🚀 go-pugleaf

In the referenced message, cfreese@super.UUCP (Craig F. Reese) wrote:
}Below are two routines I wrote for converting between ulaw and linear. 
}I use them with the SparcStation and they seem to work fine.

Thanks, those will be very useful.

Since I haven't seen anyone else post it, appended is the obvious
table-lookup version of Craig's ulaw to linear converter.  I did
some timings on a SPARCstation.  In nanoseconds:

    counting subroutine call    not counting subroutine call
        old         new               old         new 

       1217         557               913         253

Also, the table in interesting in its own right, to get a feel for
just what ulaw does.  Corrections welcome, otherwise enjoy.
---
Jef

    Jef Poskanzer  pokey@well.sf.ca.us  {ucbvax, apple, hplabs}!well!pokey
               Specifications subject to change without notice.

/*
** This routine converts from ulaw to 16 bit linear, but faster.
**
** Jef Poskanzer
** 23 October 1989
**
** Input: 8 bit ulaw sample
** Output: signed 16 bit linear sample
*/

int
ulaw2linear(ulawbyte)
unsigned char ulawbyte;
{
    static int ulaw_table[] = {
	-32124, -31100, -30076, -29052, -28028, -27004, -25980, -24956, 
	-23932, -22908, -21884, -20860, -19836, -18812, -17788, -16764, 
	-15996, -15484, -14972, -14460, -13948, -13436, -12924, -12412, 
	-11900, -11388, -10876, -10364,  -9852,  -9340,  -8828,  -8316, 
	 -7932,  -7676,  -7420,  -7164,  -6908,  -6652,  -6396,  -6140, 
	 -5884,  -5628,  -5372,  -5116,  -4860,  -4604,  -4348,  -4092, 
	 -3900,  -3772,  -3644,  -3516,  -3388,  -3260,  -3132,  -3004, 
	 -2876,  -2748,  -2620,  -2492,  -2364,  -2236,  -2108,  -1980, 
	 -1884,  -1820,  -1756,  -1692,  -1628,  -1564,  -1500,  -1436, 
	 -1372,  -1308,  -1244,  -1180,  -1116,  -1052,   -988,   -924, 
	  -876,   -844,   -812,   -780,   -748,   -716,   -684,   -652, 
	  -620,   -588,   -556,   -524,   -492,   -460,   -428,   -396, 
	  -372,   -356,   -340,   -324,   -308,   -292,   -276,   -260, 
	  -244,   -228,   -212,   -196,   -180,   -164,   -148,   -132, 
	  -120,   -112,   -104,    -96,    -88,    -80,    -72,    -64, 
	   -56,    -48,    -40,    -32,    -24,    -16,     -8,      0, 
	 32124,  31100,  30076,  29052,  28028,  27004,  25980,  24956, 
	 23932,  22908,  21884,  20860,  19836,  18812,  17788,  16764, 
	 15996,  15484,  14972,  14460,  13948,  13436,  12924,  12412, 
	 11900,  11388,  10876,  10364,   9852,   9340,   8828,   8316, 
	  7932,   7676,   7420,   7164,   6908,   6652,   6396,   6140, 
	  5884,   5628,   5372,   5116,   4860,   4604,   4348,   4092, 
	  3900,   3772,   3644,   3516,   3388,   3260,   3132,   3004, 
	  2876,   2748,   2620,   2492,   2364,   2236,   2108,   1980, 
	  1884,   1820,   1756,   1692,   1628,   1564,   1500,   1436, 
	  1372,   1308,   1244,   1180,   1116,   1052,    988,    924, 
	   876,    844,    812,    780,    748,    716,    684,    652, 
	   620,    588,    556,    524,    492,    460,    428,    396, 
	   372,    356,    340,    324,    308,    292,    276,    260, 
	   244,    228,    212,    196,    180,    164,    148,    132, 
	   120,    112,    104,     96,     88,     80,     72,     64, 
	    56,     48,     40,     32,     24,     16,      8,      0 };

    return ulaw_table[ulawbyte];
    }