From dctranth@unity.ncsu.edu Wed Jan 12 20:40:46 2000 Received: from eos01mh.eos.ncsu.edu (eos01mh.eos.ncsu.edu [152.1.9.16]) by uni02mh.unity.ncsu.edu (8.8.7/8.8.7) with ESMTP id UAA22432 for ; Wed, 12 Jan 2000 20:40:45 -0500 (EST) Received: from stamp.math.ncsu.edu (stamp.math.ncsu.edu [152.1.30.228]) by eos01mh.eos.ncsu.edu (8.8.7/8.8.7) with ESMTP id UAA29025 for ; Wed, 12 Jan 2000 20:40:45 -0500 (EST) Received: from uni02du.unity.ncsu.edu (uni02du.unity.ncsu.edu [152.1.2.66]) by stamp.math.ncsu.edu (8.9.2/8.9.2) with ESMTP id UAA19664 for ; Wed, 12 Jan 2000 20:40:45 -0500 (EST) Received: (from dctranth@localhost) by uni02du.unity.ncsu.edu (8.8.4/EC02Jan97) id UAA03599; Wed, 12 Jan 2000 20:40:45 -0500 (EST) Date: Wed, 12 Jan 2000 20:40:45 -0500 (EST) From: Dana Craig Trantham X-Sender: dctranth@uni02du.unity.ncsu.edu To: "Dr. Kaltofen" Subject: Phone call compression Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-UIDL: e2ff22e5df1abcb24a5bcac511a2f100 Status: OR The old US compression (companding) is mu-255. Europe uses "A" law companders. The peaks are compressed and the low level signals are expanded. Compressed+expanded is companded. --------------------- Dana Trantham dctranth@eos.ncsu.edu --------------------- From dctranth@unity.ncsu.edu Thu Jan 13 23:45:21 2000 Received: from eos00mh.eos.ncsu.edu (eos00mh.eos.ncsu.edu [152.1.9.14]) by uni02mh.unity.ncsu.edu (8.8.7/8.8.7) with ESMTP id XAA21488 for ; Thu, 13 Jan 2000 23:45:21 -0500 (EST) Received: from stamp.math.ncsu.edu (stamp.math.ncsu.edu [152.1.30.228]) by eos00mh.eos.ncsu.edu (8.8.7/8.8.7) with ESMTP id XAA16296 for ; Thu, 13 Jan 2000 23:45:20 -0500 (EST) Received: from uni04du.unity.ncsu.edu (uni04du.unity.ncsu.edu [152.1.2.81]) by stamp.math.ncsu.edu (8.9.2/8.9.2) with ESMTP id XAA25919 for ; Thu, 13 Jan 2000 23:45:19 -0500 (EST) Received: (from dctranth@localhost) by uni04du.unity.ncsu.edu (8.8.4/EC02Jan97) id XAA10990; Thu, 13 Jan 2000 23:45:19 -0500 (EST) Date: Thu, 13 Jan 2000 23:45:18 -0500 (EST) From: Dana Craig Trantham X-Sender: dctranth@uni04du.unity.ncsu.edu To: "Dr. Kaltofen" Subject: mu law/A law links Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-UIDL: d6d2f70bcee0d9bccfc92be3a51d552d Status: OR The first 2 links will give you an idea of how these companding schemes work. The 3rd is a spec sheet for a Texas Instrument part. You can get more by searching on PCM, u-law, mu 255, A Law, etc. These come from the CCITT and Bell specifcations for telephony transmission. http://www.hut.fi/Misc/Electronics/docs/telecom/ulaw_alaw.html http://www.tcm.hut.fi/Opinnot/Tik-110.551/1997/seminar_paper.html http://www-d.connect.ti.com/dsp/tpcat/tpcodec.nsf/SoftwareForExternal/3B3BF2E87F3D01BC862567290051F39D --------------------- Dana Trantham dctranth@eos.ncsu.edu ---------------------