Technical Glossary
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Displaying 81 glossary terms found.


The second of two essential parts of a theatre’s sound playback system, starting from the A-chain and consisting of channel equalization, amplification, and transmission of the audio signals to the theatre speakers. See A-Chain.

Broadband Integrated Services Digital Network. A special version of ISDN that uses fiber optics and can transfer at 1.5 megabits per second. See ISDN.

B-Y Signal
A color mixture close to blue with 180° phase opposite to color sync burst. Bandwidth is 0 to 0.5 MHz.

Back Porch
The time in a composite video signal that is between the trailing edge of the sync pulse and the trailing edge of the

Background Noise
Extraneous sound which is noticeable or detectable during sound recording or playback. For example, in a theatre there can be noise from air-handlers, projectors, or sound spilling over from an adjacent auditorium.

1) A device used to inhibit the propagation of sound waves. Baffles are usually vertical hanging panels used to reduce reverberation time. 2) An acoustical seal which prevents the air from the front of loudspeaker from mixing with the air from the back of the loudspeaker to prevent a loss of bass response.

Baffle Wall
A design specification of the THX Sound System consisting of a floor-to-ceiling structure between the screen and rear wall. The baffle is constructed of a thick drywall material plus an acoustic panel braced to the wall structure. The purpose of the baffle is to ensure that low frequency sound propagates directly into the theatre while serving to absorb high frequencies that are reflected behind the screen to prevent echoes that can interfere with dialogue intelligibility.

1) The uniformity of frequencies or relative loudness between the left- and right-channel or front- and back-channel audio signals. 2) The control that changes balance.

Balanced Audio
A method that uses three conductors for one audio signal. They are plus (+), minus (-) and ground. The ground conductor is strictly for shielding, and does not carry any signal. Also called “differential audio” and “balanced line.”

A range of frequencies between two definite limits. Bands are assigned by the Federal Communications Commission (FCC) for a specific use.

Band Pass Filter
BPF. A circuit, commonly having inductance and capacitance, that effectively passes a given range of frequencies. Frequencies above and below this range are attenuated.

Radio, TV, audio and video all use different frequencies in which they operate. When such equipment is designed, it is intended to work with a certain range of frequencies. This range, or “band” of frequencies, is called a bandwidth. The bandwidth is the range of frequencies that is allowed to pass through the device, while frequencies above and below the bandwidth are rejected. The frequency range, or “band” of frequencies between the limits are defined by the “half power points,” where the signal loss is -3dB. In audio and video, it is this band of frequencies that can pass through or be reproduced by a device without significant loss or distortion. The wider the bandwidth, the better the quality that results, such as a sharper picture, better sound, etc. The higher the bandwidth number, the better the performance. (300 MHz is better than 250 MHz.) When a signal passes through a path with more than one device (including cables) the limiting factor (bottleneck) in that path is the device with the narrowest bandwidth. In a digital circuit, bandwidth capacity is usually measured in bits per second (bps). In a display device bandwidth is an index of how many bits of information a display device can process every second. The units for bandwidth are expressed in kilo Hertz (kHz).

The outward curved edges on a display image. See Pin Cushion.

Barrel Connector
An adapter used to connect two coax-type connectors of the same gender.

Barrel Distortion
A geometric distortion in which the middle of lines near the borders of the screen bend outward.

Something that separates, demarcates, or serves as a barricade.

Barrier Effect
The perceived increase in low frequency energy as you get close to a surface.

A prime signal such as composite, component-video and audio signals having its own path — not modulated onto a carrier signal or combined with other signals on a path.

Basic Remote
Controls basic functions such as volume or channel up/down and power on and off.

The lowest frequencies of the audible spectrum (approximately 20-160 Hz) characterized by low pitch. In audio, bass is subdivided into mid-bass and sub-bass regions.

Bass Extension
A measure of the lowest frequency an audio system will reproduce bass.

