Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!olivea!oliveb!felix!daemon From: daemon@felix.UUCP (The devil himself) Newsgroups: comp.compression Subject: Re: Compression of 16-bit sound files Summary: DPCM compression for sound Keywords: DPCM sound compression Message-ID: <161069@felix.UUCP> Date: 15 Apr 91 14:56:28 GMT References: Reply-To: peterg@felix.UUCP (Peter Gruenbeck) Organization: FileNet Corp., Costa Mesa, CA Lines: 26 In article rog@speech.kth.se (Roger Lindell) writes: >Hello, > >I would like to know if there exists any good and moderately fast compression >programs that will compress 16-bit soundfiles by a large amount. From: peterg@felix.UUCP (Peter Gruenbeck) I did some electronics tinkering about 10 years ago with an OKI semiconductor chip set for digitial sound capture and synthesis. It was essentially an A/D converter and digital signal processor which compressed the sounds on the fly using a method called ADPCM. ADPCM which stands for Adaptive Differential Pulse Code Modulation basically coded each sound sample as a 3 or 4 bit difference (+-4 or +-8 amplitude levels) from the previous sample. This is based on the assumption that the sounds being recorded (speech & music) are more or less continuous. This technology is now widely available in digital telephone answering machines. Using this method, 15 seconds of speech at an 8K sample rate can be compressed into about 64KB of memory. -- Pete Gruenbeck -- The poor grammar, spelling errors, and errors o o in usage are included with a purpose: I write ^ something for everybody. (---)