Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: Notesfiles $Revision: 1.6.2.17 $; site uiucdcsb.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!ihnp4!inuxc!pur-ee!uiucdcsb!emrath From: emrath@uiucdcsb.UUCP Newsgroups: net.audio Subject: Re: Sheffield CDs and why they sound bad Message-ID: <5700063@uiucdcsb.UUCP> Date: Fri, 12-Oct-84 04:26:00 EDT Article-I.D.: uiucdcsb.5700063 Posted: Fri Oct 12 04:26:00 1984 Date-Received: Sun, 14-Oct-84 07:03:52 EDT References: <460@watdcsu.UUCP> Lines: 31 Nf-ID: #R:watdcsu:-46000:uiucdcsb:5700063:000:1625 Nf-From: uiucdcsb!emrath Oct 12 03:26:00 1984 Regarding Shaun's point about compression: It sounds like what you are saying is that a CD could be made where the data is 16 bit samples, but every so often a control sample is read which (digitally) controls the gain of the analog (de)amplifier used on the output of a 16-bit D/A. Assuming you could make the original recording using a 20 or 24 bit A/D (maybe someday), the samples could be converted to 16 bits by shifting small ones left and setting the control words to decrease the gain of the playback amplifier by 6dB for each bit the following samples are left shifted. Naturally, the 20 -> 16 bit conversion looks ahead to make sure that no MSBs are lost, only the LSBs of numerically large samples. The recorded signal is compressed, and proper playback entails downward expansion. It would probably sound bad without proper playback. One possible problem with this may be the inability to switch the gain of the PB amp fast enough and at the exact times, thus causing distortion and noise. (also, as you pointed out, its of dubious value) Any way, the whole idea raises the following question. Do current CDs have data format version information stored on the disk, allowing future format changes? (they must, I suspect) A drastic change, such as the one above, might mean that version n players would reject version n+1 disks, but a version n+1 player should be able to play any disk of version 1..n+1. Recalls the evolution of the cassette, with CrO2, Dolby B, Dolby C, dbx, Metal.... Perry Emrath ...pur-ee!uiucdcs!emrath DCS, U of IL emrath%uiuc@csnet-relay.arpa "Life is a bitch, and then you die"