High Tech Times- Creating a Digital Video

High-Tech Times Article 003

Creating a Digital Video

I'll bet that all of you have at one time dreamed about being a video producer and creating a TV show that lets everyone know just how talented you really are. Today, you can do just that using your desktop computer system. For many years, the television industry made us all think that it took millions of dollars of cameras, brand-name talent, and sharp-eyed directors to make a movie. Once you realize that video is just one more of the data types that we work with on our computer every day, you can start planning your video upgrade.

Although digitizing (capturing) video is not a complex task, it does create very large files, and works your computer's processor a lot. So you will want to start out with a Pentium-class machine (the more powerful the better!) with a minimum of 32 MB RAM and a very fast hard-drive. Video is one of the few areas that takes full advantage of Intel's MMX (Multimedia Extension) processors, so if you have the choice between, say, a standard Pentium 200 CPU and one with MMX, choose the MMX processor for another $25 or so.

Your computer's memory is a major decision on a digital video system. There are a number of types of available RAM, including EDO and Fast-Page, either of which will work well in this video system. The hard-drive is probably the biggest factor in a well-functioning video digitizer. The standard Integrated Drive Electronics (IDE) hard-drives cannot handle the huge volumes of data generated by the video stream.

Let me take a moment and illustrate the quantities of data we're talking about. Television-type video is created at 30 "frames" each second (30 fps), each of which consists of a screen with a resolution of 720 X 486, and 16.8 million colors (24-bit). So one single second of uncompressed digital video is 30 X 720 X 486 X 24, or 252 million bits/second (31.5 MB/sec). You can quickly calculate that one minute of this video stream would just about fill your 2 GB hard-drive! I will discuss compression schemes, but let's first get back to your hard-drive.

A standard IDE drive handles a data stream of about 3-5 MB/second, while one of the new Ultra-IDE drives raises that to around 15 MB/sec. However, I recommend that you give serious consideration to a SCSI (Small Computer Systems Interface) hard-drive rather than IDE for several reasons. First, you can chain seven SCSI devices, compared to only four on IDE. Second, even the slowest current SCSI drive (called SCSI-2) is faster than nearly all IDE drives. Third, the fastest Ultra-SCSI-3 drives support a data stream of more than 40 MB/sec. And, last, SCSI drives offer AV-rated models that are made to support the audio-video functions we're discussing.

Okay, so you have your brand new 300-MHz Pentium II computer with 64 MB of RAM and a 4.3 GB Ultra-SCSI-3 AV hard-drive running Windows 95: what do you do now? We still need two more key parts: the digitizing interface board and video authoring software.

The video digitizing board is where we separate the broadcast professionals from the "prosumers." A full-motion (30-frame/60-field per second), full-screen (720 X 486), full-color (24-bit), broadcast-quality (at least Beta SP, and preferably D-1) PCI-based video digitizer board will cost at least $7,000. A high-end prosumer board will still cost from $2,000-$5,000, while giving up broadcast-level outputs, and having VHS and SVHS connectors. There are many low-end (consumer) boards available, but if you're serious about creating high-quality video, you should plan to budget at least as much for the video digitizer board as you do for the computer itself.

The video authoring software takes the video "clips" that you capture and assembles them into a final video "movie." Those of you who have used Adobe PageMaker, for example, understand that you create graphics, business charts, and text in different applications, and then use PageMaker to create a final page-layout. Adobe also makes a software package called Premiere that does the same job for video and graphics clips.

Adobe Premiere runs on both Windows and Macintosh platforms, so you can instantly interchange video files from one to the other. I personally prefer dual-platform software, as it makes my job much easier.

In Premiere, you can operate most video digitizing boards, or you can use the software that came with the board to capture your video clips. Once you have a "library" of video clips (ideally saved in the same subdirectory), you use Premiere to open them up and arrange them in the order you prefer. I don't have sufficient time to teach Premiere in this column, but let me just say that it's really quite easy to assemble video clips, still-image graphics, and even audio clips into a high-quality video movie (my son was an expert by the time he turned 15).

Let me return to the methods used in capturing video. Both broadcast and prosumer boards offer "video compression" techniques that reduce the size of digitized files to a (relatively) manageable size. The trick to video compression is to reduce the file size (and resulting data-stream) while leaving the final product without video "artifacts." An artifact is a visible flaw in the final movie that detracts from its effectiveness.

Those of you who use graphics software are probably familiar with JPEG (Joint Photographic Experts Group) compression that is used with still images. JPEG files can be compressed into a file up to 100 times smaller than the original, but only 2-3 times without causing image artifacts. Similarly, video uses MPEG (Motion Pictures Experts Group) or MJPEG compression to reduce file sizes.

You should always try to limit the amount of compression in your video processing, but if you need to create a 10-minute video show, you may need to compress more just to fit it onto your hard-drive (I can fill my dual 9 GB AV hard-drives in less than a day's video processing!). I suggest that you run a series of tests using your specific board and software to determine the optimal compression ratios for your system.

Another way to reduce file size is to look at the TV screen that you'll be showing your movie on. Standard televisions allow you to view only 512 X 486 resolution, which is nearly 30 percent smaller than the full 720 X 486 broadcast resolution, so you may wish to digitize at, say, 640 X 480 to save space and speed things up.

Once you have created your video masterpiece, it can be distributed on standard videotape (VHS and 8mm to SVHS and Hi8), CD-ROM, or even over the Internet. I am currently working on a project for the National Kidney foundation where we are using digitized video as part of a Macromedia Director presentation that will be distributed on CD-ROM.

Remember that once you have created a full-screen movie, you can always "resample" it at a lower resolution without losing image quality. For example, if I have a 70 MB video movie that I want to run at quarter-screen, I can use Premiere to resample it at 320 X 240, and the resulting file size will be only 17.5 MB or so. Don't try to go the other way, though; the artifacts created by going from 320 X 240 to 640 X 480 will make your movie look more like a jumpy screen filled with weird-looking blocks than you would believe. Good luck!

If you would like to see a demonstration of video digitizing, or if you have topics that you would like to see discussed in High Tech Times, please feel free to call me at (808) 521-2259, or you can e-mail me at kgold@aloha.net.