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均匀量化编码：

function[sqnr,a_quan,code]=upcm(a,n)

amax=max(abs(a));？？a、n怎样定义

a_quan=a/amax;

%抽样值归一化

b_quan=a_quan;

d=2/n;

q=d.*[0:n-1]-(n-1)/2*d;

%对归一化的输入信号序列进行量化

for i=1:n

index=find((q(i)-d/2<=a_quan)&(a_quan<=q(i)+d/2));

a_quan(index)=q(i).*ones(1,length(index));

b_quan(find(a_quan==q(i)))=(i-1).*ones(1,length(find(a_quan==q(i))))

end

a_quan=a_quan*amax;

nu=ceil(log2(n));

code=zeros(length(a),nu);

for i=1:length(a)

for j=nu:-1:0

if(fix(b_quan(i)/(2^j))==1)

code(i,nu-j)=1;

b_quan(i)=b_quan(i)-2^j;

end

end

end

sqnr=20*log10(norm(a)./norm(a-a_quan));

PCM编码：

function[out]=pcm_encode(x)

for i=1:n

if x(i)>0

out(i,1)=1;

else

out(i,1)=0

end

if abs(x(i))>0 & abs(x(i))<32

out(i,2)=0;out(i,3)=0;out(i,4)=0;step=2;st=0;??step跟st分别代表什么

elseif

abs(x(i))>=32 & abs(x(i))<64

out(i,2)=0;out(i,3)=0;out(i,4)=1;step=2;st=32;

elseif abs(x(i))>=64

& abs(x(i))<128

out(i,2)=0;out(i,3)=1;out(i,4)=0;step=4;st=64;

elseif

abs(x(i))>=128 & abs(x(i))<256

out(i,2)=0;out(i,3)=1;out(i,4)=1;step=8;st=128;

elseif

abs(x(i))>=256 & abs(x(i))<512

out(i,2)=1;out(i,3)=0;out(i,4)=0;step=16;st=256;

elseif

abs(x(i))>=512 & abs(x(i))<1024

out(i,2)=1;out(i,3)=0;out(i,4)=1;step=32;st=512;

elseif

abs(x(i))>=1024 & abs(x(i))<2048

out(i,2)=1;out(i,3)=1;out(i,4)=0;step=64;st=1024;

elseif

abs(x(i))>=2048 & abs(x(i))<4096

out(i,2)=1;out(i,3)=1;out(i,4)=1;step=128;st=2048;

else

out(i,2)=1,out(i,3)=1;out(i,4)=1;step=128;st=2048;

end

if(abs(x(i))>=4096)

out(i,2:8)=[1 1 1 1 1 1 1];？？？？

else

tmp=floor((abs(x(i))-st)/step);

t=dec2bin(tmp,4)-48; %函数dec2bin输出的是ASCII字符串，48对应0

out(i,5:8)=t(1:4);

end

end

out=reshape(out',1,8*n);

PCM译码：

function[out]=pcm_decode(in,v)

%decode the input pcm code

%in, input the pcm code 8bits sample

%v, quantized level

n=length(in);

in=reshape (in',8,n/8);

slot(1)=0;？？？

slot(2)=32;

slot(3)=64;

slot(4)=128;

slot(5)=256;

slot(6)=512;

slot(7)=1024;

slot(8)=2048;

step(1)=2;？？？

step(2)=2;

step(3)=4;

step(4)=8;

step(5)=16;

step(6)=32;

step(7)=64;

step(8)=128;

for i=1:n/8

ss=2*in(1,i)-1;

tmp=in(2,i)*4+in(3,i)*2+in(4,i)+1;

st=slot(tmp);

dt=(in(5,i)*8+in(6,i)*4+in(7,i)*2+in(8,i))*step(tmp)+0.5*step(tmp);

out(i)=ss*(st+dt)/4096*v;

end

主程序中：

figure(1)

for k=1:length(vm)

for m=1:2

x=vm(k)*sin(2*pi*4*t+2*pi*rand(1));

[sqnrM,zxx,zz]=upcm(x,M); %PCM均匀量化编码 ？？？？？直接不了解哇

srm(m)=sqnrM;

v=vm(k);

xx=x/v; %normalize

sxx=floor(xx*4096);

y=pcm_encode(sxx); %PCM编码

yy=pcm_decode(y,v); %PCM解码

nq(m)=sum((x-yy).*(x-yy))/length(x); %噪声平均功率

sq(m)=mean(yy.^2); %信号平均功率

snr(m)=(sq(m)/nq(m)); %信号量化信噪比

usnrq(k)=mean(srm);

snrq(k)=10*log10(mean(snr)); %量化信噪比

end

end