Xref: utzoo comp.compression:410 alt.comp.compression:215 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: <1991Apr21.002203.4414@nntp-server.caltech.edu> Date: 21 Apr 91 00:22:03 GMT References: <1991Apr11.141742.13069@mintaka.lcs.mit.edu> <1991Apr17.140822.23647@thebox.rain.com> Organization: California Institute of Technology, Pasadena Lines: 23 Jon W{tte (no, your modem is fine--it's a brace) writes: >> I'm quite sure that CDs use a standard, "straight" storage method. >> Itherwise you wold lose about the one advantage that CDs have over >> LPs, sound-wise: good response to transients (spikes) and other >> high-energy, high-frequency sound. Yes, they store 16-bit samples (one per channel) with no compression. However, they could have done a lossless compression, using differential methods, and gotten about twice the time (well over two hours) on a CD. >> No, CDs aren+t compressed. Rather, they're expanded for error >> correction (added redundancy) If this is Hamming codes or some >> sort of parity / checksum / CRCs, I do not know. They use Reed-Solomon codes. As I recall, it is a 3/4 rate (which means one-fourth of the bits are for error-correction) 6-bit symbol code, with some amount of interleaving. These codes have excellent burst correction capabilities, so macroscopic scratches in the CD result in no loss of data. Mark Adler madler@pooh.caltech.edu