Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site brl-tgr.ARPA Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!genrad!teddy!panda!talcott!harvard!seismo!brl-tgr!ron From: ron@brl-tgr.ARPA (Ron Natalie) Newsgroups: net.audio Subject: Re: CD Reflections Message-ID: <7441@brl-tgr.ARPA> Date: Wed, 16-Jan-85 19:53:30 EST Article-I.D.: brl-tgr.7441 Posted: Wed Jan 16 19:53:30 1985 Date-Received: Sun, 20-Jan-85 05:26:00 EST References: <15100001@hpfcmp.UUCP> <3411@mit-eddie.UUCP> <1420@hplabs.UUCP> Organization: Ballistic Research Lab Lines: 20 > > It seems to me that the disc itself was created with a given sampling rate. > How can a player change this? > Sampling has a funny definition here. They mean number of numbers output by the DtoA per second. The problem is that the D to A transits from one number directly to another number. This sharp transition generates all kinds of higher frequencies which must be filtered out (as a result of this 44kHz square wave you've just created). You have to be really careful with your filter to get rid of the things that are a result of the transition without mucking up the encoded signal. So, lets interpolate and generate three intermediate steps in between each of the original samples. Now the step transitions are generating 176 kHz squarewaves, and you can be a little sloppier with your filter because rather than being 22kHz above the real signal you are 154 kHz above it. You are infact doing some of the low pass filtering in the digital domain because it's easier (i.e. cheaper) to build that way. -Ron