Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!amdahl!pacbell!varian!kinetics!zehntel!bales!nat
From: nat@bales.UUCP (Nathaniel Stitt)
Newsgroups: sci.electronics
Subject: Re: CODEC - How to get one?
Summary: mu-law look up table.
Message-ID: <197@bales.UUCP>
Date: 18 Oct 88 23:12:59 GMT
References: <375@limbic.UUCP>
Reply-To: nat@bales.UUCP (Nathaniel Stitt)
Organization: Bales Scientific Inc., Walnut Creek, CA
Lines: 288

In article <375@limbic.UUCP> gil@limbic.UUCP (Gil Kloepfer Jr.) writes:
>Recently, I have been playing around with sound digitization, and was able
>to get a peek at a commerical unit.  It had a chip in it that was referred
>to as a CODEC.  This appears to be a A/D & D/A converter with an audio
>compression that they refer to as mu and A law.
>
>Can anyone provide input on what the mu and A law compression schemes are,

Here is a look up table I created a while back for going from 8-bit mu-law
encoded samples to 13-bit signed linear samples.  I generated this table
from a description of mu-law from a book I got at Radio Shack, so no
guarantees.  You should use the 8-bit mu-law value as an unsigned 8-bit
index into the table.


Here is the table:

short u2norm[256] =
{
	-4016,
	-3888,
	-3760,
	-3632,
	-3504,
	-3376,
	-3248,
	-3120,
	-2992,
	-2864,
	-2736,
	-2608,
	-2480,
	-2352,
	-2224,
	-2096,
	-2000,
	-1936,
	-1872,
	-1808,
	-1744,
	-1680,
	-1616,
	-1552,
	-1488,
	-1424,
	-1360,
	-1296,
	-1232,
	-1168,
	-1104,
	-1040,
	-992,
	-960,
	-928,
	-896,
	-864,
	-832,
	-800,
	-768,
	-736,
	-704,
	-672,
	-640,
	-608,
	-576,
	-544,
	-512,
	-488,
	-472,
	-456,
	-440,
	-424,
	-408,
	-392,
	-376,
	-360,
	-344,
	-328,
	-312,
	-296,
	-280,
	-264,
	-248,
	-236,
	-228,
	-220,
	-212,
	-204,
	-196,
	-188,
	-180,
	-172,
	-164,
	-156,
	-148,
	-140,
	-132,
	-124,
	-116,
	-110,
	-106,
	-102,
	-98,
	-94,
	-90,
	-86,
	-82,
	-78,
	-74,
	-70,
	-66,
	-62,
	-58,
	-54,
	-50,
	-47,
	-45,
	-43,
	-41,
	-39,
	-37,
	-35,
	-33,
	-31,
	-29,
	-27,
	-25,
	-23,
	-21,
	-19,
	-17,
	-15,
	-14,
	-13,
	-12,
	-11,
	-10,
	-9,
	-8,
	-7,
	-6,
	-5,
	-4,
	-3,
	-2,
	-1,
	0,
	4016,
	3888,
	3760,
	3632,
	3504,
	3376,
	3248,
	3120,
	2992,
	2864,
	2736,
	2608,
	2480,
	2352,
	2224,
	2096,
	2000,
	1936,
	1872,
	1808,
	1744,
	1680,
	1616,
	1552,
	1488,
	1424,
	1360,
	1296,
	1232,
	1168,
	1104,
	1040,
	992,
	960,
	928,
	896,
	864,
	832,
	800,
	768,
	736,
	704,
	672,
	640,
	608,
	576,
	544,
	512,
	488,
	472,
	456,
	440,
	424,
	408,
	392,
	376,
	360,
	344,
	328,
	312,
	296,
	280,
	264,
	248,
	236,
	228,
	220,
	212,
	204,
	196,
	188,
	180,
	172,
	164,
	156,
	148,
	140,
	132,
	124,
	116,
	110,
	106,
	102,
	98,
	94,
	90,
	86,
	82,
	78,
	74,
	70,
	66,
	62,
	58,
	54,
	50,
	47,
	45,
	43,
	41,
	39,
	37,
	35,
	33,
	31,
	29,
	27,
	25,
	23,
	21,
	19,
	17,
	15,
	14,
	13,
	12,
	11,
	10,
	9,
	8,
	7,
	6,
	5,
	4,
	3,
	2,
	1,
	0
};

>
>Gil Kloepfer, Jr.          U-Net: {decuac,boulder,talcott,sbcs}!icus!limbic!gil
>ICUS Software Systems      Voice: (516) 968-6860 [H]   (516) 746-2350 x219 [W]
>P.O. Box 1                 Internet:  gil@icus.islp.ny.us
>Islip Terrace, NY  11752   "Life's a ...  well, you know..."


-- 
Nathaniel Stitt           | This life is a test.  It is only a test.  Had
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