B Terms

B-ISDN: Broadband Integrated Services Digital Network

B-picture: Biderectiaonally Predictive-coded Picture. An MPEG term for a picture that is coded using motion compensated prediction from a past and/or future reference picture.

Back Coating: Layer on the back side of a recording tape that is designed to aid in transport through the recorder and reduce print-through.

Background: One of the video sources involved in keying. Specifically, the background video is the signal which has portions of it replaced with the key (or foreground) signal. Using chroma key as an example in a weathercast, the background is the weather map and the foreground is the weathercaster. The foreground signal is often referred to as cutting a "hole" in the background video signal.

Backward Compatibility: A new coding standard, or tape format is backward compaitble with and existing coding standard if existing decoders (designed to operate with the existing coding standard) are able to continue to operate by decoding all or part of the bitstream produced according to the new standard. In the case of video tape machines, the new machine will play back recordings made on teh older format machine.

Backward Motion Vector: A motion vector that is used for motion compensation from a reference picture at a later time in display order.

Band: A portion of the frequency spectrum covering a specified range of frequency.

Bandwidth: The range between the lowest and highest frequencies used to transmit a signal from one site to another. Bandwidth is a term that is used in analog application but it is sometimes used interchangeably with bit rate.

Barcode: Method of tape data identification used in several LMSª application programs. Barcode labels are prepared external to the LMS and affixed to the spine of the cassette. The barcode can be read by an external barcode reader; or in the multi-cassette system by an optical sensor mounted within the cassette elevator. Barcodes are also used in multimedia educational applications using laserdisc players.

Base: The primary constituent of recording tape that carries the magnetic coating.

Baseband: Signal frequencies before they are modulated by the radio frequency carrier.

Baud: A unit of transmission speed to describe the the rate at which binary data is communicated, one baud is approximately equal to one bit per second.

BER: Bit Error Rate. The ratio of received bits that are in error relative to the total number of bits received. It is used as a measure of noise induced distortion in a digital bit stream. BER is expressed as a power of ten. For example a 1 bit error in 1 million (10 to the 6th power) bits is a BER of 10-6.

Bernoulli Devices: A medium-high-capacity, disk-storage medium used for digital data storage. Bernoulli disks use a floppy piece of magnetic material housed in a rigid cassette. The disks have a storage capacity of about 20 MB and a data-access performance equivalent to hard drives.

Betacam: Component analog video tape recording format.

Betacam SP: Enhanced performance Betacam using higher carrier frequencies and metal particle tape.

Betacam SX: A compressed digital component recording format.

Bi-Directional Microphone: A microphone that is sensitive to sounds from only two directions.

Bias: A constant signal mixed with the signal to be recorded and sent to the record head to improve the process of recording. It helps to achieve a better level of saturation on the tapeÕs magnetic particles.

Bias Trap: Used to prevent the bias signal or multiples of this signal, called harmonics, from entering the sound path. (See Bias).

Binary: Used to prevent the bias signal or multiples of this signal, called harmonics, from entering the sound path. (See Bias).

Bit: (1) An abbreviation of the words "binary digit", the smallest unit of information (usually 1 or 0). (2) A single pulse in a group of pulses. (3) A unit measure of the information capacity of a storage device.

Bitmap: A representation of images or graphic information that is made up of individual bits of picture information or pixels (picture elements). Bitmaps are computer maps of these bits which can be re-created pixel for pixel when displayed or printed.

Bitmapped Graphics: A form of graphics that is made up of individual bits of picture information or pixels (picture elements). The graphic consists of a computer map of these bits which is re-created pixel for pixel when displayed or printed.

Bit Rate: The digital equivalent of bandwidth, bit rate is measured in bits per second. It is used to express the rate at which the compressed bitstream is transmitted. The higher the bit rate, the more information that can be carried.

Bits per Pixel: The number of bits used to represent the color value of each pixel in a digitized image.

Black: Video signal set to a pre-determined level (7.5 IRE units) so that no picture information appears and the screen is black. Also referred to as pedestal or setup, the level at which this signal is set determines overall picture contrast and quality.

Black Level: In an NTSC composite signal, 7.5 IRE units is the lowest point in the signal that luminance components are permitted. Luminance information falling below this point is cut off and lost.

Blanking: Suppression of the video scanning beam: the period of time that the scanning beam is shut off. During raster scanning, the beam must be shut off for retrace to position the beam for the next scan line or field.

Blanking Signal: The pulses added to the video signal to indicate that the scanning beam should be shut off for the period of retrace time.

Block: An 8-row by 8-colume orthogonal array of pixels. Block size may vary by compression scheme.

Border: In switcher terminology, a thickened edging, similar to a picture frame, placed around a key signal, a digital effect, or the edges of a wipe pattern. Typically, the thickness, softness, and color of the border are completely adjustable.

BPG: Business and Professional Group.

Bps: Bytes per second.

bps: Bits per second.

Branch: A term used in interactive media programming which refers to the directions the program may take based on user responses. A branch is a program segment linked to other segments by decisions the program viewer makes.

Breakup: A momentary image distortion caused by the loss of sync.

Bridge: An electronic device which mixes or switches the signals from three or more locations for audio or video teleconferencing.

Bridging Switcher: A video switcher often used in CCTV security applications which contains two video outputs. Normally, one output is dedicated for sequential viewing of the cameras while the other allows manual call-up of any desired camera.

Broadcast System: A system which allows public access to electronically-transmitted information. Typically, a commercial television or radio station regulated by the Federal Communications Commission (FCC).

Broadband: A general term used to describe wide bandwidth equipment or systems which can carry a large proportion of the electormagnetic spectrum. A broadband communications system can deliver multiple channels and other services.

Burn, Burn In: Overly bright images that are permanently retained on the surface of a television camera pick-up tube. Burns look like permanent blackened spots or smudges on the picture surface. CCD imagers do not exhibit this phenomena.

Bus: A means by which one input can be selected from among several different inputs. The output of the bus is then sent to a specific destination, either internal or external to the switcher. A minimum of two buses are required to perform a simple mix, wipe, or key operation.

1.) A conductor or group of conductors which provides an electronic pathway between two or more devices.

2.) In data communication, a network in which stations are arranged along a linear medium (e.g. a length of cable).

3.) In computer architecture, a path over which information travels internally among various components of a system.

Byte: Traditionally defined as a sequence of 8-bits. Sometimes extended to mean 10-bit or 12-bit words.