PCM仿真均匀量化、非均匀量化及A律13折线编码

clc; clear all; close all; A=1;%原信号幅度 L1=[8,12];%编码位数 tc=1/200000; t=0:tc:1; x0=sin(2*pi*t); r=0:5:50;%信号的衰减分贝 sqnr=zeros(1,length(r));%声明一个矩阵sqnr %% %8、12位均匀量化 for j=1:2 L=L1(j); for i=1:length(r) A1=1/(10^(r(i)/20)); x=A1*x0; %2000Hz抽样 f=1/2000; t1=0:f:1; y1=downsample(x,f/tc);%每隔100个点对x1采样，即2000Hz抽样 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %2^L=256级均匀量化 M=2^L; [index,y2]=quantiz(y1,-(M-1)/M:2/M:(M-1)/M, -1:2/M:1); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %量化信噪比的计算 sqnr(i)=10*log10(mean(y1.^2)/mean((y1-y2).^2));%求量化信噪比,由于这里norm是求平方和后再开平方根，因此前面的系数为20 end if j==1 plot(r,sqnr,'*-'); hold on else plot(r,sqnr,'r o-'); title('量化信噪比随信号衰减变化的曲线'); hold on; end end %% %8位非均匀量化 L=L1(1);%重置量化位数 A1=87.6;%A律参数 for i=1:length(r) x=x0/(10^(r(i)/20));%信号衰减 xmax=max(abs(x)); x1=zeros(1,200001); for j=1:200001 if abs(x(j))<=1/A1 x1(j)=A1*x(j)/(1+log(A1)); else x1(j)=sign(x(j))*(1+log(A1*abs(x(j))))/(1+log(A1)); end %A律压缩 end %2000Hz抽样 f=1/2000; t1=0:f:1; y1=downsample(x1,f/tc);%每隔100个点对x1采样，即2000Hz抽样 yy=downsample(x,f/tc); M=2^L; [index,y2]=quantiz(y1,-(M-1)/M:2/M:(M-1)/M, -1:2/M:1); x2=zeros(1,2001); for k=1:2001 %A律扩展 if abs(y2(k))<=1/(1+log(A1)) x2(k)=y2(k)*(1+log(A1))/A1; else x2(k)=sign(y2(k))/A1*exp(abs(y2(k))*(1+log(A1))-1); end end %量化信噪比的计算 h=norm(yy-x2); h1=norm(yy); sqnr(i)=10*log10(mean(yy.^2)/mean((yy-x2).^2));%求量化信噪比,由于这里norm是求平方和后再开平方根，因此前面的系数为20 end %figure(10); plot(r,sqnr,'g +-'); grid on; title('量化信噪比随信号衰减变化的曲线'); xlabel('信号衰减（dB）'); ylabel('量化信噪比'); axis([0 50 0 80]); legend('8位均匀量化','12位均匀量化','8位非均匀量化');