OEM
Original equipment manufacturer. Computer maker.

One_Random_PGC Title
In DVD-Video, a Title within a Video Title Set (VTS) that contains a single Program Chain (PGC), but does not meet the requirements of a One_Sequential_PGC Title. Contrast with to One_Sequential_PGC Title and Multi_PGC Title.

One_Sequential_PGC Title
In DVD-Video, a Title within a Video Title Set (VTS) that contains a single Program Chain (PGC) with the following attributes: 1) PG Playback mode is Sequential, 2) no Next PGC, Previous PGC or Go Up PGCs are defined, and 3) the Navigation Timer is neither set, nor referred to. Contrast with One_Random_PGC Title and Multi_PGC Title.

operating system
The primary software in a computer, containing general instructions for managing applications, communications, input/output, memory and other low-level tasks. DOS, Windows, Mac OS, and UNIX are examples of operating systems.

Opposite Track Path (OTP)
Dual-layer disc where Layer 0 and Layer 1 have opposite track directions. Layer 0 reads from the inside to the outside of the disc, whereas Layer 1 reads from the outside to the inside. The disc always spins clockwise, regardless of track structure or layers. This mode facilitates movie playback by allowing seamless (or near-seamless) transition from one layer to another. In computer applications (DVD-ROM), it usually makes more sense to use the Parallel Track Path (PTP) format where random access time is more important.

Orange Book
The document begun in 1990 which specifies the format of recordable CD. Three parts define magneto-optical erasable (MO) and write-once (WO), dye-sublimation write-once (CD-R), and phase-change rewritable (CD-RW) discs. Orange Book added multisession capabilities to the CD-ROM XA format.

OS
Operating system.

OSTA
Optical Storage Technology Association (seehttp://www.osta.org).

OTP
See Opposite Track Path.

out of band
In a place not normally accessible.

Outer diameter
Width of the disc. This is 12 cm for "normal" CDs and DVDs, and 8 cm for small CDs and DVDs.

overscan
The area at the edges of a television tube that is covered to hide possible video distortion. Overscan typically covers about 4 or 5 percent of the picture.