Audio/Video Glossary

UDF (Universal Disk Format): An international standard defining the file and directory structures for optical media (such as CD-ROM and DVD). Developed by the Optical Storage Technology Association (OSTA), UDF has several advantages over the ISO 9660 file system used by standard CD-ROMs. It was designed for read-write interoperability between all the major computer operating systems as well as compatibility between rewritable and write-once media. The standard allows for efficient recording of small packages of data, using incremental packet writing.
UNDERSCAN: The opposite of overscan. In underscan, a video or computer image is reduced so that all four edges are visible on-screen, leaving it surrounded by black borders. Underscan is used to show what is happening in the blanking period and at the beginning and end of scan lines and frames. Underscanning can uncover latent image problems for identification and correction.
UPC (Universal Product Code): A unique thirteen-digit inventory tracking number assigned to a compact disc by the Uniform Code Council to allow tracking when sold commercially. The number is written in the disc’s Table of Contents. The European equivalent is known as the EAN.
UV22: A proprietary process developed by Apogee Electronics, similar in concept to dither, that adds a high-frequency, narrowband signal just below half the digital sampling frequency (Nyquist frequency): around 22kHz for 44.1kHz systems such as DAT and CD.

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