated video effects in TV shows, feature films, industrial videos, trade-show displays and even wedding videos, now expects sophisticated dissolves, wipes and bounces.

To produce such special effects, you need a piece of equipment known as a switcher.

The Black Box

A video switcher is one of those magical black boxes that allows you to incorporate titles and special effects into your productions. Here's how it works: you feed video into the box, and then you work wonders on the video before it exits the box. These wonders run the gamut from a simple switching of signals to the complex creation of a video cube.

Some of you low-budget producers out there may ask, why invest in a switcher? Why not incorporate effects as you shoot? True, some camcorders sport an impressive array of video signal manipulators that you can use on location. But if you apply a strobe effect to a scene while shooting, you can never remove it later. Save the making of your special effects for post production, and you can change your mind a hundred times. Thus the need for a post-production switcher.

There are two types of switchers: distribution and production switchers. Let's begin with the former.

A distribution switcher is a routing device for video signals. What it does is take many nonsynchronous video sources and route them to different destinations.

Say you have three VCRs at home, each one playing a different movie. On VCR One, you play Gone With the Wind. VCR Two features Friday the 13th. Rambo rolls on VCR Three. You could hook the video output from all three VCRs to a routing switcher. A video out from the switcher feeds to the large screen monitor you're watching. By pushing buttons on the routing switcher, you can alternate which VCR signal you wish to view. Keep in mind that many routing switchers are nonsynchronous. Which means that when the signal changes from VCR to VCR, the crucial sync signal is broken and stability suffers. The picture may roll or break-up as the view changes from Rambo to Rhett. This is a glitch.

On the other hand, you've got production switchers, which you use in the actual process of video production. There are many differences between a production switcher and a distribution switcher; but one inequity is fundamental. With a production switcher, your picture remains stable throughout the switch. You'll see no break-up, rolls or glitches--except what was already there. When you switch from Sylvester Stallone to screaming teens, there's a clean cut from source to source.

How does this miracle of miracles happen? Synchronized video sources, that's how. The key is a genlock system (in the case of cameras) or a TBC (in the case of tape playback); both make one video signal run in time with another. Most of today's consumer-level production switchers incorporate frame synchronizers at their inputs, which eliminate genlocks and TBCs. Then the production switcher itself makes sure all the video signals run through it at the right time so they can mix with each other without mishap.

Operating a Switcher

Switching is not as easy as it sounds. I remember the first live telecast of my college days.

"Mark," my Teleproductions instructor shouted, "you're on the switcher for tonight's broadcast."

No problem. Just push a couple of buttons...it'll be a piece of cake. Or so I thought.

To make a long story short: the viewers sat through about two minutes of solid black and color bars and I was back to cable jockeying for a while. Fortunately, you won't cut your video teeth on a live broadcast. You have the advantage of making your mistakes on tape.

When running a switcher, your main concern is keeping track of what's coming in and what's going out. Every video signal fed into a switcher is assigned a button. These buttons fall in rows across the switcher; each row is a bus. Usually you'll find three types of busses on a production switcher: 1) the program bus; 2) the preview bus; and 3) the mix/effects bus.

When you must decide which video source or combination of sources will go out to the recording deck, you choose the program bus. Pressing a button on the program bus that represents a particular video signal makes that signal the switcher's output. Whatever you choose in the program bus records on tape.

The preview bus is for us experimenters. The output from the preview bus connects to a preview monitor. You can see the source of the video, or try out an effect before it actually goes out on line. This is extremely helpful in live situations, where mistakes can be embarrassing. It's also handy in the post environment, when you don't want to waste time and tape by continually recording an effect until you get it just right. The preview bus works independently of the program and mix/effect busses.

You create special effects such as fades, wipes and superimpositions through the mix/effects bus. All that fancy stuff you're dying to do you'll do with these buttons.

Most consumer and semi-pro switchers usually have one program bus, one preview bus and one mix/effects bus. High-end models may have three or four pairs of busses assigned to each of the different switcher functions. Though similar in operation, the output possibilities are endless.

Let's Get Switching

You know what a switcher is. You know how it works. But how can it help your productions?

Switchers typically perform four types of transitions: fades, cuts, dissolves and wipes. The cut is the simplest effect a switcher performs. It acts like an edit, only the transition is live on tape instead of a manual manipulation.

Say you shot your last wedding gig with two cameras. Camera A was a head-and-shoulders shot of the bride and groom from behind the altar. Camera B, perched in the balcony, recorded reaction and establishing shots.

As you now edit the nuptial production, you run both tapes in sync through a switcher. As the couple turns to face the congregation after their kiss, you decide to cut to a wide shot. Without a switcher and two decks running simultaneously, you'd do this by swapping tapes and trying to match movements for an invisible manual edit cut.

But with the switcher, it's much easier. With Camera A on line (recording to the program deck), you simply depress the Camera B bus at the time of the cut. Simple. Any time you want to cut from one source to another, you just depress the proper button.

Superimpositions, dissolves, fades and wipes are more complex. At the beginning of the marital memory, you decide to slowly fade up from black. Select the black background color in the A bus. Select the wedding video source in the B bus. Make sure the fader bar is in the A bus position. When you're ready to execute the effect, press the mix button (or select the dissolve effect) and slowly move the fader bar from the A to B bus position.

Many switchers have auto fade controls. You can set these controls with timers to vary the speed of the fade. The auto fade also insures a steady, continual rate of fade often not duplicated by the human hand.

You can dissolve between video sources in the same way. Instead of choosing black in one of the busses, simply select another video source. With the fader bar engaged, the signal slowly fades from one image to another. Superimposition occurs when the fader bar stops halfway between the busses. You can view both images in varying intensity, depending on which bus the fader bar is closer to.

Wipes are very popular switching effects. During this process, one video source "wipes" another off the screen. Set up and executed in much the same way as a dissolve, the wipe is a more noticeable transition.

One of the most common uses of the wipe function: the split screen effect. When the fader bar is midway between two busses, the images do not superimpose over one another as with a dissolve. Instead, half of each video image appears on the screen--either horizontally or vertically. Even low-end switchers typically boast a variety of wipe patterns. These range from simple circle and squares to complex Venetian shade effects. You can control the speed of the wipe as well as its edge definition. A hard-edged wipe displays the source image moving across the screen as clean and crisp. Soft-edged wipes distort the edge of the image, softening it.

With many of the shaped-wipe patterns, a joystick controller allows you to position the starting point of the effect. Let's say during that wedding video you want a shot of the bride's mother to "heart wipe" out from a shot of the couple kissing. The joystick allows you total creative control; you can even position the effect so that it starts from the couple's lips.

Switch On

In today's high tech world, switchers boast many more options than the basics described here. The most sophisticated--and expensive--switchers have built-in Digital Video Effects (DVE) machines. DVE machines create custom transitions, such as the bouncing screens and titles mentioned at the start of this column. Not all effects are available on all switchers and, as you might imagine, cost generally rises with the quality of effects.

Super snazzy effects aside, the switcher's most vital function remains flawlessly switching from one video source to another. Don't get boondoggled by a piece of gear just because it can turn your video into a boat and sail it off the screen. If it can't make a clean switch between signals, it's not worth it.

Nothing annoys viewers more than a video that spits and sputters between every cut and transition. Mistakes like take the wind out of any production.

With a switcher, you can count on smooth sailing.

Videomaker contributing editor Mark Steven Bosko is the vice president of marketing for a commercial production company.

Tags:  November 1994
Mark
Bosko
Tue, 11/01/1994 - 12:00am