Classic Computer Magazine Archive COMPUTE! ISSUE 164 / MAY 1994 / PAGE 66

How to use desktop video. (includes glossary) (Multimedia PC)
by David English


Some predictions of the future just won't go away--flying cars, wristwatch telephones, and desktop video. Flying cars will probably never appear in our lifetime, and wristwatch telephones are still about five or ten years away. But desktop video is here now--and about to become a much larger part of everyday computing.

So what is desktop video, how does it work, and how can you use it? Just as a sound card converts analog sound into digital sound that can be manipulated and stored by your PC, a video capture card converts analog video--from a VCR, camcorder, or television-- into digital video that your PC can manipulate and store.

There's only one catch. Video contains too much information for a personal computer to deal with. In its raw form, 320- x 240-pixel video at 30 fps (frames per second) with 24-bit color would take up about 6.6 megabytes per second, 395 megabytes per minute, or 2.37 gigabytes per hour. PCs simply can't process that much information at a time. The solution for this problem is compression, without which there would be no desktop video.

The Big Squeeze

As it is, even with compression, we're pushing the limits of our processors, so some compromises have to be made. Three main factors determine the quality of the video: the speed of the processor, the video's frame rate, and the size of the video window. Increase the processor speed, and you can increase the frame rate (for less jerkiness) or the size of the video window (for a larger image). Increase the size of the video window without increasing the speed of the processor, and you'll have to drop the frame rate (if you don't, the software will randomly drop frames, making the video even jerkier). See "Video Playback Performance with the Indeo 3.0 Codec" for more details.

Add three other factors--the number of video colors (8-bit, 16-bit, or 24-bit color), the quality of the video sound (8-bit or 16-bit), and the type of compression (even within a compression scheme, there are trade-offs between the amount of compression and the quality of the images)-- and you have a complicated balance of component parts.

Fortunately for Windows users, this is all taken care of by Video for Windows. If you have a CD-ROM drive and regularly try out CD-ROM titles, you should already have the player portion of Video for Windows. This includes the playback engine and a variety of codecs (compression/decompression drivers). Video for Windows 1.1, the most recent version, includes the following codecs: Cinepak from SuperMac, Indeo from Intel, RLE from Microsoft, and Video 1 from Media Vision and Microsoft.

All, with the exception of RLE, are lossy, which means they sacrifice picture quality to achieve higher orders of compression. This quality is permanently lost--when you decompress the file, it doesn't go back to its former quality. RLE, on the other hand, is lossless, which means there's no loss in image quality. As you might guess, the lossy methods achieve much higher compression ratios and allow you to play back your video at higher frame rates or in a larger window.

Because Video for Windows takes care of loading up the correct codec when you run an AVI file, it essentially guarantees that all Video for Windows video input boards will be compatible with all Video for Windows codecs. Quick Time for Windows works pretty much the same way. Its codecs, many of which are identical to ones included with Video for Windows, are also interchangeable and work with any Windows application that supports its MOV files.

Video for the Masses

At this point, you may be wondering what all this has to do with you--after all, you don't plan to develop multimedia applications. Think of it as using text and graphics files with your computer, even if you're not a professional writer or graphic artist.

Many of the new CD-ROM programs use Video for Windows or QuickTime for Windows video files. Popular titles include the major encyclopedias (Microsoft Encarta, Compton's Interactive Encyclopedia, and Grolier's Multimedia Encyclopedia), reference works (Microsoft Cinemania, Movie Madness, 20th Century Video Almanac, and World View), and even complete movies (It's a Wonderful Life and A Hard Day's Night). The video files usually have either AVI extensions (for Video for Windows) or MOV extensions (for QuickTime for Windows). A monthly magazine on CD-ROM, called Nautilus CD (Metatec, 800-637-3472, $137.40 a year in the U.S. and $222.00 a year outside the U.S.), regularly includes 100 megabytes or more of AVI files, such as music videos from popular groups, multimedia tutorials, and promos for computer products.

To view these files outside your CD-ROM application, you'll need to associate the file's extension with a program that can play the file. For example, if you want to associate AVI files with Windows' Media Player, you would run File Manager, select an AVI file, choose File from File Manager's menu, choose Associate, type c:~windows~mplayer.exe under Associate With:, and press the OK button. You should then be able to double-click on any AVI filename from within File Manager to automatically play the file. (Assuming Windows is set up to handle them, you can associate Media Player with other multimedia files, such as QuickTime for Windows video files and MIDI music sequences.)

