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Desktop Video: Shooting Video for Multimedia

Shooting Video for Multimedia

You've just been asked to produce a short video training program that will be distributed on CD-ROM. Or a multimedia publisher has hired you to shoot video footage for a new computer game. Or maybe you'd just like to digitize some of your home videos for personal use. Whatever the case, computer-based video has its own requirements and limitations from both the personal computer and the video side.

Probably the most common term used to discuss computer-based video is desktop video (DTV). But the term DTV actually refers to several different technologies.

DTV may apply to videotape edited in a computer-controlled edit system like Gold Disk's Video Director. DTV also describes digital video effects (DVE) units like NewTek's Video Toaster. Non-linear edit systems, where hard disks take the place of videotape, are also called DTV systems.

PC video is a lesser known form of DTV that incorporates digitized video footage into computer programs. CD-ROM based games, reference materials and encyclopedias that incorporate video footage are the most common example of PC video. Internet-distributed video clips, sometimes called "transpixins," are another common form of PC video; you'll find these short video clips at many sites throughout the World Wide Web.

With video capture boards dropping in price and increasing in both capabilities and quality, shooting PC video can become a valuable source of additional income for the professional videographer. It can also provide a way for video hobbyists to reach a wider audience over the Internet. Whatever the medium of distribution, one thing is clear: PC video offers videomakers yet another way to present their wares.

But before you rush out and shoot some footage, there are a few things you'll need to keep in mind.

Recording Video for PC Use
The first thing to establish is how the end user will view the footage. Will it be full screen or in a window? On an 256-color computer, or on a full-color, 24-bit system? Will distribution be to the mass market via CD-ROM, or will the footage be used on a single workstation where users can tweak playback for optimum performance?

If your video is going to be part of a mass marketed CD-ROM, you're going to have to work towards a very low common denominator.

The major variables the videographer must deal with when shooting PC video are image size, image movement and image color.

Image size affects both the clarity and color of the subject you're videotaping. In this respect, we mean the image size relative to the video frame. PC video looks best when you're looking at close-up images; long shots don't come out very well on a 2 1/2-inch screen.

Image movement refers to changes in the on-screen position of the subject you're videotaping. Image movement includes moving the subject, the camera or a combination of the two.

Image color is the most frustrating variable to deal with in PC video. Many images displayed on a PC at 256 colors will have a mottled, unrealistic look. It's the videomaker's task to provide images that will digitize as realistically as possible.

Image Size
Most PC video clips being mass distributed today are 160x120 pixels in size. End users can play these clips on 386 and 486 computers or moderately fast Macs with good results. On a standard 14-inch computer monitor, a 160x120 window is 2 inches by 2 1/2 inches in size.

This small size places the first major restriction on the videographer. The tiny window limits your choice of video shots. Beautiful, majestic panoramas of mountain ranges and forests lose their visual impact when reduced to business-card-sized images on a computer screen.

Stunning visual impact may not be the major goal of your PC video clip. Enhanced communication is often the reason for including video in computer-based presentations.

One of the more popular uses of PC video is including advisors as part of an on-line help system. Many tax preparation computer programs contain help functions that initiate a video clip. These clips consist of a talking head explaining a feature of the program or areas of the tax code. From a purely technical standpoint, the talking head is easy to do with PC video and good results are obtainable even for beginners.

A good rule is to limit use of PC video to footage where the major element in the scene takes up a minimum of 70 percent of the video window size.

For example, a long shot of a taxiing jet would be useable if the plane filled up the entire video image area. If the plane were 2 miles away getting ready to touch down on a distant runway, it would be too small to be recognizable once you digitized it and played it back in a small window.

Image Movement
Motion brings video pictures to life. PC video works well with moving footage, but beware: the motion must be smooth. PC video has little tolerance for shaky movement.

PC video typically plays back from CD-ROM at 15 frames per second. PC video will skip frames to try to maintain proper timing during playback. It's not unusual for actual playback rates to be as low as eight or nine FPS.

If your footage contains unsteady camera work and is then reduced to a low playback rate on an older PC, it will look shaky and jerky. If you were trying to achieve an MTV shaky-cam look for your program, you might get away with it. But for the most part, your video will look amateurish.

If you're using a hand-held camera to shoot your PC video footage, avoid using the telephoto setting of your lens. Get physically close to your subject. Use the wide-angle position to minimize unwanted jitters or camera movement.

Zooming can be an excellent way to take your viewer from the big picture to the individual elements you want to emphasize. Remember the limitations we spoke of earlier in using wide-angle shots. Panoramas don't usually work well.

When using a zoom shot in footage destined for PC video, always think of this as two separate shots: a wide-angle shot and a close-up shot. Because of the computer screen's size limitations, make sure your viewer will be able to understand both views.

Image Color
Looking at digitized video footage can make even the most experienced videographer cringe. Once translated to that least common denominator, the most beautiful photography in the world can turn into murky splotches.

If all images consist of three primary colors, why does 256 colors look unrealistic? Because the computer processes every single shade of a color as a new color.

