dB (Decibel)

Decibels are most often used to describe sound pressure level (commonly referred to as volume). The term is also used in various other measurements such as signal-to-noise ratio, gain and dynamic headroom. In these instances, decibels refer the measurement of signal increase or signal strength instead of sound pressure level, but the scale and basic idea is the same.

Digital Surround Sound

Digital surround sound is a format in which all five audio channels (left front, front center, right front, right rear, left rear) are separate and full-range, recorded in digital audio, and compressed to fit in a smaller space. A subwoofer is an additional (optional) channel, but it is not full range.

Digital Audio

Digital audio is a method of encoding analog audio signals into digital bits of information. Digital information is easy to transmit and record, and can be modified or adjusted quickly without signal degradation. The most common form of digital audio is the compact disc (CD). Digital audio can be compressed to save space.

DAC (Digital to Analog Converter)

When an analog signal is recorded onto a digital medium, it is split up into thousands of very thin slices. Each of these slices is given a height and an order, and then the information is digitally stored. When digital signals are played back, the thousands of slices are lined up in the proper order. The digital to analog converter forms a solid, flowing line from the tops of the slices to create a continuous, analog waveform.

Most digital components include a digital-to-analog converter.

Digital

Digital refers to a type of signal, which is composed of individual bits, or chunks, of information. An analog signal is a continuous waveform signal. Digital signals are easier to manipulate and store, and have much less distortion than analog signals.

Digital Television

Digital television refers to video displays that can display digital video signals. ATSC, digital video broadcast standards, were adopted by the FCC to replace the analog NTSC format. This standard includes 18 formats; 6 high definition (HDTV) formats and 12 standard definition (SDTV) formats.

Direct View Video Display

Direct view is a video display in which the light produced by a cathode ray tube is viewed directly without being bounced off a screen (as in a projection TV). Direct view is similar to looking directly at the light coming from a flashlight instead of looking at the light as it bounces off the wall. Direct view displays have better light output than projection displays. Most televisions and computer monitors are direct view displays.

DLP (Digital Light Processing)

DLP is a digital video display technology. DLP rear projection video displays weigh much less than traditional displays e.g., a CRT or PTV) and are much thinner. Because of this, and because of DLP’s excellent image quality, DLP displays can be quite large.

DLP uses thousands (approximately 500,000) of tiny square mirrors. Each mirror represents one pixel, or picture element. Each mirror pivots on or off to reflect or not reflect red, green and blue light to create an image on the screen.

The mirrors are contained on a small microchip called a DMD (Digital Micromirror Device). Digital light processing systems are capable of displaying 16.7 million colors or true color.

DLP projectors may use one, two or three DMD chips. Three-chip designs split the three additive primary colors so that each chip reflects only one color of light. Three chip designs are the most costly but also output the most light with the highest quality.

One-chip designs use a single mirror for all three colors of light. The picture from a one-chip design is not as bright or detailed as the picture from a three-chip design.

Two chip designs have a higher light output than a single chip design, but are not as costly as a three-chip design.

The DLP system was developed and is licensed by Texas Instruments. DLP video displays are the highest quality currently available.

Dot

    A dot is single spot or dot of phosphor found in a cathode ray tube (see CRT).

Dot Crawl

    Dot crawl is picture distortion caused by poor filtering; a line of dots (single spots of phosphor on a cathode ray tube) shifts continuously where there is a sharp color separation in a vertical line. Most often, this occurs with composite video.