U.S. Philips Corporation

Johannes Petrus Sinjou

Herman G Lakerveld

Gerard E Van Rosmalen

Kornelis Bulthius

A method and apparatus for recording and reading information in the form of a track of pit and land areas on an optical digital disc record carrier. The information is first encoded from symbol blocks of data bits into symbol blocks of channel bits to which are added merging bits selected so as to minimize the d.c. unbalance or digital sum value of the channel bits. Those parts of the stream of channel bits for which the d.c. unbalance does not meet predetermined criteria are subjected to selective scrambling to correct such unbalance prior to recording. During read-out the correctively scrambled parts of the recovered symbol blocks of data bits are descrambled in an inverse manner. Information identifying such parts is recorded with the channel bits. The invention also relates to a record carrier on which information has been so recorded.

Digital sum value corrective scrambling in the compact digital disc

A playing apparatus, more specifically a video player for playing round records with a central hole, which are made of a transparent material, which records at one side have a transparent surface and at their other side are provided with information tracks which are optically readable with the aid of a read beam, which tracks are covered by a light-reflecting layer. In order to enable both relatively thick rigid records and relatively thin flexible records to be played on one playing apparatus, the invention provides a transparent adapter disc, which together with a flexible record can be positioned on the playing apparatus and driven in a rotary fashion. In order to prevent dust particles from being trapped between the flexible record and the transparent adapter disc, the adapter disc may be provided with a central recess with a number of air admission apertures at the circumference thereof, so that during operation a thin film of air is formed between the flexible record and the adapter disc.

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Eindhoven, Netherlands

Johannes Petrus Sinjou