Glossary of Home Theater Terminology
Glossary of Audio, Video and Home Theater Terms
There is a very large vocabulary of technical and descriptive terms that go with home theater. We've included the terms that you are most likely to encounter. If you are very technically involved you may find some of the more technical terms omitted from our list.
Layer Change - A DVD contains up to two data layers on each side. Each data layer can hold about two hours of NTSC video. Movies longer than two hours long or encoded at a high data rate, are spread across the two layers on one side of the DVD. The laser is refocused to play the second layer and when the player changes to the second layer, the video and audio may freeze momentarily.
LCD - Liquid Crystal Display. A panel consisting of two transparent polarizing panels with a liquid crystal material sandwiched between. When voltage is applied, individual crystals turn dark. Behind the panels is a light source which flows through clear crystals and is blocked by dark crystals. The pattern of off and on crystals creates the image.
LCoS - Liquid Crystal on Silicon. While similar to LCD projection technology, instead of blocking or allowing light through (as in LCD projectors), LCoS applies liquid crystals onto a silicon chip which then either reflects or doesn't reflect the light. Three chips are used, one for each color, which in better picture quality and eliminates problems such as the"rainbow" effect.
Learning Remote - A form of universal remote that can control all the devices in a home theater from a single controller. A universal remote control can be programmed with control codes for broad range of devices. A learning remote adds to this ability by being able to "talk" with the original remote. By placing an original remote head-to-head with a learning remote, the signal from the original remote is learned and assigned to a button on the new remote.
LED - Light Emitting Diode. Used as an indicator light in many devices for many years, it is now also being employed as the light source in LCD (LED) televisions. LCD TVs have typically used fluorescent backlighting, but LED backlights have many advantages and may ultimately replace fluorescent backlights.
Letterbox - Because some images, such as wide-screen movies, do not fill a TV screen, black bars are placed above and below the image to fill the unused space. This allows to movie to be shown in its native aspect rather than being adjusted to fit the screen. When bars are placed to the left and right sides of an image it is called windowbox.
LFE - Low Frequency Effects or the bass audio signal. Generally the signal between 20-150Hz that is played through a subwoofer.
Line Doubler - A device, or circuit in a device, which converts interlaced video to progressive scan video. Interlaced pictures are painted in two passes. Every other line is painted in the first pass and the alternate lines are painted on the second pass. A line doubler, aka deinterlacer, creates a complete picture, filling in all of the lines, for each scan. More lines results in a better picture.
Lossless Compression - A compression algorithm that doesn't lose any of the original data. The original image or sound is completely preserved.
Lossy Compression- A compression algorithm that removes some data, to reduce the file size, while preserving the sound or image. Data that is removed is lost, thus altering the original image permanently.
Loudness Compensation - A feature on many receivers that attempts to compensate for the loss in low-frequency sound at lower volume levels.
Luminance - The brightness portion of a video signal, represented as "Y". The luminance signal carries the picture detail information and can produce a complete black and white image. When combined with the chrominance signal or component color signals a complete color image can be displayed.