proclpc.txt

简单lpc音码器与声激励lpc音码器比较

function[aCoeff,resid,pitch,G,parcor,stream]=proclpc(data,sr,L,fr,fs,preemp)
if(nargin<3),L=13;end
if(nargin<4),fr=20;end
if(nargin<5),fs=30;end
if(nargin<6),preemp=.9378;end
[row col]=size(data);
if col==1 data=data';end
nframe=0;
msfr=round(sr/1000*fr);
msfs=round(sr/1000*fs);
duration=length(data);
speech=filter([1-preemp],1,data)';
msoverlap=msfs-msfr;
ramp=[0:1/(msoverlap-1):1]';
for frameIndex=1:msfr:duration-msfs+1%frame rate=20ms
frameData=speech(frameIndex:(frameIndex+msfs-1));
nframe=nframe+1;
autoCor=xcorr(frameData);
autoCorVec=autoCor(msfs+[0:L]);
err(1)=autoCorVec(1);
k(1)=0;
A=[];
for index=1:L
    numerator=[1 A.']*autoCorVec(index+1:-1:2);
    denominator=-1*err(index);
    k(index)=numerator/denominator;
    A=[A+k(index)*flipud(A);k(index)];
    err(index+1)=(1-k(index)^2)*err(index);
end
aCoeff(:,nframe)=[1;A];
Parcor(:,nframe)=k';
if 0
    gain=0;
    cft=0:(1/255):1;
for index=1:L
    gain=gain+aCoeff(index,nframe)*exp(-i*2*pi*cft).^index;
end
gain=abs(1./gain);
spec(:,nframe)=20*log10(gain(1:128))';
plot(20*log10(gain));
title(nframe);
drawnow;
end
if 0
    impulseResponse=filter(1,aCoeff(:,nframe),[1 zeros(1,255)]);
    freqResp=20*log10(abs(fft(impulseResponse)));
    plot(filter);
end
errSig=filter([1 A'],1,frameData);
G(nframe)=sqrt(err(L+1));
autoCorErr=xcorr(errSig);
[B,I]=sort(autoCorErr);
num=length(I);
if B(num-1)>.01*B(num)
pitch(nframe)=abs(I(num)-I(num-1));
%else
    pitch(nframe)=0;
end
resid(:,nframe)=errSig/G(nframe);
if(frameIndex==1)
    stream=resid(1:msfr,nframe);
else
    stream=[stream;
        overlap+resid(1:msoverlap,nframe).*ramp;
        resid(msoverlap+1:msfr,nframe)];
end
if(frameIndex+msfr+msfs-1>duration)
    stream=[stream;resid(msfr+1:msfs,nframe)];
else
    overlap=resid(msfr+1:msfs,nframe).*flipud(ramp);
end
end
stream=filter(1,[1-preemp],stream)';