pitchvq.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.
%
% ******************************************************************
% PITCHVQ
%
% PORTED TO MATLAB FROM CELP 3.2a C RELEASE
% 7-8-94
%
% ******************************************************************
%
% DESCRIPTION
%
% Pitch VQ (n-taps, where n = 0, ..., 3) "self-excited" or
% "vq" or "adaptive codebook"
%
% DESIGN NOTES
%
% Adaptive code book (pitch) synthesis routine:
%
% 1) For lags < frame size:  gain-shape adaptive code book VQ
% 2) For lags => frame size this is equivalent to a pitch synthesis "filter"
%
%                          -[b(1)-1]        -b(1)        -[b(1)+1]
%   H(z) =  1 /  1 + b(2) z         + b(3) z     + b(4) z
%
%  NOTE: largest delay must not exceed the value IDIMB-IDIM
%
% REFERENCES
%
% 1. Singhal & Atal, Improving Performance of Multi-Pulse LPC Coders at
%    Low Bit Rates, ICASSP, 1984.
%
% 2. Rose & Barnwell.  The Self Excited Vocoder-An Alternate Approcch
%    to Toll Quality at 4800 bps, ICASSP, 1986, pp. 453-456.
%
% 3. Kleijn, Krasinski and Ketchum, Improved Speech Quality and
%    Efficient Vector Quantization in SELP, ICASSP, 1988.
%
% VARIABLES
%
% INPUTS
%   rar        -     Input data segment
%   buf        -     Data buffer
%   idim       -     Dimension of rar
%   idimb      -     Dimension of buf
%   b          -     Pitch predictor coefficients, beta1, beta2, beta3
%                    For a one-tap predictor, beta1 = beta3 = 0.00
%                    b(1) = Pitch delay (m)
%                    b(2-4) = Pitch predictor coefficients
%   type       -     Delay type used, long or short
%
% OUTPUTS
%   rar        -     Output data segment
%   buf        -     Data buffer
%
% INTERNALS
%   imin       -     Lower index for filter memory update segment
%   imax       -     Upper index for filter memory update segment
%   frac       -     Fractional delay component
%   k          -     Lower bound on filter update
%   m          -     Integer delay component
%   start      -     Lower bound on filter update
%   buf2       -     Delayed version of output signal
%
% CONSTANTS
%   MAXLP      -     Maximum pitch prediction frame size
%
% ******************************************************************

function [ rar, buf ] = pitchvq( rar, idim, buf, idimb, b, type )

% DECLARE CONSTANTS
global MAXLP

% INIT LOCALS
k = idimb - idim;
start = k + 1;
m = fix( b(1) );
frac = b(1) - m;
buf2 = zeros( MAXLP, 1 );

% UPDATE FILTER MEMORY
buf( 1:k ) = buf( (1+idim):(k+idim) );

% UPDATE FILTER MEMORY WITH SELECTED PITCH MEMORY FROM DELAY M
% MUST USE TWO BLOCK MOVES TO ACCOUNT FOR OVERLAP DURING DELAYS (M)
% LESS THAN IDIM (60 SAMPLES), OTHERWISE BEGINNING SEGMENT
% DOESN'T GET REPEATED.  SEE 'C' FOR LOOP FOR CLARIFICATION.
% IN ADDITION, MUST HANDLE TWO CASES FOR OVERLAP: CASE I, M<30
% MUST REPEAT STARTING PORTION MORE THAN ONCE.
% CASE II, M >= 30 REPEATS ONLY ONCE
if abs(frac) < 1.0e-4
    if ( idimb-m ) >= k+1
        if m < 30
            buf( (k+1):(k+m) ) = buf( (k-m+1):k );
            buf( (k+m+1):(k+m+m) ) = buf( (k+1):(k+m) );
            buf( (k+m+m+1):idimb ) = buf( (k+m+1):(idimb-m) );
        else
            buf( (k+1):(k+m) ) = buf( (k-m+1):k );
            buf( (k+m+1):idimb ) = buf( (k+1):(idimb-m) );
        end
    else
        buf( (k+1):idimb ) = buf( (k+1-m):(idimb-m) );
    end
end

% DO FRACTIONAL UPDATE IF FRACTIONAL PART ISN'T CLOSE ENOUGH TO 0
if abs(frac) > 1.0e-4
    if strcmp( type, 'long' ) == 1
        [ buf, buf2 ] = ldelay( buf, start, idim, frac, m );
    else
        [ buf, buf2 ] = delay( buf, start, idim, frac, m );
    end
    buf( (k+1):(k+idim) ) = buf2( 1:idim );
end

% RETURN RAR WITH SCALED MEMORY ADDED TO STOCHASTIC CONTRIBUTION
imin = k+1; imax = k+idim;
rar( 1:idim ) = rar( 1:idim ) + ( b(3) * buf( imin:imax ) );
buf( imin:imax ) = rar( 1:idim );