Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site allegra.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!jay From: jay@allegra.UUCP (Jay Hyman) Newsgroups: net.audio Subject: CD Players - What's inside? Message-ID: <4720@allegra.UUCP> Date: Mon, 15-Jul-85 10:04:20 EDT Article-I.D.: allegra.4720 Posted: Mon Jul 15 10:04:20 1985 Date-Received: Wed, 17-Jul-85 05:13:11 EDT Reply-To: jay@allegra.UUCP (Jay Hyman) Organization: AT&T Bell Laboratories, Murray Hill Lines: 36 The February, 1985 issue of Communications Magazine (IEEE) had a cover story on the communications aspects of the CD player which I have found very helpful. (Now I know what "oversampling" means in this context, etc.) The piece was written by Hans Peek from Philips, and describes the CIRC error coding scheme in detail. While it seems to be pretty robust, he suggests two possible improvements to the error correction systems: "multiple-level reliability information (that is, distinction in flag qualities such as certainly in error, and less probable (sic) in error)... may be provided in future generations of CD players." And in interpolating missing samples, while linear interpolation is described as the current technique, "restoration is always possible by using adaptive interpolation... Although adaptive interpolating is not used in current players, it is a future possiblility." In the D/A section, he describes the use of 4x oversampling with 14-bit converters (he doesn't specify one or two.) My question is this: given that the differences between CD players are said to be in their error-correcting capabilities, what do the more expensive ones do? Are there CD players on the market now that already use these "next generation" techniques, or do they do other things differently (and what) ? Do any players use straight 16-bit converters with analog filters? More generally, do the things explained here characterize all CD players on the market, or just one particular Philips model? And one less technical question: the Philips player pictured on the cover looks exactly like the Magnavox model 1040 a friend of mine just got for about $200. Are they identical, or just packaged in the same housing? Jay Hyman allegra!jay