Imagine a basketball sitting on top of a table. The typical person would probably see it as an orange sphere. The computer would see hundreds of shades of orange. The ball would be bright orange where the light was falling on it. It would be dark orange on the side opposite the light source. The transition area on the ball between the bright spot and shaded spot could contain hundreds of shades of orange.

At 256 colors, the basketball in front of a neutral background could look pretty realistic. Put that basketball in the hands of an athlete in front of a thousand spectators, and the computer has some difficult choices to make. Remember, we can only show 256 colors at a time.

During the digitizing process, the computer creates a palette. A palette is an electronic color table. It's a list of the 256 colors that the computer has decided would best display the image. If your video is predominately one color, such as the basketball close-up example, the PC can usually render a good image by allocating about two hundred shades to that object.

In the wide shot of the basketball player, your computer will try to pack millions of colors into just 256 shades, which will reduce your picture to a blocky, unrealistic video image. If you're working with software-assisted PC video destined for playback on a 256 color system, your best choice is to avoid this type of shot.

In some instances, it's easy to control color and lighting. When videotaping talking heads, use a gray, seamless background paper and light it evenly. The trick is to allow the PC to use its resources for useful color information, and not waste a lot of those precious 256 available colors on something unimportant like a background.

Gray seamless is best because it's neutral. If gray is not available, a plain background will always give better results than a busy background.

A common multimedia production technique is to superimpose live action video footage over digitally rendered backgrounds. Some of the more expensive PC video programs may have chromakey features that allow you to shoot against a solid-colored backdrop and remove the background electronically. Then a computer-generated background can be added to your footage easily.

If your project requires this type of process, pay close attention to your lighting. Lighting is very critical in chromakey work. Bad lighting can reflect off the chromakey background onto your subject, creating halos and rough edges.

Many professionally produced CD-ROMs don't use chromakey. A more advanced (and considerably more expensive) process called "Ultimatte" gives better results.

If you need to videotape in an area where you can't control the background, try to think up ways to control the lighting. For example, if you need to videotape nature footage, try doing it around sunset. Late in the day, natural light takes on a reddish tint, which reduces the number of colors needed during digitizing. Don't be afraid to use your ingenuity to find other ways to reduce the number of colors in your scenes.

Lighting is an extremely important aspect of your videomaking. Because of the 256 color restriction, PC video can play havoc with your contrast. Digitizing may make a sharp shadow falling across a person's face more extreme; it may even change it to black and white. Elements that are hiding in shadows in your original video footage can disappear completely if the computer decides to make all shadows the same shade of gray.

The best rule to follow for lighting a shot destined for the PC is to use even lighting. Avoid hard shadows that you would normally use for dramatic effect if you were taping conventional video for VCR playback.

When shooting in natural lighting, be sure to bring reflectors and fill lights to control shadows. As with any shoot, when mixing artificial light with sunlight, make sure you properly white balance your camera.

PC Video Standards
In the video world, picture technology is fairly standard. A producer who decides to distribute a VHS videotape to the mass market can be confident that the tape will play in any VHS VCR.

PCs, however, come in such a wide variety of hardware and software configurations that it's impossible to create the perfect PC video solution to satisfy every possible computer system.

In an effort to standardize PC video so it will work on the greatest number of computers, industry leaders devised the Multimedia Personal Computer (MPC) standard. Any computer meeting that standard should be able to run Multimedia software, including PC video.

MPC Standards and PC Video
Newcomers to the PC world often assume that having the best monitor will guarantee them the best image. However, the true quality of the image you get from a Multimedia PC comes from its graphics subsystem. That subsystem consists of the monitor and a video graphics display board.

The two main measures of PC video quality are resolution and color depth.

The number of horizontal and vertical dots on the screen make up its resolution. The standard resolution for an MPC-compliant PC monitor is 640x480.

The color depth refers to the number of colors the graphics board displays simultaneously. A standard VGA board can display 16 colors at a time. VGA is called 4-bit color because the system uses four bits of memory to store each dot of the picture.

The next level in image quality is the XVGA board, which can display 256 colors. This is called 8-bit color.

The most common graphics display board sold today is the SVGA board. At its highest resolution of 16.7 million colors, SVGA is a 24-bit color system. 24-bit images are photorealistic, meaning they have as many colors as a film image. SVGA also supports 256 colors, as well as several other levels of color depth.

The current MPC standard calls for PC video to display 256 colors. That saves PCs purchased several years ago from being obsolete. While most new computers sell with 24-bit graphics subsystems, there are still millions of PCs in the marketplace that only display 256 colors.

Software-Only PC Video
Computers store PC video as digital files on a variety of magnetic or optical media. These media include, but are not limited to, hard disks, CD-ROMs, DAT tapes and data cartridges.

There are two major PC video technologies commercially available: software only and hardware assisted.

Software-only PC video includes two major formats: Microsoft's Video for Windows (VFW) and Apple's Quicktime (QT). Quicktime is available for both Macintosh computers and IBM Compatibles.

These formats will run on any MPC-standard computer without special hardware. Another feature these formats have in common is that they play in small windows on the computer instead of using the full screen. Standard window sizes are 160x120, which is 1/8 of a PC screen; and 320x240, which is 1/4 of the screen.

