Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!uunet!mcsun!hp4nl!sci.kun.nl!ge From: ge@dbf.kun.nl (Ge' Weijers) Newsgroups: comp.compression Subject: Re: Compression of 16-bit sound files. Message-ID: <3094@wn1.sci.kun.nl> Date: 23 Apr 91 13:00:22 GMT Article-I.D.: wn1.3094 References: <1991Apr17.140822.23647@thebox.rain.com> <1991Apr21.002203.4414@nntp-server.caltech.edu> <1991Apr21.020231.8109@bmerh408.bnr.ca> Sender: root@sci.kun.nl Followup-To: comp.compression Lines: 21 abl@thevenin.ece.cmu.edu (Antonio Leal) writes: > Incidentally, the "1-bit converter" business is delta mod. Do some > manipulation on the 16 bit samples, and feed a delta converter at a > rate high enough to sound good. Sell as a major improvement (well, > it _is_ guaranteed to be monotonic, which 16-bit ADCs should, but > may not, be). The "Do some manipulation" makes the result less than perfectly monotonic. A straightforward implementation of deltamodulation would need a terribly high sampling frequency (2^16 * 44 kHz) so the digital data is preprocessed, and this process adds noise. Care is taken to put most of the noise above the 22kHz by a process called 'noise shaping'. I don't know how that works, as the publications I've seen are less than clear. Ge' -- Ge' Weijers Internet/UUCP: ge@cs.kun.nl Faculty of Mathematics and Computer Science, (uunet.uu.net!cs.kun.nl!ge) University of Nijmegen, Toernooiveld 1 6525 ED Nijmegen, the Netherlands tel. +3180652483 (UTC-2)