72 lines
2.6 KiB
Matlab
72 lines
2.6 KiB
Matlab
clc
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%================================================
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%已知抽样值以△为单位
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%================================================
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x = 2047 %抽样值/量化单位△
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pcmcode = pcmEnCode(x) %调用pcmCode()函数实现PCM编码
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amp = pcmDeCode(pcmcode) %调用pcmDecode()函数实现PCM译码
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amp = pcmDecode(pcmcode)
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%qerror = x-amp %求量化误差
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%================================================
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%已知抽样值为实际电压值，则需先转换为以△为单位
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%================================================
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% M = 5; %设置量化范围 -5~+5
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% delta = M/2^11; %求量化单位△
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% y = +2.5 %设置抽样值/V
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% y0 = round(y/delta) %将抽样值转换为以△为单位
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% pcmcode = pcmCode(y0) %PCM编码
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% amp=pcmDecode(pcmcode); %PCM译码
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% amp = amp*delta %转换为实际电压值
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% qerror=y-amp %求量化误差
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function pcmcode = pcmEnCode(s)
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start_t=[0,2.^(4:11)];
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width_t=[1,1,2,4,8,16,32,64];
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pcm=0;
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if s>0
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pcm=pcm+bitshift(1,7);
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else
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s=abs(s)
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end
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for i = 0:7
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if s < start_t(i+2)
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pcm=pcm+bitshift(i,4);
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pcm=pcm+floor((s-start_t(i+1))/width_t(i+1));
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break
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end
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end
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pcmcode=dec2bin(pcm,8);
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end
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function amp = pcmDeCode(pcmcode)
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start_t=[0,2.^(4:11)];
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width_t=[1,1,2,4,8,16,32,64];
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code=bin2dec(pcmcode);
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isNeg=0;
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if code < 128
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isNeg=1;
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k=bitshift(bitand(code,0b01111111),-4);
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amp=start_t(k+1) ...
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+ double(mod(bitand(code,0b01111111),16)) ...
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* width_t(k+1);
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if isNeg=1 amp=-amp;end
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end
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%PCM译码函数
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function amp = pcmDecode(pcmcode)
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code_table=[0,2.^(4:11)]; %段落起始电平表
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delta=[1,1,2,4,8,16,32,64]; %段内量化间隔表
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codeDec=bin2dec(pcmcode); %二进制编码字符串转换为十进制数值
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ucode=bitand(codeDec,0b01111111); %屏蔽极性位
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k=bitshift(ucode,-4); %右移4位，提取段落码
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x0=code_table(k+1); %查表求段落起始电平
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m=bitand(ucode,0b00001111); %提取段内码
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x1=double(m)*delta(k+1); %求段内量化电平
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dV=x0+x1+delta(k+1)/2; %译码输出电平
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if codeDec<=128 %处理极性
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amp=-dV;
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else
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amp=dV;
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end
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end
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