Edit Points: Linear vs. Nonlinear Editing

Have you heard the buzz about non-linear editing? You know, the computer systems that let you cut and paste video together the same way you cut and paste sentences or paragraphs in a word processor? Curious about what these new systems can and can't do? You should be.

Without a doubt, the future of video lies in computer technology and non-linear editing. Unlike the VCRs and controllers you may use today, computers make the editing process simple and incredibly flexible. If you plan to edit on into the future, and you want to have fun doing it, you'd better turn an ear toward the non-linear buzz.

When I say non-linear is the future, I don't mean linear editing is dead. Quite the opposite. We've built up programs on videotape for nearly thirty years using linear tools and techniques. It's safe to say we'll continue doing so for at least another five to ten.

Longevity is linear editing's great asset. You can find plenty of linear editing tools in the marketplace, along with books, magazines and videos to help you get the most from them. You'll also find folks familiar with linear editing who share your enthusiasm and can offer tips to improve your work.

I can't say the same for non-linear yet, as the technology remains fairly young. Those daring enough to try it often learn their system alone, and at the mercy of sometimes finicky hardware or software. They also pay a hefty price for their toys.

Getting into linear editing, however, doesn't cost much. For less than $1,000 you can get a complete edit system that will give you the basics. It won't be the most efficient or flexible, but it will edit.

Editing your projects with a linear system may take some time, but it's only a one-step process. Once you make the last edit, you can immediately sit the audience down and let them watch the show. As you'll learn in a moment, non-linear adds a step before you can edit, and another before the audience can watch the finished show.

Most linear edit systems work fine, but they make you play the editing game according to some annoying rules. The most unsettling: everything happens on videotape.

To get from one place to another on a tape you have to shuttle past everything in-between. One could argue that you spend more time waiting for tapes to cue with a linear system than you do making edits.

Linear editors also aren't very flexible. You can't easily build a program out of sequence or in separate "chunks" using a linear edit system.

For example, say you'd like to build the middle of a show first, and then add the beginning and the end later. With a linear system, you can create segments on separate tapes and then dub each one onto a master tape at the appropriate time.

In the process, however, you lose a generation. With many consumer formats, you can't afford to give away a generation of video quality unless you have no other choice. With linear, you don't.

Should you decide you want to change part of a program after you finish editing, a linear system hinders you more than it helps.

The only way to change a previously made edit is to perform a new edit "on top of" the old one. If the scene you want to add happens to run longer than the scene you're replacing, you'll cover up a bit of the next scene on the tape. If it's shorter, you'll have a bit of the old shot still in the program.

What's the solution? Either make the new edit fit, or rebuild the show from that edit to the end. Neither of these options is very pleasant.

Non-linear editing completely changes the rules, and it changes them in your favor. Instead of building a program in sequence one shot at a time, non-linear systems let you work on any part of a program at any time. Changes that may take hours or even days on a linear system may take nothing more than a few mouse clicks with non-linear. Where linear editing makes you wait for tapes to cue up, non-linear gives you instant access to whatever clip you want, whenever you want it.How do they make this editing magic possible? By transferring the video from raw footage tapes onto hard disks inside a computer. Once inside the computer, the possibilities for manipulating the video literally become endless.

Many non-linear software packages let you transform digital video using effects identical to many broadcast linear systems. You can perform effects like dissolves, multiple layers, squeezes, glass breaks--you name it. A few can also integrate features of image design programs like Adobe Photoshop and Fractal Design Painter, something linear systems will never do.

Video Digitizers

Of course none of this happens without first getting the video into the computer. That's where video digitizers come in.

Video digitizers live inside every non-linear system and do essentially the same thing: convert motion video into data files storable on hard disks.

A stream of raw digital video is huge, requiring many megabytes of storage for each second of uncompressed video. At that rate, you can't store much raw digital video on anything less than a mainframe computer. The seemingly large 1 gigabyte drives found in many multimedia computers will only hold a few minutes of video footage.

To make digital video manageable on personal computers, digitizers use codecs to compress the data before they store it and decompress it upon playback. (Codec comes from "COmpress-DECompress").

Codecs go by nifty acronyms like MPEG, Indeo, Motion-JPEG and Wavelet. I could write an entire article about how codecs work, but all you need to know is that they do. Some look better than others, and your eyes will quickly tell the difference.

We call the best codecs lossless because they reduce the size of digital video data without making a noticeable impact on picture quality. While they make pretty pictures, lossless codecs aren't able to reduce the amount of data much. That's because they can only scrunch digital video so far before the image suffers. Lossless codecs typically "max out" when files reach 20 to 30 percent of their original size.

"Lossy" codecs generate significantly smaller data files, but at the expense of picture quality. They reduce image detail to make the digital video file smaller. Lossy codecs can shrink files to as little as 1/100th of their uncompressed size.

What happens to the image when you compress and decompress it? That depends on the codec. Typically, the lower the compression ratio, the cleaner the decompressed video will look.

Some high-compression codecs leave artifacts in the video; these may be odd-shaped clumps of pixels that appear randomly across the screen. These artifacts represent areas where the codec sacrificed detail to reduce file size.

The newest codecs can scrunch files to 1/50th of their uncompressed size and retain image quality slightly better than standard VHS.