psearch.m

the implement of the encoder and the decoder of the CELP

function psearch(sube1)

global frames pdmin pdmax pcbsize pcode pgain TRUE FALSE
global shiftrange szsubf sub_cnt bpb intp pdlyindx pdelay frange prev del_intv

% For the first sub-frame, which is empty, just assume a pitch code
if sub_cnt==1                           
    pcode(sub_cnt)=1;
    prev=pcode(sub_cnt);
    pgain(sub_cnt)=0.0;
else

    % Integer pitch delay search

    % Move the intp+pdmin-1 behind of the pitch buffers ahead
    pdelay(1:intp+pdmin-1)=bpb(szsubf+1:intp+szsubf+pdmin-1);       
    
        if rem(sub_cnt-1,del_intv)~=0                    % Full pitch search only on first sub-frame for each frame.
            if (prev-shiftrange/2)<=1                    %   
                bkl=1;                                   %
                bkh=bkl+shiftrange-1;                    % Find search range for delta search use
            elseif (prev+shiftrange/2)>=pcbsize          %
                bkh=pcbsize;                             %
                bkl=bkh-shiftrange+1;                    %
            else                                         %
                bkl=prev-shiftrange/2;                   %
                bkh=prev+shiftrange/2-1;                 %
            end
            % Routine searching integer pitch delay and gain
            [pcodei,pgaini,pk1]=pdetect(pdelay,sube1,bkl,bkh,FALSE);   
        else
            bkl=1; bkh=pcbsize;                         % Full pitch search
            % Routine searching integer pitch delay and gain
            [pcodei,pgaini,pk1]=pdetect(pdelay,sube1,bkl,bkh,FALSE);    
            prev=0;
        end

    % Fractional pitch delay search
    
    bkl=max((pcodei-frange/2),bkl);                      % Define fractional pitch delay search (small range:6)
    bkh=min((pcodei+frange/2-1),bkh);
    
    % Routine searching fractional pitch delay and gain. Fractional and integer search use the same routine,
    % which differentiate itself with boolean flag TRUE/FALSE
    [pcodef,pgainf,pk2]=pdetect(pdelay,sube1,bkl,bkh,TRUE); %
    
    if pk2<=pk1                                          % Compare results from the integer and fractional searches
        pcode(sub_cnt)=pcodei-prev;                      % Select the better estimate of pitch delay and gain
        pgain(sub_cnt)=pgaini;
        prev=pcodei;
    else
        pcode(sub_cnt)=pcodef-prev;
        pgain(sub_cnt)=pgainf;
        prev=pcodef;
    end
    
end