Xref: utzoo comp.compression:418 alt.comp.compression:217 Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!cornell!rochester!pt.cs.cmu.edu!o.gp.cs.cmu.edu!fs7.ece.cmu.edu!fs7.ece.cmu.edu!abl From: abl@thevenin.ece.cmu.edu (Antonio Leal) Newsgroups: comp.compression,alt.comp.compression Subject: Re: Compression of 16-bit sound files. Message-ID: Date: 21 Apr 91 08:35:44 GMT References: <1991Apr17.140822.23647@thebox.rain.com> <1991Apr21.002203.4414@nntp-server.caltech.edu> <1991Apr21.020231.8109@bmerh408.bnr.ca> Sender: news@fs7.ece.cmu.edu (USENET News System) Organization: Electrical and Computer Engineering, Carnegie Mellon Lines: 39 In-Reply-To: myhui@bnr.ca's message of 21 Apr 91 02:02:31 GMT myhui@bnr.ca (Michael Hui) writes: > >In article <1991Apr21.002203.4414@nntp-server.caltech.edu> madler@nntp-server.caltech.edu (Mark Adler) writes: >[...] >>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. > >I wonder why no compression was used? Certainly the IC technology at that time >was advanced enough to have made it a cheap proposition. The FIR (I guess...) >filters used to interpolate between samples in most CD players must take up at >least as much silicon as a delta-modulation decoder. Let's go easy here. These are distinct issues: 1 - Use of delta modulation - the converter is _much_ cheaper than the 16-bit D/As, which are finicky as hell. But, unless you jack up the data rate to equivalent levels, it's a lossy compression - transients may get it in the neck. Never mind honest audio engineer objections, can you imagine what the baboons in the mystic audio business would have made of it ? We got enough of a circus with a bullet-proof PCM scheme as it was ... 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). 2 - Lossless compression, e.g. Huffmann or LZW. Even assuming that compression and error-correction didn't get on each other's hair, can you say "enough memory and computational power to decode a data stream at 2*16*44.1 kbit/s" ? Probably this should move over to rec.audio ... -- Antonio B. Leal Dept. of Electrical and Computer Engineering Bell: [412] 268-2937 Carnegie Mellon University Net: abl@ece.cmu.edu Pittsburgh, PA. 15213 U.S.A.