Track (optical disc) Track (optical disc) On an optical disc, a track (CD) or title (DVD) is a subdivision of its content. Specifically, it is a consecutive set of "sectors" (called "timecode frames" on audio tracks) on the disc containing a block of data. One "session" may contain one or more tracks of the same or different types. There are several kinds of tracks, and there is also a sub-track index for finding points within a track. Blu-ray discs can also be written in a sequential, session based mode modelled on CD and DVD. A Blu-ray "track" refer to the entire physical storage
Picture disc unhappy with their quality and soon began making an improved type. A rigid blank shellac core disc was sandwiched between two illustrated sheets and each side was then topped with a substantial layer of high-quality clear plastic into which the recording was pressed. Like nearly all records being made for the general public, they were recorded at 78 rpm, but one issue was recorded at 33⅓ rpm, a speed already in use for special purposes which Victor was then unsuccessfully attempting to introduce into home use. It was the first 33⅓ rpm picture disc and the only one made until