Media Player includes a set of VCR-like controls that let you play, stop, fast-forward, and rewind your video sequence. Under the Device menu selection, you can choose Configure and experiment with different settings, including doubling the size of the video window and skipping frames when the video falls behind.

If you find a video sequence you like, you can copy it over to your hard drive--assuming you have the space for it. You'll soon notice that even a 30-second compressed video file can take up from three to five megabytes on your hard drive. If you're running Stacker or DoubleSpace, video files can take even more space (because video files are already highly compressed, they lower your compression ratio and so appear to take up more room than they really do).

Roll Your Own

Like to create your own video files? No problem. All you need is a video capture card, such as the VideoSpigot (Creative Labs, 800-998-5227, $399.95), Pro MovieStudio (Media Vision, 800-845-5870, $449.00), Smart Video Recorder (Intel, 800-538-3373, $699.00), Vidiola (Orchid, 510-683-0300, $399.00), or Video Blaster (Creative Labs, $499.95). All ship with Video for Windows, so you'll be able to try out the different codecs and select the compression scheme that fits your needs. Most of these cards will let you capture video at 320 x 240 at 15 fps and 160 x 120 at 30 fps, compress the video either in realtime or after capture, and store the compressed video to your hard drive as an AVI file. If you don't have a fast 486 and local-bus video, you may have to drop down to 240 x 180 at 15 fps, or even 160 x 120 at 15 fps--otherwise, you'll drop a lot of frames as you capture the video.

The standard video frame rate for television is 30 fps in the U.S. and 28 fps in Europe. Films are shown in movie theaters at 24 fps, though silent films varied from 16 fps to 24 fps. For most uses of desktop video, 15 fps is considered acceptable. With 10 fps, there's a slight jerkiness that--depending on the material--may not be too bad. Any rate under 10 fps causes the video to look like a fast-moving filmstrip.

Almost all video capture cards include the playback and basic editing programs from Video for Windows. Because these cards now ship with the Video for Windows utility programs, Video for Windows 1.1 is sold only to developers.

For anything more than basic cut and paste, you'll need a full-fledged videoediting program, such as Adobe Premiere (Adobe, 415-961-4400, $295) or MediaMerge (ATI Technologies, 416-882-2600, $295). Both let you combine video clips with a variety of special effects and save the results as a new video file. Both can read Video for Windows and QuickTime for Windows files, but only Adobe Premiere can save in both formats.

Adobe Premiere comes with over 35 image-processing filters, including antialias, brightness/contrast, emboss, radical blur, and sharpen edges, as well as 35 effects and transitions, including cross-dissolve, zoom, band wipe, venetian blinds, and cross-stretch. MediaMerge includes fewer features--it has only 9 transitions, for example--but it comes with a separate WAV file audio editor, an integrated text animator, and a CD-ROM full of useful videos, animations, sounds, photos, and backgrounds you can use in your video productions.

Even though it doesn't have all the features of its $795 Macintosh cousin, the Windows version of Adobe Premiere is still a powerful program. You can insert one video image into another (for a picture within a picture), create split-screen videos (using mattes of various shapes), customize transitions (using a transition twice to simulate a new transition), intensify the effect of a filter over time (by splitting the clip into several pieces, applying the filter to each individual piece, and rejoining the pieces), superimpose a person against a background (similar to the Chroma key technique used to place a weather-person in front of a weather map), produce a rotoscoping filmstrip (using Adobe PhotoShop to mark up individual video frames and send the video back to Adobe Premiere), and even create a 360-degree video presentation (simulating a three-dimensional space with a movie playing on each of five walls).

Other programs you might find useful for manipulating your desktop videos include Matinee (Access Softek, 510-848-0606, $49.95 for disk version and $59.95 for CD-ROM version), which lets you use your AVI files as a screen saver; SoundTrack (Access Softek, $79.95), which lets you record and overdub sound onto AVI files; 3D-IT (Electronic Imagery, 305-968-7100, $99.95), which lets you take ordinary AVI files and convert them to 3-D movies (the kind that need the funny red- and blue-lens glasses); and MCS Stereo (Animotion Development, 205-591-5715, $79.95), which lets you add QSound to WAV-format sound files for a true 3-D sound.

