Xref: utzoo comp.compression:425 alt.comp.compression:223 Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!jarthur!nntp-server.caltech.edu!madler From: madler@nntp-server.caltech.edu (Mark Adler) Newsgroups: comp.compression,alt.comp.compression Subject: Re: Compression of 16-bit sound files. Message-ID: <1991Apr21.185611.8680@nntp-server.caltech.edu> Date: 21 Apr 91 18:56:11 GMT References: <1991Apr21.002203.4414@nntp-server.caltech.edu> <1991Apr21.163913.2249@smsc.sony.com> Organization: California Institute of Technology, Pasadena Lines: 21 In article <1991Apr21.163913.2249@smsc.sony.com> dce@smsc.sony.com (David Elliott) writes: >In article <1991Apr21.002203.4414@nntp-server.caltech.edu> madler@nntp-server.caltech.edu (Mark Adler) writes: >>However, they could have done a lossless compression, using differential >>methods, and gotten about twice the time (well over two hours) on a CD. > >Are you sure about that? Can you do lossless compression of sound in >general with differential methods? How do you handle big zero-crossings >of fairly high-frequency square-ish waves efficiently? I'm sure that you can get about 2:1 compression losslessly on the average. It would vary with the source material, of course. There is no way to get 2:1 all the time, over short pieces of sound. But some regions will be less, some more. CD players can already handle some buffering to vary the rate of data of the disk to attain an exactly constant rate to the D/A converters. Come the think of it, this may explain why it wasn't done--it would require more ram in the decoder. As was pointed out, the processing requirements for decompression would be minimal. But the buffering may not be. Mark Adler madler@pooh.caltech.edu