Software-only video uses special compression/decompression programs called codecs to reduce the size of video files to something a PC can run without specialized hardware.

Software-only video is scaled video. The codec manipulates the video to have the best possible playback regardless of the type of computer system used. For example, a typical PC video clip plays off a CD-ROM at 15 frames per second (FPS). This should run smoothly on a 486 PC. However, a 386 PC lacks the computing power necessary to play the clip at 15 FPS. The codec is constantly measuring the playback performance of the video clip and will tell the computer to skip frames if it can't play the video in real time. For a given video clip, a 386 computer may only play every other frame, where the 486 plays every frame.

Another feature of scaled video is the ability to enlarge the video picture. Remember that PC video plays in a window. A single click of the mouse can scale the 160x120 clip to 320x240 in size. Unfortunately, enlarging the picture reduces resolution, and the image becomes blocky and pixelated.

Hardware-assisted PC Video
The second major type of PC video, hardware assisted, requires a circuit board for playback. There are several types of these, usually named for the codec that they use.

The most popular type, MPEG, is a standard created by the Motion Pictures Experts Group. MPEG boards have special chips on them that allow full-screen, full-motion playback of PC video. There are no restrictions for the videomaker when shooting for MPEG playback. Because of its hardware requirements, there are very few PC video MPEG applications available. But due to recent changes in the hardware marketplace, this should change within the year.

Opportunities
According to published reports, the installed base of CD-ROM drives more than doubled from 1993 to 1994. Through the end of last year, there were over 26 million CD-ROM drives in use.

Multimedia software sales increased dramatically during 1994. While this phenomenal growth cannot continue forever, the penetration of CD-ROM (and therefore PC video)into the PC marketplace provides a new outlet for programming from both video producers and publishers.

There's also another rapidly-expanding market that uses the PC video standards discussed in this article- -the World Wide Web, where the public regularly downloads small video clips for playback on their home computers. These clips range from small corporate PR endeavors to full-length Hollywood movie previews; some Web sites have even begun to distribute weekly PC video programs.

The writing is on the wall: those producers who get into the PC video market at this early stage will certainly enjoy an advantage in years to come.

David Felder is a professional video writer and producer.


Desktop Video News &amp Reviews

Scan Lines

Write Me: Panasonic has developed a CD-ROM drive that can write and erase data thousands of times. Scheduled for release in June are several versions of the Power Drive 2, designed to help download and store the large amounts of data that make up multimedia files. The unit will hold 650 megabytes of data on disks costing under $50. Prices for all drives will be under $1000.

Super Connector: A video-to-computer interface proposed by the Institute of Electrical and Electronic Engineers (IEEE, standard P-1394) has become recognized throughout the industry. It's capable of moving over 100 megabytes of data per second, which developers say will quadruple in the next year. Developed by Texas Instruments and Apple Computers, the standard gets the name Firewire #153 in the Apple product line. Sony and Panasonic are considering product development using this standard.


Product Menu

Perception Video Recorder ($1995)
Digital Processing Systems
Florence, KY 41042
(606) 371-5533

The Perception Video Recorder is a high-quality PCI-based digital video disk recorder system that includes 10-bit video encoding, CCIR 601 4:2:2 processing and SCSI disk control. Other card features include multi-platform support (through Windows NT based software) for Intel, DEC Alpha and MIPS processors. Only the number of drives limits the record time. $999 gets a daughterboard for capturing real-time videos.

Fastedit A/B-roll Editing Studio($9995)
Selectra Corporation
Walnut Creek, California
(510) 284-3320

Here's a full-blown turnkey A/B-roll editing system put together by Selectra Corporation that's affordable yet means business. The system includes three Panasonic AG-1970 S-VHS editing VCRs, three Panasonic CT-1384Y 13-inch monitors, one Panasonic C-1491 computer monitor, a 66MHz 486 computer and Fast's Video Machine Lite. Together, this offers you a graphical timeline interface, a six-input video mixer, eight audio channels, titles, vertical interval time code (VITC) support, a DVE editor and 200+ effects.

StoryBoard Artist ($499)
Power Production Software
Hermosa Beach, California
(310) 937-4411

This professional storyboarding software for use on Macintosh computers will allow anyone using video to make simple sketches or full-color graphics. The software uses pre-drawn characters that you can rotate and place in various locations. StoryBoard Artist offers six frame ratios. Each has caption, dialog and video description windows. A slideshow feature (with dissolves) and music makes showing of demos easy. Requires system 7 or better and 4MB of RAM.

MVP (MPEG Video Producer) ($695)
Visual Circuits
Minneapolis, Minnesota
(612) 781-2186

Here's an MPEG playback board for animators that offers full-screen, true color animation playback at 30 fps. Used along with the included software, you can compress animation sequences into MPEG files or synchronize CD-quality audio with video and combine it into a single file. You can use the software to compress up to 72 minutes of video and CD-quality audio on a 650MB hard disk.

Tags:  September 1995
Dave
Felder
Fri, 09/01/1995 - 12:00am