Backward compatibility
The ability of a new coding standard to be handled by existing decoders.

Backward motion vector
A motion vector used for motion compensation from a reference picture that occurs later in display order.

Bandwidth
The range of signal frequencies that a piece of audio or video equipment can encode or decode; the difference between the limiting frequencies of a continuous frequency band. Video uses higher frequency than audio, thus requires a wider bandwidth.

BAUD
Pronounced bawd, the number of signaling elements that occur each second. The term is named after J.M.E. Baudot, the inventor of the Baudot telegraph code.

At higher speeds, it is possible to encode more than one bit in each electrical change. 4,800 baud may allow 9,600 bits to be sent each second. At high data transfer speeds, therefore, data transmission rates are usually expressed in bits per second (bps) rather than baud. For example, a 9,600 bps modem may operate at only 2,400 baud.

Betacam
A half-inch video recording format developed by Sony that offers near one-inch tape quality on a portable system.

Bit depth
The number of bits used to describe the color of each pixel on a computer display. For example, a bit depth of two means that the monitor can display only black and white pixels; a bit depth of four means the monitor can display 16 different colors; a bit depth of eight allows for 256 colors; and so on.

Bi-linear filtering
When a small texture is used as a texture map on a large polygon, a stretching will occur and large blocky pixels will appear. Bi-linear filtering smoothens out this blockiness by applying a blur.

Bitrate
The rate at which a storage medium delivers a compressed bitstream to a decoder's input.

Blank or blanking interval
A period in which no video signal is received by a monitor, while the videodisc or digital video player searches for the next video segment or frame to display.

BLINDMATE SINGLE-CONNECTOR ATTACHEMENT (SCA)
All disk power, I/O and configuration connections have been incorporated within an 89-pin single connector that supports both 8-bit and 16-bit parallel SCSI with Single-Ended or Differential options. This eliminates changes to connector configuration when performance requirements change.

Block
An 8-row by 8-column matrix of pels, or 64 discrete cosine transform coefficients (source, quantized or dequantized).

Bottom field
One of two fields that comprise a frame of interlaced video. The lines of the top and bottom fields alternate on a screen, so that each line of a bottom field is located immediately below the corresponding line of the top field.

Bps
Abbreviation of bits per second, the standard measure of data transmission speeds.

Broadcast quality
In the US, a standard of 525 lines of video picture information at a rate of 60 Hz. See NTSC format.

BUS

• A collection of wires through which data is transmitted from one part of a computer to another. You can think of a bus as a highway on which data travels within a computer. When used in reference to personal computers, the term bus usually refers to internal bus. This is a bus that connects all the internal computer components to the CPU and main memory. There's also an expansion bus that enables expansion boards to access the CPU and memory. All buses consist of two parts – an address bus and a data bus. The data bus transfers actual data whereas the address bus transfers information about where the data should go. The size of a bus, known as its width, is important because it determines how much data can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, whereas a 32-bit bus can transmit 32 bits of data. Every bus has a clock speed measured in MHz. A fast bus allows data to be transferred faster, which makes applications run faster. On PCs, the old ISA bus is being replaced by faster buses such as PCI. Nearly all PCs made today include a local bus for data that requires especially fast transfer speeds, such as video data. The local bus is a high-speed pathway that connects directly to the processor. Several different types of buses are used on Apple Macintosh computers. Older Macs use a bus called NuBus, but newer ones use PCI.
• In networking, a bus is a central cable that connects all devices on a local-area network (LAN). It is also called the backbone.

BUS MASTERING
Refers to a feature supported by some bus architectures that enables a controller connected to the bus to communicate directly with other devices on the bus without going through the CPU. Most modern bus architectures, including PCI, support bus mastering because it improves performance.

Byte aligned
A bit in a coded bitstream that is located a multiple of 8 bits from the first bit in the stream.