Desktop Video: Digitize It

by Dave Felder
November 1995

Whether you're a professional videomaker or a weekend hobbyist, your video arsenal may be incomplete if you're not using a personal computer (PC) in your video productions. Your PC can digitize images in glorious color, and even overlay computer generated graphics or titles onto your video footage.

Unfortunately, your computer didn't come with everything you need to perform these tasks--you need to outfit it with the necessary hardware. This hardware includes the digitizer, a device which allows your computer to capture and process video images.

Video Capture Boards
A computer stores all information--be it last year's tax returns or data that describes an image--as numbers. In the case of the latter, you need a video adapter to turn these numbers back into a picture. We use several different kinds of video adapters in desktop video production.

The most popular video adapters found in today's IBM-compatible PCs are SVGA graphics adapters. An SVGA board can reproduce photographically accurate color, known in the computer world as 24-bit color. The SVGA adapter often comes installed when you buy a PC. Macintosh computers come equipped with similar graphics capabilities.

Unfortunately, these boards alone are useless for video production. To use your personal computer for video production, you need a way to input a standard NTSC video signal into the computer and a way to get that video back out to tape.

The most common way to input video into your computer is through the use of a video capture board, often referred to as a digitizer or frame grabber. To go the other way, an "encoder" records the PC's output to videotape. The encoder may be an internal circuit board or an external device.

There are several video capture/encoder boards available that do both tasks. The proper hardware for you depends on your needs, purposes and budget.

Video capture boards come in two major varieties--motion capture and still-frame capture. Motion capture boards have the processing and memory required to digitize a moving stream of video; still-frame capture boards can digitize only a single frame of video at a time. Expect to pay under a thousand dollars for a good quality video capture board capable of digitizing still frames only.

Until quite recently, most motion capture boards in that price range recorded "video in a window" instead of full-screen images. These boards are fine for computer-based multimedia use, but not for good quality video production purposes. Today, full-motion video cards are plummeting in price--see Videomaker's annual Desktop Video Buyer's Guide in the March issue for full details.

The video hardware is half the tools you need. One or more software packages will be necessary for manipulating your images.

The best way to select the proper hardware/software combination is to talk to other video professionals to see what they're using. Find out how easy the software is to learn, how many layers of menus you need to navigate through to perform common operations and how well it suits the unique needs of videomaking. Ask how the publisher supports the software. Is help available through commercial computer services like CompuServe or America OnLine? Does the publisher offer 24-hour telephone support?

Desktop Video Applications
The major uses for still images in video production are image processing (or retouching), graphics keying and titling.

Image processing is one of the most useful capabilities of video graphics boards. Image processing refers to the process of taking an image and electronically retouching it for a variety of needs.

Graphics keying and titling are similar procedures. Both processes allow you to replace portions of your video with computer generated electronic images. In graphics keying, you can add elements to moving video footage. Titling is the superimposing of words onto the screen.

Image Processing
Manipulating still images to create new visuals is one of the most fun (if not devious) things a video digitizer allows you to do. Image processing software lets you combine pieces of several different images into one. It also allows you to change the appearance of your subject.

One project I recently completed for a corporate client needed to show the client's new corporate headquarters. Unfortunately, there was no sign on the front of the building.

The only way to complete the scene was to make a composite image--done by digitizing a photograph of the sign from another facility and pasting it to a second image of the new building. Since the script called for an establishing shot, a still frame worked fine for the scene. Tweaking the photograph in a computer cost much less than any other solution would have.

Another example of a cheap digitizer fix comes from a training video we produced for a medical equipment manufacturer. The script called for a shot of a toggle switch in the "on" position.

However, after viewing a rough cut of the program, the client wanted to show the switch in the "off" position. To avoid the expense of a full day's videotaping, we digitized a still image of the equipment control panel. Next, we digitally cut out the switch, turned it upside down, and pasted it back into position.

Finally, we used a "blend" tool to smooth out the rough edges. In less than half an hour, we completed the entire shot.

But the uses of a digitizer for image processing don't end with the practical. For comedic effect, image processing gives bald people hair and makes hairy people look bald. Want to put a friend's face on Mt. Rushmore or hover a UFO menacingly over someone's house? No problem--you just digitize the necessary images and combine them in the computer.

