B
B picture (or B frame)- One of three picture types used in MPEG video. B pictures are bidirectionally predicted, based on both previous and following pictures. B pictures usually use the least number of bits. B pictures do not propagate coding errors since they are not used as a reference by other pictures.
bandwidth- Strictly speaking, the range of frequencies (or the difference between the highest and the lowest frequency) carried by a circuit or signal. Loosely speaking, the amount of information carried in a signal. Technically, bandwidth does not apply to digital information; the term data rate is more accurate.
BCA- Burst cutting area. A circular section near the center of a DVD disc where ID codes and manufacturing information can be inscribed in bar-code format.
Bidirectional prediction- A form of compression in which the codec uses information not only from frames that have already been decompressed, but also from frames yet to come. The codec looks in two directions: ahead as well as back. This helps avoid large spikes in data rate caused by scene changes or fast movement, improving image quality.
birefringence- An optical phenomenon where light is transmitted at slightly different speeds depending on the angle of incidence. Also light scattering due to different refractions created by impurities, defects, or stresses within the media substrate.
bit rate- The volume of data measured in bits over time. Equivalent to data rate.
bit- A binary digit. The smallest representation of digital data: zero/one, off/on, no/yes. Eight bits make one byte.
bitmap- An image made of a two-dimensional grid of pixels. Each frame of digital video can be considered a bitmap, although some color information is usually shared by more than one pixel.
bits per pixel- The number of bits used to represent the color or intensity of each pixel in a bitmap. One bit allows only two values (black and white), two bits allows four values, and so on. Also called color depth or bit depth.
bitstream recorder- A device capable of recording a stream of digital data but not necessarily able to process the data.
bitstream- Digital data, usually encoded, designed to be processed sequentially and continuously.
BLER- Block error rate. A measure of the average number of raw channel errors when reading or writing a disc.
block- In video encoding, an 8x8 matrix of pixels or DCT values representing a small chunk of luma or chroma. In DVD MPEG-2 video, a macroblock is made up of 6 blocks: 4 luma and 2 chroma.
blocking- A term referring to the occasional blocky appearance of compressed video (an artifact). Caused when the compression ratio is high enough that the averaging of pixels in 8x8 blocks becomes visible.
Blue Book- The document that specifies the CD Extra interactive music CD format (see also Enhanced CD). The original CDV specification was also in a blue book.
Book A- The document specifying the DVD physical format (DVD-ROM). Finalized in August 1996.
Book B- The document specifying the DVD-Video format. Mostly finalized in August 1996.
Book C- The document specifying the DVD-Audio format.
Book D- The document specifying the DVD record-once format (DVD-R). Finalized in August 1997.
Book E- The document specifying the rewritable DVD format (DVD-RAM). Finalized in August 1997.
bps- Bits per second. A unit of data rate.
brightness- Defined by the CIE as the attribute of a visual sensation according to which area appears to emit more or less light. Loosely, the intensity of an image or pixel, independent of color; that is, its value along the axis from black to white.
buffer- Temporary storage space in the memory of a device. Helps smooth data flow.
burst- A short segment of the color subcarrier in a composite signal, inserted to help the composite video decoder regenerate the color subcarrier.
button number- These are consecutive numbers assigned to each button on a menu, ranging from `1' to `36'.
button- This is a rectangular area in the Sub-picture display area highlighted by the Highlight Information (HLI) that is used to define the active area on a menu associated with a specific action.
B-Y, R-Y- The general term for color-difference video signals carrying blue and red color information, where the brightness (Y) has been subtracted from the blue and red RGB signals to create B-Y and R-Y color-difference signals.
byte- A unit of data or data storage space consisting of eight bits, commonly representing a single character. Digital data storage is usually measured in bytes, kilobytes, megabytes, and so on.
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