jgc (07/29/82)
The Philips "Compact Disc" System Explained (one L in Philips, you guys) Philips has announced that their "Compact Disc" system will be launched in Europe in January 1983. Two versions of the player will be marketed, a top-loader and a front load "HiFi Component" style. The players will be priced at around 1700 guilders. About 200 record titles will be available from PolyGram and Philips. About 20 Japanese and European firms showed their version of a CD player at the CES in Chicago. It is expected that Sony will release their player(s) in Japan at the same time Philips starts selling units in Europe. As of May 1982 30 companies have been licensed to produce players (Sony, Matsushita, Toshiba, Pioneer, Revox, Marantz ...) and eight more have been licensed to produce records (Toshiba EMI, CBS/Sony, Nippon Columbia...). No American recording firms have yet been licensed to produce records. The Compact Disc standard uses a single sided 12 cm. disc to record up to one hour of sound on two independent tracks. It has no grooves, the digitally encoded recording lies beneath the disc surface, invulnerable to dirt and damage. The recording is read using a non-contacting solid-state laser. The specs on the system are : frequency resp. 20 Hz - 20 kHz dynamic range >90db S/N Ratio >90db (~97db) channel sep. >90db harmonic dist. <0.01% wow and flutter none The system is based on 16-bit linear PCM with a sample rate of 44.1 kHz. A Cross Interleave Reed-Solomon Code is used for error correction. This code can correct a drop-out of up to about 3500 successive bits, which corresponds to a track length of about 3.5mm. The system can also compensate with interpolation for errors up to about 12000 bits. The modulation scheme in use is called Eight-to-Fourteen Modulation (EFM). More technical details are available from a paper : VRIES et al "The Compact Disc Digital Audio System - Modulation and Error Correction", 67th AES Conv., No. 1674(H-8), October 1980. The Philips players use seven VLSI chips to decode the serial data stream (4.3218 Mbits/s) into 2 channels of analog audio. One interesting techniques used is digital oversampling. This increases the S/N ratio and enables the use of a fairly simple output low pass filter. jim constantine philips labs