Bass Management
A control circuit that determines which loudspeakers receive bass signals. Additionally, a circuit which utilizes the subwoofer in a discrete 5.1-channel system to provide bass extension for the five main loudspeakers. The Bass Manager steers all frequencies below a selected frequency, such as 80Hz or lower into the subwoofer along with the LFE source signal. See LFE.

Bass Redirection
A An other term for Bass Management. See Bass Management.

Bass Reflex
A type of loudspeaker enclosure in which an aperture or port is used. The port allows internal air pressure to reinforce bass from the front of the loudspeaker.

Bass Trap
A low frequency absorber. Because of their large wavelength (up to 50 feet), low frequencies are particularly difficult to absorb. Therefore, special traps must be designed to absorb these waves, if unwanted leakage and room resonances are to be eliminated.

See Electron Beam.

A periodic variation in amplitude that results from the superposition or addition of two tones with nearly the same frequency.

Betamax. Home VCR format developed by Sony Corporation. While not the most common format still in use, BETACAM is a widely used professional video format and available in various high-resolution formats. See ED-Beta and VHS.

The frame that covers the edge of the picture tube in some TV sets.

Incorporating more than one power amplifier plus a crossover network for driving woofers and tweeters.

When things can pass in either direction through the same port or by the same path. RS-232 communications is bi-directional because the devices at either end can transmit and receive. Some switchers are bi-directional because a device connected to an input can send a signal to a device connected to an output or a device connected to an output can send a signal to a device connected to an input.

Bi-ocular Lens
A feature that improves focus in the screen corners and image brightness.

Bi-Radial Horn
A horn in which both the vertical and horizontal surfaces flare outward, though usually at different rates. Found typically used in motion picture theatre sound systems.

Connecting an amplifier to loudspeakers using separate cables for woofers and tweeters for enhance sound quality,

In electronics, bias is usually some sort of reference voltage, current or signal. In magnetic recording, a direct current (DC) or high-frequency alternating current (AC) signal which accompanies an audio signal as it is fed to a magnetic recording he

Bias Light
This light introduces an environment around the monitor, which will influence the color perception of the picture coming from the monitor. Ideally, the light should be behind the display aimed in the opposite direction of the viewer. The maximum level of light coming from any point in the background should be no more than 10 percent of the peak white level of the display device, as measured in the plane of the display device; and the background color should be neutral, the same color of gray as the gray scale of the properly calibrated monitor. The correct color of light is known as “Daylight” in the lighting industry. There are several colors that have the name Daylight attached to them. They range in color from about 5400° to 6500° Kelvin. In consumer applications, any of them will work well enough, but D6500 or 6500° Kelvin is the best choice. It is the same color of gray as is set on a correctly adjusted TV set.

Big Screen
A video display whose diagonal dimension is more than 36 inches.

The numbering system using 2 as the base. The numeric format used in representing digital information, or base-2. For example, the base-2 equivalents of 0 and 5 are 0 and 101, respectively. Each binary digit is known as a bit.

Binary Code
A coding system using the digits 0 and 1 to represent a letter, numeral or other character in a computer. For example: the character “A” in ASCII code becomes 0100 0001 in binary.

Binary Digit
Bit. 0 or 1, the smallest unit of information

Binary System
A system in which information can be expressed by combinations of the digits 0 and 1 (corresponding to "on" and "off" in computers).

Sound reproduction using two microphones usually in a “dummy head” (to emulate the shape and the response of the human hearing system) feeding a pair of headphones, so that the listener hears the sound he or she would have heard at the recording location.

Binding Post
Loudspeaker terminal that allows bare wires and/or spade terminated wire and/or a banana plug to be connect.

A type of home loudspeaker designed to improve spatial imaging through the use of two opposing drivers, both identical and operating in phase.

1) -The elementary unit of a digital signal, denoted by a value of 0 ("off") or 1 ("on"). 2) The smallest unit of information in computer systems.

Bit Rate
The number of bits per second (bps) passed by an audio or video digital carrier. Higher bit rates translate to better audio or video quality.

