Using Media Equipment for Presentations

Once your multimedia projector and screen are installed in your worship facility, you will want to consider the media content and format that will be supplied to the projector. To get the most out of your presentation, it is essential to consider the media equipment and the format that equipment will present.

VHS/DVD
Probably the oldest source for a multimedia projector is the Video Cassette Recorder. Many people still have in-house educational or entertainment media in the VHS format. The VHS media signal is normally sent to the projector by means of a composite video cable with RCA type connectors at each end. Longer runs of composite cable (over 50 feet) may require signal boosting, as the signal can become noisy or "snowy" as distance increases down the line. Composite video is called such because the one signal on the cable is "composed" of the black and white video signal (luminance), the color signal information (chrominance), and the timing or synchronization (sync) signals. Also, unless the projector is being used in a very small room, the audio signals are interfaced with a sound system, and no audio cables are run to the projector. Still, most projectors do have a very small wattage audio amplifier, so it can be used in small, localized room or area. Some higher-end VCRs have the option of what is called S-Video, discussed with DVDs.

The DVD (Digital Versatile Disk) player usually has at least three outputs for the video signal:

1. Composite Video
2. S-Video (Super Video)
3. Component Video

Composite video has been covered above. Of the remaining video formats, S-Video is the older and most popular of the two, being on every DVD player and most televisions with screens of 25 inches and larger. S-Video is capable of carrying the video signal further with less cable loss. This is because, in S-Video, the luminance and the chrominance are sent as separate signals, which can eliminate some of the noise or "artifacts" in the imaging.

Component Video is the highest form of analog video the DVD player will provide. Most new DVD players have component video outputs. The signal is routed via three RCA connectors, which are marked red, green, and blue. The video is sent as a luminance signal, and two chrominance signals. Component Video provides an even higher quality picture than S-Video. Distance runs may be as long as an S-Video, on the order of about 100 feet. The only drawback is that three separate cables must be run for the signal, but for those who have a projector capable of component video, the quality of the signal can outweigh cost concerns. Component video can also be sent in a progressive scan mode, which shows each line of video sequentially rather than interlaced odd/even like analog television. Progressive scan gives a more detailed image.

Video Graphics Array (VGA)
The use of computers as sources for multimedia projectors has made a large impact on presentations today, allowing virtually unlimited content either by Internet or by the use of presentation software. Computers output a different form of analog signal format, called video graphics array, or just VGA. The signal has separate red, green, blue, and both horizontal and vertical sync signals. This is actually the highest form of analog video. VGA can be sent in several different quality levels. Each VGA image is composed of dots, or pixels on horizontal lines, and vertical columns of lines. A resolution of 800 x 600 would be 800 pixels per line, and 600 vertical lines, or "columns." Resolutions can be made higher by increasing the pixel/line count, such as 1024 x 768. Some common resolutions:

* VGA 640 x 480
* SuperVGA (SVGA) 800 x 600
* Extended VGA (XGA) 1024 x 768
* Super Extended VGA (SXGA) 1280 x 1024
* Ultra Extended VGA (UXGA) 1600 x 1200

It is important to remember that the higher resolutions will lose quality quicker than the lower resolutions for a given distance cable run. The cables used have 15 pin male connectors and are available in lengths up to 100 feet. VGA line amplifiers or "boosters" are available to increase signal strength for long cable runs.

DVI
Some multimedia projectors are provided with a connection to receive a digital video signal. The Digital Visual Interface (DVI) can provide outstanding graphics arrays from a computer. Both computer and projector must have the interface to operate. The connection is a 24 pin connector and may have an additional 5 pins to also carry an analog signal in the absence of digital data. This would actually be called DVI-I for both digital and analog. Many multimedia projectors that support high-definition signals used in digital television use the DVI as the interface. DVI signals degrade quicker over distance runs, as compared to VGA, so this interface is usually limited to short-run applications.

Camcorders as Media Equipment
A camcorder can supply a video output to a multimedia projector by means of a composite or S-Video signal. Multiple camcorders can be run through a video mixer switcher, and the appropriate source video chosen.

Visual Presenters as Media Equipment
A visual presenter is a video camera like a camcorder, but it has been optimized to provide a close-up view over a small area. This makes it ideal as a presentation tool for viewing small objects or printed material. Unlike a presentation where only pictures of an item are seen, the actual item itself is present, allowing for more in-depth detail study. Visual presenters are very popular in school use, such as science departments or shop classes. Visual presenters interface with the multimedia projector by means of composite or S-Video, and some are capable of also supplying VGA signals.

Audio from Media Equipment
Many media sources supply audio signals for the presentation. The VCR and DVD player usually have a pair of RCA connectors to output left and right stereo audio. The computer has a sound card to output its audio from a 3.5 millimeter stereo jack. The audio signals from media equipment are output as line level (1 volt). As stated before, the multimedia projector has a small one-watt or two-watt sound system that can be used in a small room. For larger venues, it is best to route the audio to the input of a more powerful sound system or powered speaker.

Proper use of media equipment makes the presentation more dynamic and interesting and assures the successful delivery of information to your viewing audience.

This article is courtesy of Long's Electronics, Inc., www.longsav.com.