TR-30.1/97-01-

Telecommunications Industry Association (TIA)

_________________________________________________________________
                           CONTRIBUTION
                                to
                  Technical Subcommittee TR-30.1
_________________________________________________________________

SOURCE:     Hayes Microcomputer Products, Inc.

CONTACT:    David C. Rife
            office  (770) 840-9200  ext 2048
            fax     (770) 447-0178

TITLE:      Digital Pad Mapping Program

PROJECT:    PN-3838

DATE:       February 28, 1997

DISTRIBUTION:   TR-30.1 Meeting Attendees


                             ABSTRACT

This contribution contains the BASIC program used to generate the
pad mapping tables of 3dbpadr1.txt.


                       Copyright Statement

The contributor grants a free, irrevocable license to the
Telecommunications Industry Association (TIA) to incorporate text
contained in this contribution and any modifications thereof in
the creation of a TIA standards publication; to copyright in
TIA's name any standards publication even though it may include
portions of this contribution; and at TIA's sole discretion to
permit others to reproduce in whole or in part the resulting TIA
standards publication.

                 Intellectual Property Statement

The individual preparing this contribution does not know of
patents, the use of which may be essential to a standard
resulting in whole or in part from this contribution.


'   Program to identify pad mapping for A-law and mu-law codecs.
'   by David Rife
'   12-31-96
'   01-02-97 Changed program to use command line loss value and
'            added marks to duplicate output levels.
'   01-03-97 Added duplicate level counter to P routine.
'   01-14-97 Made the mapping routine a subroutine.
'   02-28-97 Corrected bug in mu-law section.

'   This version uses the smaller of two output levels when both
'   have the same absolute error.

'   A-law codec output levels
    DATA 1, 3, 5, 7, 9, 11, 13, 15
    DATA 17, 19, 21, 23, 25, 27, 29, 31
    DATA 33, 35, 37, 39, 41, 43, 45, 47
    DATA 49, 51, 53, 55, 57, 59, 61, 63
    DATA 66, 70, 74, 78, 82, 86, 90, 94
    DATA 98, 102, 106, 110, 114, 118, 122, 126
    DATA 132, 140, 148, 156, 164, 172, 180, 188
    DATA 196, 204, 212, 220, 228, 236, 244, 252
    DATA 264, 280, 296, 312, 328, 344, 360, 376
    DATA 392, 408, 424, 440, 456, 472, 488, 504
    DATA 528, 560, 592, 624, 656, 688, 720, 752
    DATA 784, 816, 848, 880, 912, 944, 976, 1008
    DATA 1056, 1120, 1184, 1248, 1312, 1376, 1440, 1504
    DATA 1568, 1632, 1696, 1760, 1824, 1888, 1952, 2016
    DATA 2112, 2240, 2368, 2496, 2624, 2752, 2880, 3008
    DATA 3136, 3264, 3392, 3520, 3648, 3776, 3904, 4032

'   mu-law codec output levels
    DATA    0, 2, 4, 6, 8, 10, 12, 14
    DATA    16, 18, 20, 22, 24, 26, 28, 30
    DATA    33, 37, 41, 45, 49, 53, 57, 61
    DATA    65, 69, 73, 77, 81, 85, 89, 93
    DATA    99, 107, 115, 123, 131, 139, 147, 155
    DATA    163, 171, 179, 187, 195, 203, 211, 219
    DATA    231, 247, 263, 279, 295, 311, 327, 343
    DATA    359, 375, 391, 407, 423, 439, 455, 471
    DATA    495, 527, 559, 591, 623, 655, 687, 719
    DATA    751, 783, 815, 847, 879, 911, 943, 975
    DATA    1023, 1087, 1151, 1215, 1279, 1343, 1407, 1471
    DATA    1535, 1599, 1663, 1727, 1791, 1855, 1919, 1983
    DATA    2079, 2207, 2335, 2463, 2591, 2719, 2847, 2975
    DATA    3103, 3231, 3359, 3487, 3615, 3743, 3871, 3999
    DATA    4191, 4447, 4703, 4959, 5215, 5471, 5727, 5983
    DATA    6239, 6495, 6751, 7007, 7263, 7519, 7775, 8031

    DIM A(128), M(128), X(128), Y(128)

    FOR I = 1 TO 128    '   reading A-law table
        READ A(I)
    NEXT I

    FOR I = 1 TO 128    '   reading æ-law table
        READ M(I)
    NEXT I


    Q$ = COMMAND$   '   Note: remove this line if using QBASIC.

    IF Q$ = "" THEN INPUT "How many db of loss do you want";Q$
    IF Q$ = "" THEN END
    Q = VAL(Q$)
    R = 10 ^ (Q / 20)
    GOSUB A
    GOSUB M
    END

A:  '   A-law mapping
    LAW$ = "A"
    FOR I = 1 TO 128    'write the map to X(I)
        X(I) = A(I)
    NEXT I
    GOSUB S

    OPEN "PAD.OUT" FOR APPEND AS #1
    PRINT #1, ""
    PRINT #1, "Mapping of "; Q; "-db pad for A-law codec."
    GOSUB P
    CLOSE
    RETURN

M:  '   æ-law mapping
    LAW$ = "MU"
    FOR I = 1 TO 128    'write the map to X(I)
        X(I) = M(I)
    NEXT I
    GOSUB S

    OPEN "PAD.OUT" FOR APPEND AS #1
    PRINT #1, CHR$(12)
    PRINT #1, ""
    PRINT #1, "Mapping of "; Q; "-db pad for mu-law codec."
    GOSUB P
    CLOSE
    RETURN

S:  ' mapping routine
    FOR I = 1 TO 128
        Z = X(I) / R
        C = 10000
        FOR J = 1 TO 128
            IF ABS(X(J) - Z) < C THEN
                Y(I) = J
                C = ABS(X(J) - Z)
            END IF
        NEXT J
    NEXT I
    RETURN

P:  '  This bit does the rounding, counting of duplicates, and printing.
    DUPS = 0
    PRINT #1, ""
    PRINT #1, "index in      index out     level in      level out     error       duplicate"
    FOR I = 1 TO 128
        E0 = X(I) / R - X(Y(I))
        IF E0 < 0 THEN
            E = -INT(-100*E0 + .5)/100
            ELSE
                E = INT(100*E0 + .5)/100
            ENDIF
            PRINT X(I), X(Y(I)), E,
            IF LAW$ = "A" THEN PRINT #1, I, Y(I),
            IF LAW$ = "MU" THEN PRINT #1, I - 1, Y(I) - 1,
            PRINT #1, X(I), X(Y(I)), E,
        IF I = 1 THEN
            PRINT #1, ""
            PRINT
            ENDIF
        IF I > 1 THEN
            IF Y(I-1) = Y(I) THEN
                PRINT "*"
                PRINT #1, "*"
                DUPS = DUPS + 1
                ELSE
                    PRINT
                    PRINT #1,""
                ENDIF
            ENDIF
    NEXT I
    PRINT
    PRINT "Duplicates: ";DUPS
    PRINT #1, ""
    PRINT #1, "Duplicates: ";DUPS
    PRINT #1, ""
    RETURN

    END