A method of graphic display, described in terms of pixels. A screen in which each pixel location corresponds to a unique memory location in the CPU.

The darkest visible surface, created by the absorption of all incident light and color. In video, the transmission of horizontal and vertical sync signals without picture information. In terms of displayed light, black is defined as an absence of light. Anything in the video signal that is at black or below black should not be displayed on your picture. What one sees as black is dependent on the amount of ambient light hitting the surface of the picture.

Black & White
Monochrome (one color) or luminance information. In the color television system the Black & White portion of the picture has to be one "color"; gray, D6500, 6500K (6500 degrees Kelvin) as defined by x and y values in the 1939 CIE color coordinate system.

Black Box
Generic name for electronic devices, especially signal processors.

Black Burst
The video waveform without the video elements. It includes the vertical sync, horizontal sync and the chroma burst information. Black burst is used to synchronize video equipment to align the video output. This signal is usually used for setup and to provide reference synchronization signals.

Black Burst Generator
A special device for calibrating video equipment by generating a composite video signal with a totally black picture. This black burst signal is used to synchronize video equipment together to provide vertical interval switching. It also provides black level and chroma burst information for the purpose of maintaining uniform video levels and color information

Black Level
More commonly referred to as "brightness," the black level is the level of light produced on a video screen. The level of a picture signal corresponding to the maximum limit of black peaks at which level a video screen emits no light at all (screen black). The bottom portion of the video waveform which contains the sync, blanking and control signals. The black level is set by the (incorrectly labeled) Brightness Control. See Absolute Black Level.

Black Level Control
See Brightness Control.

Black Level Retention
The ability of a monitor to maintain a constant level of black despite wide variations in average picture brightness. Poor black level retention causes blacks to become gray during dark scenes.

Black Matrix
A picture tube in which the color phosphors are surrounded by black for increased contrast.

The turning off of the electron beam that scans the image onto the screen to electronically blank part of the video signal to prevent that portion from being displayed on the screen. The test signals found in the vertical interval are examples of an area of video that should not be shown on the screen. During the interval when the beam completes a scan line it must return (retrace) back to the left. During this time, the beam must be turned off (horizontal blanking). Similarly, when the last line has been scanned at the bottom of the screen, the beam must return to the upper left. This requires vertical blanking. Sufficient control over the displayed image area should be provided in a projector to eliminate the display of any part of the vertical and horizontal interval.

Blanking Level
It is the level of a video signal which separates the range that contains the picture information from the range that contains the sync information. The level of the front and back porches. Zero IEEE units.

Most noticeable at the edges of images on a CRT, "blooming" is when the light hitting the screen is too intense and overdrives the phosphors. The edges of an image seem to exceed its boundaries. Thin lines and sharp edges may look thick and fuzzy exhibiting a loss of focus. This may be caused by the Brightness or Contrast being set too high, or by a high voltage problem which increases the raster size. When Contrast is up higher than it should be, the blooming effect causes the image to be reproduced at a larger size than dictated by the video signal. The phosphors inside the tube that produce the light can only take so much energy. If more is delivered, by turning the Contrast up to high, it will be dispersed to adjacent areas. A larger area will therefore be lit up than was intended by the video signal.

Blue "Only" Mode
In the professional video world, SMPTE Color Bars are used for adjusting the Color and Tint controls. They are switched to the "Blue Only" mode, where just the blue channel of information is displayed on screen. In the consumer world, that is usually not an option on the set. A blue filter can be used to get around that problem. Looking through it will give something close to the "Blue Only" option provided in the professional world. The blue channel is observed in setting the Color and Tint controls because the largest amount of visible change occurs in this channel for any movement of the controls. Once the blue has been set correctly, the red and green channels should also be correct, if the NTSC to RGB decoder is functioning according to the rules of the NTSC system.

Blue Enhancement
Mixes the right amount of blue information with the green signal for displaying text in a more readable "aqua" color. This color mixing affects all blue colors on the display screen (only used for TTL signals).

