mtrxgen.m

实现fs1016w的CELP的低速率语音编解码功能的基于vc开发环境的原代码。

% MATLAB SIMULATION OF NSA FS-1016 CELP v3.2
% COPYRIGHT (C) 1995-99 ANDREAS SPANIAS AND TED PAINTER
%
% This Copyright applies only to this particular MATLAB implementation
% of the FS-1016 CELP coder.  The MATLAB software is intended only for educational
% purposes.  No other use is intended or authorized.  This is not a public
% domain program and distribution to individuals or networks is strictly
% prohibited.  Be aware that use of the standard in any form is goverened
% by rules of the US DoD.  Therefore patents and royalties may apply to
% authors, companies, or committees associated with this standard, FS-1016.  For
% questions regarding the MATLAB implementation please contact Andreas
% Spanias at [phone].  For questions on rules,
% royalties, or patents associated with the standard, please contact the DoD.
%
% ALL DERIVATIVE WORKS MUST INCLUDE THIS COPYRIGHT NOTICE.
%
% ******************************************************************
% MTRXGEN
%
% PORTED TO MATLAB FROM CELP 3.2a C RELEASE
% 6-7-94
%
% ******************************************************************
%
% DESCRIPTION
%
% Generate H matrix and syndrome table necessary for Hamming enocde
% and decode.
%
% DESIGN NOTES
%
% Part of a set of subroutines which perform a Generalized Hamming Code.
% Hamming codes are perfect codes and can only detect and
% correct one error.  We have added an overall parity checkbit,
% which allows detection of 2 errors.  When 2 errors
% are detected, (in decodeham) no correction attempt is
% made.  This would most likely result in more errors.  Instead, a flag
% is sent to the calling program notifying it of multiple errors so
% that smoothing may be attempted.  The Hamming codes presently
% supported by the routines are (63,57), (31,26), (15,11), and
% shortened variations thereof.  It could be made even more general
% by making minor modifications to the decimal to binary output vector
% code in the encodeham procedure.  This routine at present will
% calculate a maximum of 6 bits.
%
% CELP 3.2a Hamming routines include:
%   matrixgen - generates the hmatrix and sydrometable.
%   encodeham - generates the codeword and overall paritybit.
%   decodeham - recovers infobits, checks for errors, corrects 1
%               error, and sends out flag for smoothing.
%
% MATRIXGEN.M initializes all of the tables necessary to perform
% the Hamming code (G Matrix, Syndrome Table).
% Called once before calling encodeham and decodeham.
%
% REFERENCES
%   Lin and Costello:  Error Control Coding
%   Berlekamp:         Algebraic Coding Theory
%
% VARIABLES
%
% INPUTS
%   codelength1   -   Number of data bits
%   codelength2   -   Number of information bits
%
% OUTPUTS
%   hmatrix       -   Vector to encode and decode by
%   syndrometable -   Table containing error masks
%
% INTERNAL
%   i             -   Counter for table construction
%   temp1         -   Counter for table construction
%   itemplate     -   Identity template data
%   ptemplate     -   Parity template data
%
% ******************************************************************

function [ hmatrix, syndrometable ] = mtrxgen( codelength1, codelength2 )

% ALLOCATE RETURN VECTORS
hmatrix = zeros( codelength1, 1 );
syndrometable = zeros( codelength1, 1 );

% DEFINE DATA NECESSARY TO CONSTRUCT THE G MATRIX AND THE SYNDROME TABLE.
% IF A LARGER CODE IS DESIRED, THIS TABLE CAN BE EASILY ADDED TO.
% ALL OTHER ROUTINES, EXCEPT THE SYNDROME TABLE CONSTRUCTION,
% ARE GENERAL ENOUGH TO CALCULATE ANY SIZE HAMMING CODE.
itemplate = [ 1, 2, 4, 8, 16, 32 ]';
ptemplate = [ ...
              3,  5,  6,  7,  9,  10, 11, 12, 13, 14, 15, 17, 18, 19, 20, ...
              21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, ...
              37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, ...
              52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63              ...
            ]';

% CONSTRUCT THE PARITY PORTION OF THE HMATIX
hmatrix( 1:codelength2 ) = ptemplate( 1:codelength2 );

% CONSTRUCT THE IDENTITY PORTION OF THE MATRIX
hmatrix( 1+codelength2:codelength1 ) = itemplate( 1:codelength1-codelength2 );

% CONSTRUCT THE SYNDROME TABLE.  THIS ROUTINE EMPLOYS THE BERLEKAMP METHOD.
temp1 = 1;
for i = 1:codelength1
    if i == 1
        syndrometable(i) = codelength2 + 1;
    elseif i == 2
        syndrometable(i) = codelength2 + 2;
    elseif i == 4
        syndrometable(i) = codelength2 + 3;
    elseif i == 8
        syndrometable(i) = codelength2 + 4;
    elseif i == 16
        syndrometable(i) = codelength2 + 5;
    elseif i == 32
        syndrometable(i) = codelength2 + 6;
    else
        syndrometable(i) = temp1;
        temp1 = temp1 + 1;
    end
end