pdetect.m

the implement of the encoder and the decoder of the CELP

function [pcode, pgain, pk]=pdetect(pdelay,sube1,bkl,bkh,fracflg)

global h len cbsize szsubf pcbsize fstfrm intp pdmin pdmax pdlyindx

if fracflg==1
    % Fractional delay search
    start=intp+pdmin;                                        % Start point for computing fractional delay vector
    c=bkh-bkl; i=0;
    while (i<=c)
        m=fix(pdlyindx(bkl+i));
        frac=pdlyindx(bkl+i)-m;
        if frac>10e-6
            [pdelay,fracdly(i+1,:)]=interpolate(pdelay,start,szsubf,frac,m);      % All interpolate.m all equal either 1 or 0 (avoid FirstCom flag getting error)
            
            for j=0:szsubf-1                                                        %Convolution of the fractional delays with weighting filter
                endpt=min(j,len-1);
                y(i+1,j+1)=sum(h(1:endpt+1).*fracdly(i+1,1+j:-1:1+j-endpt));
            end
            yy(i+1,:)=y(i+1,:);
        
            cor(i+1)=sum(yy(i+1,:).*sube1);
            eng(i+1)=sum(yy(i+1,:).*yy(i+1,:));
            gain(i+1)=cor(i+1)/eng(i+1);
            peak(i+1)=gain(i+1)*cor(i+1);
        else
            peak(i+1)=-10e5;
            gain(i+1)=0.0;
        end
        i=i+1;
    end

    [pk,pcode]=max(peak);           % Find the best estimate of fractional delay and gain
    pgain=gain(pcode);
    pcode=bkl+pcode-1;
    
else
    
    % Integer delay search
    strptr=pdmax+1-fix(pdlyindx(bkh));             % Find computation start point in pitch delay buffer
    endptr=pdmax+1-ceil(pdlyindx(bkl));            % Find computation end point in pitch delay buffer
    
    for i=0:szsubf-1
        endpt=min(i,len-1);                                                         %compute conv before interpolation
        y(endptr,i+1)=sum(h(1:endpt+1).*pdelay(endptr+i:-1:i-endpt+endptr));
    end
    
    for i=endptr-1:-1:strptr
        y(i,1)=h(1)*pdelay(i);                                       % End point correction
        y(i,2:len)=y(i+1,1:len-1)+h(2:len)*pdelay(i);
        y(i,len+1:szsubf)=y(i+1,len:szsubf-1);
    end

    for i=strptr:endptr
        yy(i,:)=y(i,:);
        m=intp+pdmin-i;                                          % M=pitch delay
        if m<szsubf
            yy(i,m+1:szsubf)=y(i,m+1:szsubf)+y(i,1:szsubf-m);        % For m<size of sub-frame, 
            if m<fix(szsubf/2)                                       % do 2nd and 3rd convolution addition
                ilow=(2*m)+1;
                ihigh=szsubf;
                yy(i,ilow:ihigh)=yy(i,ilow:ihigh)+y(i,1:szsubf-(2*m));
            end
        end
    end
    % Compute Correlation and Eng. and get the best pitch coefficient
    for i=strptr:endptr                                              
        cor(i)=sum(yy(i,:).*sube1);
        eng(i)=sum(yy(i,:).*yy(i,:));
        gain(i)=cor(i)/eng(i);
        peak(i)=gain(i)*cor(i);
    end
    [pk,pcode]=max(peak(strptr:endptr));            % Find the best estimate of integer pitch delay and gain
    pcode=pcode+strptr-1;
    pgain=gain(pcode);
    pcode=find(pdlyindx==(pdmax+1-pcode));          % Translate the position into corresponding index in pitch delay table
end