Home Theater Video
In this section we describe the video components of our Home Theater system.
Screen A front projection
screen can be motorized to roll down from its housing right before showtime, or fixed
permanently to the wall with aluminum frames. Screen sizes range from 5-foot to 15-foot
when measured diagonally.
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The reflective characteristics of a screen, called the gain, determine how far
off center people can sit from the screen and still enjoy a crisp, bright picture.
Generally, the lower the gain, the better the picture quality at all viewing angles. A screen with a gain of 1.0 for example, imparts a bright image so that people sitting at the edges of the screen can see the picture almost as well as people sitting in front of it. A screen with a gain of 2.0 on the other hand, may require that everyone crowd near the center of the screen for a good seat. |
DVD was designed to be a
replacement to VHS and CD's. This 4.72-inch (the same size as a standard CD) marvel of
modern technology was first conceived in 1994 by an alliance of companies comprising of
Sony, Philips, Toshiba, and Time-Warner. Surrounded in the controversy that most new
standards evolve in, it took three years to bring this ultra-complex digital-video wonder
to market.
A single DVD by using smaller data-storage pits than a CD, and placing them closer together, is able to hold 4.7 gigabytes of data ( a term meaning approximately 1 billion bytes), nearly eight times the capacity of a standard CD, on a single layer of a single side (more on the layers in a minute). However, even this huge increase in storage capacity would not be enough to hold a two-hour movie, so the Motion Picture Experts Group (MPEG) digital compression ( sometimes called bit-rate reduction) is employed to shrink the video data into an even smaller package.
Digital compression takes advantage of digital manipulation techniques to reduce the size of the data package. Rather than reproduce every frame of every movie, each additional piece of data includes only the changes from the previous frame. For example, if the scene is of a star field in space, and all that happens for one minute (1440 frames) is that a space ship flies past one part of the screen, just one copy of the full frame scene is stored. The other subsequent data is only made up of the ships movement. (This is actually a very basic description of how this works, but should give the general concept.) Using this technique means that action sequences take up a lot of data space, while those made up of talking heads occupy very little data space. (The compression of video has already started some discussions on the web regarding the quality of DVD as compared to Laserdiscs. It seems that in some lower quality software "video dropouts" and blurring can occur. See pictures below)
The results space for 133-minute-long video presentation -- that's nearly 92% of all Hollywood movies ever made --and from just one side. This also may include a Dolby Digital audio soundtrack, three different language selections and four subtitled languages. If fewer languages or subtitles are included, even longer running times are possible. The format allows for up to eight soundtracks and 32 sets of subtitles, but if all of these are implemented, the space available for video is reduced to less than 133 minutes.
Unlike the satellite dish of the past Digital
Satellite Systems (DSS) are a lot smaller (18") and are more technically advanced.
They receive a digital signal that carries a superior image similar to a laserdisc. The
sound quality is also comparable to CD.
DSS are easy to setup and tune and, they will be able to receive future television standards, such as HDTV and six-channel sound.
Monthly service plans are usually cheaper (on a per-channel basis) than cable TV service.