Genlocking
Earlier we talked about image processing as a way to create composite images. Some video adapter cards can genlock (or synchronize) to incoming video signals, which will allow you to mix the card's output with the video footage. If your capture card supports the genlock feature, you will be able to superimpose computer-generated images over your video footage. Video professionals call this feature keying. A pre-recorded video signal from tape or a live camera signal can be used for keying. If you key over a videotape signal, you may need a time base corrector to get perfect playback.

A common use for keying is to put a graphic over the shoulder of an anchorperson during a news program. In the event you're creating a news or news magazine-style show, here's how it's done.

First you need to create a graphic, usually in a paint package or other graphics manipulation software. This takes a bit of planning, especially in choosing colors and placement of the graphic. The genlock allows you to specify a certain color--the key color--that will become transparent. It's easiest to just set this to your background color, and be careful to not use this shade in your graphic. If you do, the video signal will appear in the middle of your graphic.

If you're keying the graphic over the right shoulder of the news reporter, your computer graphic must be in the upper right corner of the screen. When placing the graphic, keep in mind that the genlock will cut off the outermost edges of your computer screen.

Now, turn on the capture board's genlock function and run your video signal through it. Your output will be a combination of the video footage--which can be coming from tape or directly from your camera--and the computer-generated graphic.

Perhaps the most common use for the genlock feature is to key titles over your footage. The technique is basically the same as in our news anchor example, only you're using text instead of a graphic. And though there's no software specifically designed to create news-style inset boxes, you have many dedicated titling software packages to choose from.

When selecting the typeface for your text, remember that recording out to NTSC will have a definite negative effect on the quality of your graphics (see last month's Desktop Video column for the full scoop). For best results, stick to bold, large letters with lightly saturated colors. Use drop shadows and borders to increase legibility.

Choose the type color to complement the footage you are using. Black letters might look great when keyed over a picture of a sandy beach, but black letters over a night sky wouldn't be legible.

If you watch professional broadcasts, you will notice that many of them use white or yellow letters with black drop shadows. That's because those color combinations work best.

Backgrounds
One area a digitizer can really shine is in creating backgrounds for text. A static blue background is sadly overused in corporate and industrial video. Why so many videomakers default to it is a mystery, especially when the alternatives are so easy to create.

If you open your eyes and look around, you can find hundreds of abstract, interesting visuals that would be perfect backgrounds when you have to put text into your videos. Record them onto tape wherever you see them, and you can digitize them into your computer at a later time.

Or, you can round up various materials and digitize them all at once. Set your camera on a tripod, engage manual focus and manual exposure and play around. Look for items with interesting textures, such as metal, wood and rock. Purposely blurring the focus, especially in close-up, will give a wide variety of useful backgrounds. Experiment with lighting as well--casting light at a low angle across a textured surface will really bring out its depth. Sometimes a "flatter" look makes for a background more conducive to legible text overlays.

Combine those interesting patterns with the capabilities of your personal computer, and you can create an infinite number of backgrounds. With the right software, you can tweak, distort and replicate any texture or surface you digitize.

Here are a few suggestions to get you started:
With your focus slightly soft, grab a freeze frame of the inside of an empty egg carton. Since the egg carton is rectangular, a full shot of half the egg carton will only fill about the top quarter of the screen. Since an egg carton has a strong 3-dimensional look to it, you may want to experiment with your lighting.

Use your software's cut and paste function to copy the egg carton so it fills the entire screen. Experiment using your software's blend or fill tools to soften the edges between the pasted areas.

The end result will be a series of geometric shapes filling up your screen. You would use this image as a background for text.

You could then use a transparency tool to add a colored tint to the picture. You might use a different color background for each section of your video program, or one color for your opening credits and another for your closing.

Another great way to get interesting backgrounds for your titles is to grab a still frame from your video footage and process it. If your video is about your beach vacation, grab a still frame from a wide shot of a beach. Now you can go in and adjust or eliminate the colors, alter the contrast, posterize the image, turn it into small mosaic blocks, combine it with another image...the only limit is your imagination.

Did you ever notice all the colors in an oil slick on water? Try adding a few drops of oil to a tray of water. Move your lights around to get different effects, and digitize the results.

Power Tool
With a digitizer, your PC is a wonderful tool for creating video graphics. It's extremely versatile, able to create just about anything you can dream up. When applied to altering images or overlaying text and graphics, your computer can really set your videos apart from the norm.

David Felder is a writer/producer with Ryan Consulting in Rockaway, NJ.

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