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Edit Points: Linear vs. Nonlinear Editing

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.

Long Live Linear

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.

Linear Lows

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.

Whole New Ballgame

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.

Non-linear Nirvana

With non-linear editing systems, you're no longer a slave to VCRs. That alone makes it an attractive option for anyone who does a lot of editing.

Once you digitize the footage, the computer becomes sort of a virtual VCR. With it you can jump from the beginning of your footage to the end or anywhere in-between with the click of a mouse. You can also get instant feedback on your edit decisions without waiting for prerolls or postrolls.

Don't bother remembering time code numbers or counter numbers in a non-linear system, either. Instead, you store a frame from each video take as a picture-icon or "picon". You can also give each clip a name.

When you want to retrieve a take, glance through the clip library and select the one you want. The computer puts it in the program, which appears on-screen as a timeline in many systems.

Unlike the permanence of linear edits, non-linear edits are completely malleable. You can instantly adjust where and how a scene fits into a show by moving it around the timeline with the mouse. Trimming it ten frames one way or ten seconds in the other is a few finger taps away.

Once you organize the show inside the computer, you need to get it back on videotape so your audience can view it. This is called rendering or mastering, and non-linear systems have different ways to handle this step.

Many systems play back the edited program directly from the digitized video already on the hard disk. In this case the video quality on the master tape depends entirely on codec quality.

Other systems actually digitize the footage twice to give you the most flexible editing, and the cleanest master tape. First, they digitize raw footage at a low resolution to let you cram as much footage as possible on the hard disks for care-free editing. When it's time to create the master tape, the computer redigitizes the scenes at much a higher resolution before it transfers them to the master tape.

How does it do this? By prompting you for the original footage tapes. The process can get as tedious as a regular linear edit session, but the quality of the resulting master tape speaks for itself.

We call the third method "hybrid" editing. With this method, you digitize your footage into the computer at a high compression ratio. After making your edit decisions, the computer transfers each scene from your original master tape to the record VCR. Hence the final product is never actually digitized. This system offers the speed and flexibility of non-linear editing and the uncompromised image quality of analog tape.

Non-linear Lows

You hoped I wouldn't bring these up, right? I'm sad to report that wonderful as it may be, non-linear has drawbacks.

Cost remains the biggest. Although prices on pro systems continue to fall, and manufacturers introduce new models almost monthly that target videomakers like us, non-linear is still beyond many of our budgets.

The dedicated hardware and software don't cost much. The computers and hard drives do, however; from two to five times more than the nonlinear gear.

Don't forget about monitors, of which you'll probably need two. Anyone who works with non-linear will recommend not only two monitors, but two big monitors to make the work really glide. Again the price goes up.

When the register finally rings, the average price for a basic non-linear package comes in between $5,000 and $10,000. For stand-alone systems that approach broadcast quality, expect to spend twice that much or more.

If you knew a particular system would last a long time, and still have support years down the road, you might find it easier to justify the high cost of non-linear. Unfortunately, you don't have that promise yet.

As computer technology pushes forward, so will non-linear. Count on big gains in digital video storage and compression, as well as lower prices on computers and hard disks in the very near future.

What does that mean for you? It means a state-of-the-art edit system you buy today may be worth less than a closet full of BetaMax cassettes a year or two later.

That dependence on cutting-edge technology can also breed problems like system "crashes" because manufacturers haven't worked out the bugs. Anyone familiar with non-linear will talk of glitches appearing now and then on even the most dependable edit systems. Depending on when they hit, those glitches might force you to remake the last edit or rebuild the entire show.

Making the Choice

You may read the list of linear pros and cons and crown non-linear king. I'd probably agree.

But keep this in mind--on certain types of productions, a traditional linear system may actually be more efficient. On other types of videos, where flexibility and easy revision are important, non-linear reigns supreme.

If you decide to take the non-linear leap, do your homework. Try out as many different systems as you can, and read about the ones you can't try "hands-on." Make sure you can afford enough disk space to make a system functional. Nothing would cripple you more than a non-linear system with only ten or fifteen minutes of storage.

Also, understand that the system you choose may indeed be obsolete in five years. Remember the 386 PCs and one-box Mac computers that were all the rage a few years ago? These systems may share the same fate.

An alternative to a true non-linear system is the hybrid editing system that lets you work in either traditional linear or non-linear mode. These unique systems can control VCRs using standard interfaces, or operate as a fully digital non-linear system.

They make great edit controllers for VCRs because the computer's power helps you get the most from the editing process. Should you get a project where non-linear would make things easier, they can do that, too.

What if your work will never end up on videotape, but instead on a computer hard drive or CD-ROM? Non-linear is certainly the best option. Find a system that records video and audio files supported by your distribution format. Many non-linear software packages can export either Microsoft's Video for Windows or Apple's QuickTime formats.

Whatever you do, make sure to keep your eyes and ears tuned to the new developments in non-linear technology. If you have the budget to step into non-linear right now, you'll be on the leading edge of some exciting technology. For those of you on tight budgets, system prices are coming into your range in a hurry. And when they arrive, you won't want to miss the chance to join the future of video editing.

Tags:  November 1995
Mike
Loehr
Wed, 11/01/1995 - 12:00am