Blue Filter
A transparent filter that passes only the spectral color of blue. Used in conjunction with SMPTE color bars for calibrating a monitor's color and tint settings.

Blue Screen
A stationary "non-play" screen color produced by LaserDisc and DVD players.

A state of reduced resolution. See Plugged Up.

It is a cylindrical bayonet connector which operates with a twist-locking motion. Two curved grooves in the collar of the male connector are aligned with two projections on the outside of the female collar. This allows the connector to be locked in place without the need of tools. A professional type of video connector featuring a two-pin lock.

Boom Channel
Also known as the "0.1" channel. See LFE Channel.

A slang expression for excessive bass response in a recording, playback, or sound system. Also known as "muddy." A perception of the overemphasis of midbass, resulting in difficulty discerning the other frequency components of a sound as well as interfering with its imaging attributes. Excessive midbass results from standing wave effects, as well the inability to accurately reproduce very low frequencies (harmonic distortion).

The initialization process a computer goes through after power comes on. To start a new beginning, you "pull yourself by your bootstraps." Can also occur with "reset." Boundary Layer - The region in the immediate vicinity of a surface in which the phase shift between a direct and a reflected path wave is negligible within the audio frequency spectrum of interest.

The curving of scan lines in the center of the image. Bowing is a geometric distortion characterized by such curving of scan lines that should be straight.

Sound that is characterized by a pronounced aw vowel coloration, as when speaking with one's head in a box.

Bits per second.

The ability to separate audio and video signals for the purpose of switching them independently. For example: an audio and video signal from the same source may be "broken away" and switched to different destinations. This is the opposite of the term "audio follow."

The early part of the back porch portion of the video signal. The area between the horizontal sync pulse and the color burst.

Refers to excessive brightness in the character of reproduced sound which imparts a hard, crisp edge to the sound.

1) In video, usually refers to the amount, or intensity of video light produced on a screen, without regard to color. Sometimes called "black level." Brightness is a measure of the light output capability of the display device. It can be a measure of the projector's light output capability (in lumens) or the amount of light the source can provide off a given screen size and type (foot-Lamberts). The higher the number, the brighter the picture. A fixed amount of light out of a projector, say 200 lumens, will provide a particular amount of light, say 10 foot-Lamberts off a 6-foot wide screen. If the area of the 1.33:1 screen is doubled, the foot-Lamberts will drop to 5 while the lumen number will remain the same. Thus, brightness is relative to screen size. Too large a screen can significantly reduce the amount of light the source can provide since light output is constant. Light output does diminish over time in projectors, often dramatically with even typical use. Thus, smaller screen sizes are better at preserving light output long term. Typically, a 4.5- to 6-foot screen width is optimal with most projectors. Larger screen widths require a double stack projection system for optimization. All front projector and rear screen models require watching in a darkened room for best possible performance. 2) In audio, refers to an excessive amount of treble that adds a shrillness to the sound.

Brightness Control
The control on a television monitor which increases or decreases the radiance of an image and sets the visible level of the dark parts of the picture. Also called Black Level Control.

Brightness Ratio
The difference between the brightest (whitest) and darkest (blackest) areas in an image. The wider the brightness ratio, the wider the contrast ratio.

Brightness Signal
Same as the luminance (Y); a signal which carries information about the intensity at each point in the image

Broadcast Television
Conventional television broadcasting, using an antenna or satellite dish. Also refers to broadcast channels delivered via cable. Buffer - Generally referred to as a unity gain amplifier, a buffer is used to isolate the signal source from the load. A buffer can be for digital or analog signals.

In video display, a term to describe when an image has been displaying too long, resulting in a permanent "ghost" image being "burned in" to the screen phosphor. Also known as Burn.

A group of high frequency (8 to 11 cycles of 3.58 MHz) pulses that determine the phase of a color signal. Also called "color burst." Needed to synchronize phase of 3.58 MHz oscillator in receiver to correct hues in C signal. The hue of color sync phase is yellow-green.