Abstract: A dual format optical disc (10) on which a musical selection is recorded in two different formats, such as CD and DVD. For example, standard 2-channel rendition of the selection can be stored CD format and a 5.1 channel rendition of the same selection can be recorded using a DVD format. The disc can be used in standard CD player with a provided spacer (44) arranged and constructed to allow the player's head (42) to read the CD information. The disc can also be played with a DVD player in which case the spacer (44) may be removed. Alternatively the disc can be formed with an integral disc, in which case, a DVD player includes an adjusting member to adjust reading head (40) of the player to read either a standard DVD disc or the inventive disc.

Abstract: A system for testing compact discs having audio or video information and time subcode information indicating the elapsed time from the beginning of the audio, video or data information thereon in which three microprocessors respectively monitor the HF signal, the radial tracking signal and the decoder digital flags produced by a CD player to produce error signals indicating HF dropout, HF low, modulation amplitude, radial tracking, Burst, Bler, and uncorrectable errors and in which a computer having a memory responds to the time signal produced by the player periodically to transfer the contents of the microprocessors to the memory together with the time of transfer and to reset the microprocessors, thus to record errors and to locate the positions thereof on the disc in terms of the time subcode information. Initially an eccentricity test is performed and the entire test is stopped if the eccentricity is excessive. The computer is programmed to display the test results in various formats.