Calling Captain Video

Now that you've created a stunning video sequence, what do you do with it? Can you really create the kind of videos that you see on MTV? Currently, you're pretty much restricted to 320 x 240, which is one-fourth of a standard 640 x 480 screen. AuraVision has developed a special chip that can intelligently blow up 320 x 240 videos to fullscreen, without the usual big-pixel effect. Orchid's Vidiola line of video capture boards uses this new chip. Hardware-assisted fullscreen video is available now, but only in expensive video boards. Look for their prices to fall, providing less expensive boards this year or next.

In the meantime, you can take your video files and embed them into Windows documents with OLE, as well as combine them with other multimedia elements using one of the many new multimedia presentation programs, such as Compel, Action!, Harvard Graphics for Windows, and Astound.

Using OLE, you could write a letter to your sister in Alaska and embed a video clip of your two kids saying, "Wish you were here." Any Windows program that supports OLE can accept an embedded AVI file. Using a presentation program, you could create an interactive training program, a tour of your new business, or a family album including interviews with the eldest members. Table: Video Playback Performance with the Indeo 3.0 Codec Processor 640 x 480 320 x 240 160 x 120 486SX/25 1 fps 15 fps 30 fps 486DX/66 10 fps 30 fps 30 fps Pentium 20 fps 30 fps 30 fps

One problem: Even with compression, video files can be many megabytes in size, so how do you get that five-megabyte letter to your sister in Alaska? One solution is to use one of the video codecs that let you trade off the degree of compression with the level of quality. Most codecs offer a compressor setting for quality that goes from 0 to 100 percent. It's typically set somewhere between 65 and 85 percent, but you could set it lower and further compress your file. The other solution would be to optimize the way you send your document. Many backup programs will let you split a large file onto many floppies, or you could send a backup tape to someone who's using the same kind of tape backup system.

At this point, desktop video is still in its infancy. With the initial release of Video for Windows, all you could practically do was 160 x 120 videos. Now, with the improved Video for Windows and QuickTime for Windows codecs, most new PCs can handle 320 x 240 videos, with 640 x 480 videos just around the corner. And with powerful programs such as Adobe Premiere and the soon-tobe-shipping Passport Producer for Windows, the world of PC-based digital video editing is finally opening up to the casual user.


AVI. Short for Audio/Video Interleaved. The video file format used by Video for Windows.

codec. Short for compression/decompression. A driver used by Video for Windows or QuickTime for Windows that compresses and decompresses video files.

compression. The process of reducing the size of a video file either with no loss of quality (lossless) or with some limited loss of quality (lossy). See also lossy and lossless.

desktop video. Computer-based digital video usually associated with high-end full-screen video production. Much as the term desktop publishing is used to describe the ability to create, edit, and store textbased documents with a personal computer, desktop video is used to describe the ability to record, manipulate, and store video with a personal computer.

fps. Short for frames per second. The speed at which a sequence of pictures is played back. Frame rates higher than about 15 fps give the illusion that a series of still pictures is actually a continuously moving image. Standard frame rates include U.S. video at 30 fps, European video at 28 fps, sound film at 24 fps, and silent film at 16 fps to 24 fps.

lossless. A compression method that allows compressed files to be decompressed to their original form with no loss of quality. Because it doesn't sacrifice quality, a lossless method of compression will generally result in a much larger file than a lossy method of compression. See also lossy and compression.

lossy. A compression method that compresses files with some limited loss of quality. Because it sacrifices quality, a lossy method of compression will generally result in a much smaller file than a lossless method of compression. See also lossless and compression.

MOV. Short for movie. The video file format used by QuickTime for Windows.

QuickTime for Windows. A set of software programs from Apple that allows Windows to play motion video sequences on a personal computer without specialized hardware. QuickTime for Windows has its own set of compression/decompression drivers (called codecs), similar to those found in Video for Windows, and plays video files with the MOV extension. See also codec, Video for Windows, and MOV.

Video for Windows. A set of software programs from Microsoft that allows Windows to play motion video sequences on a personal computer without specialized hardware. Video for Windows has its own set of compression/ decompression drivers (called codecs), similar to those found in QuickTime for Windows, and plays video files with the AVI extension. See also codec, QuickTime for Windows, and AVI.