Digital media players are a widely used form of audio reproduction. In the home, players that play CDs (compact discs) are widely used, and more recently DVD (digital versatile disc) players capable of playing CDs serve the joint function of video and audio playback. Portable audio disc players are also used by many persons on a regular basis. The disc players typically play CDs (compact discs) or MDs (mini discs). Digital audio tape (DAT) players exist, but are used less frequently. The CD format is currently the most popular digital audio format.
A pre-recorded CD or MD contains control code information concerning the audio tracks recorded onto it. The control code information is recorded on channels separate from the main audio channels. Control code information includes Table of Contents (TOC) information. The TOC is recorded at the beginning of the disc in a lead-in area. TOC data is also known as mode 1 of a “Q” channel. TOC information includes: number of tracks, absolute starting time of each track, track number, index numbers within a track, time within a track, and absolute time. Other control code information is recorded in a “P” code channel. The P channel contains a flag bit that designates the start of a track. The length of a start flag is a minimum of two seconds, but equals the pause length between two tracks if this length exceeds two seconds. More generally, digital audio media of any form can be expected to have control code information concerning, at least, track starting locations.
USPTO Backgrounds
USPTO Backgrounds