intsynth.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 602) 965-1837.  For questions on rules,
% royalties, or patents associated with the standard, please contact the DoD.
%
% ALL DERIVATIVE WORKS MUST INCLUDE THIS COPYRIGHT NOTICE.
%
% ******************************************************************
% INTSYNTH
%
% PORTED TO MATLAB FROM CELP 3.2a C RELEASE
% 8-3-94
%
% ******************************************************************
%
% DESCRIPTION
%
% Linearly interpolate between transmitted LSPs to generate 4
% intermediate sets of LSP frequencies for subframe synthesis.
%
% DESIGN NOTES
%
% Linearly interpolates lsp's for synthesis in nn (=4) subframes.
% This version is only for use with absolute scalar LSP coding.
% The interpolated LSPs are identical to the interpolated set in the
% transmitter provided there are no transmission errors.  If the
% LSP's are nonmonotonic, then LSP errors have occured and an
% attempt is made to "fix" them by repeating previous LSP values.
% If this correction fails (the vector is still nonmonotonic),
% then the entire previous LSP vector is repeated.  (This version
% ignores twoerror and syndavg.)
%
% VARIABLES
%
% INPUTS
%   nn         -     Number of subframes per frame
%   lspnew     -     New frequency array (LSPs)
%   no         -     Number of LSPs
%   twoerror   -     Flag for occurrence of two errors in hamming
%                    protected bits
%   syndavg    -     Bit error estimation parameter
%
% OUTPUTS
%   lsp        -     Interpolated frequency matrix
%
% INTERNALS
%   i          -     Loop counter
%
% GLOBALS
%   FrameCnt   -     Current frame number
%   wIS        -     Interpolation weights
%   lspoldIS   -     Previous frame LSPs
%
% ******************************************************************

function lsp = intsynth( lspnew, nn, no, twoerror, syndavg )

% DECLARE GLOBAL/STATIC VARIABLES
global wIS lspoldIS FrameCnt

% CHECK LSPs; TRY TO FIX NONMONOTONIC LSPs BY REPEATING PAIR
if any( lspnew(2:no) <= lspnew(1:no-1) )
	for i = 2:no
	    if lspnew(i) <= lspnew(i-1)
            fprintf( 'intsynth: Try to fix nonmonotonic LSPs\n' );
            lspnew(i) = lspoldIS(i);
            lspnew(i-1) = lspoldIS(i-1);
	    end
	end
end

% RECHECK FIXED LSPs
if any( lspnew(2:no) <= lspnew(1:no-1) )

    % REPEAT ENTIRE LSP VECTOR IF NONMONOTONICITY HAS PERSISTED
    fprintf( 'intsynth: Repeat entire LSP vector @ frame %d\n', FrameCnt );
    lspnew = lspoldIS;
end

% INTERPOLATE LSPs AND TEST FOR MONOTONICITY
for i = 1:nn
    lsp( i, 1:no ) = ( ( wIS(1,i) * lspoldIS( 1:no ) ) + ...
                       ( wIS(2,i) * lspnew( 1:no ) ) )';

    % CHECK FOR MONOTONICALLY INCREASING LSPs
    if any( lsp(i,2:no) <= lsp(i,1:no-1) )
		fprintf( 'intsynth: Nonmonotonic LSPs @ frame %d\n', FrameCnt );
	end
end

% UPDATE LSP HISTORY
lspoldIS = lspnew;