Desktop Video: Digital Nonlinear Editing

In the film Hearts of Darkness, Francis Ford Coppola made a telling remark on the future of motion pictures. He said that the next great film may well come from a young girl shooting with her father's camera.

If someone asked him today, he might add that she'll probably edit it on her family's DTV computer.

There's no doubt that DTV post-production is impressive. Once you have digitized your video, you can store it on the hard disk and access any part of it in seconds. Using tape, you spend more time on fast forward and rewind than you do editing. With random access nonlinear, you can jump to a video or audio clip at any point on the disk and keep playing without missing a frame. Add to that the ability to make countless copies without any generation loss, and you can see why some people say tape is dead.

In this piece, we'll look at the pros and cons of digital nonlinear editing. We'll tell you who makes the software and hardware, how it works, and whether or not you're likely to be trading in your VCR for a hard disk.

One catch: you may not fit much video on that hard disk. When digitized, video data is huge. A single frame takes up nearly one megabyte of storage; in just a few seconds, an uncompressed video stream would fill a one- hundred meg hard disk.

Lucky for us, the new technology of compression and decompression (codec for short) allows you to squeeze more video into a smaller space. But codecs do this at a cost to image quality. When using the popular Motion JPEG codec, video images begin to suffer at a compression ratio of 10:1 (which discards a whopping 90% of the video data). At 20:1, digital compression artifacts become obvious.

Before using a codec, we could store just a few seconds of video on a hundred meg drive. At 20:1, that puts us close to a minute on the same drive. At an average storage cost of $100 for that minute, you can see why digital video has failed to make tape obsolete. At ten cents or so for one minute of high-quality Hi8 or S-VHS tape, there is simply no comparison.

This is changing very rapidly. Costs of hard disk storage are dropping faster than 50% per year, and the speed and power of computers continues to double about every 18 months. So it's likely that you will be able to at least play with nonlinear editing sometime soon.

If you start with software like Adobe Premiere or Avid Videoshop on the Macintosh, or perhaps Premiere for Windows on the PC, you can gain experience with nonlinear timeline-based video and sound editing. (For more on this, see the March 1994 issue). The entry cost is just a few hundred to a thousand dollars or so, and most everything you learn will transfer to any of the integrated nonlinear systems. These, by the way, can cost up to $90,000 (for Avid's industry-leading Media Composer).

To begin nonlinear editing, you'll need some way to digitize your video and audio clips.

On the PC, you could try to locate someone with an Intel Smart Video Recorder Pro (or the Creative Labs Video Blaster RT300). These cards, which cost about $500, will make files you can take to any PC for editing, since they don't need the capture card and its codec to play back.

These products use the new Indeo codec from Intel. This is a consumer codec that uses hardware for compression but software only for decompression; that's why it's called a "hardware-software" codec. Indeo can play back without special hardware on the fast new Pentiums and PowerMacs (there is no Indeo capture card for the Mac as yet). If you buy your own Indeo card, you can offer friends a digitizing service.

The Motion-JPEG codecs found in other video capture cards need hardware to compress and decompress. The same goes for MPEG, used for Video CD-ROMs and compressed direct broadcast satellite video. They are "hardware-hardware" codecs.

A Motion-JPEG card creates a file that, in theory, can play back on other M-JPEG cards. But in practice we've found very few cards that can read each other's files. In a recent study, only the Miro DC1 TV card played back another card's file (Videologic MediaSpace), and not vice versa.

Most of these cards work very well, and all come bundled with editing software. Eight of the top ten PC cards come with Adobe Premiere for Windows.

On the Macintosh, capture and compression cards have been costly until now. See the Screen Tests column for the first Mac capture and compression card under $1000, Supermac's SpigotPower AV.

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