%%%% This code emulates(wat is it??) linear Pulse code Modulation %%%%
%%%%%%%%%% No Copyright (NoC) of Aditya Kumar %%%%%%%%%%%%%%%%%%%%
% Everyone is permitted to copy and distribute copies of this code %
clc
close all
clear all
choice=0;
%flag_iteration=1;
while(choice~=7) %Exit from menu
choice=menu('Pulse code modulation','Get PCM Parameters','Plot Input Signal','Sample','Quantize','Encode','Decode','Quit');
switch choice
case 1
close all
clear all
choice=1;
h1='o';
h2='o';
h3='o';
h4='o';
h5='o';
%=========Check no of times the loop runs=============
% flag_iteration=flag_iteration+1;
% if (flag_iteration>2)
% close all
%end
%==========================PCM parameters=========================
prompt={'Enter frequency of input sine wave','Enter amplitude for input sine wave','Enter n value for n-bit PCM','Enter no. of samples per second'};
dlg_title='PCM Parameters';
num_lines=1;
def={'2','5','8','20'};
options.Resize='on';
answer=inputdlg(prompt,dlg_title,num_lines,def,options);
% Conversion from string to number required
freq=str2double(answer{1});
amp=str2double(answer{2});
word_length=str2double(answer{3});
fs=str2double(answer{4});
%=============To generate input signal================================
t=0:.001:1;
w=2*pi*freq;
input_sig =amp*(sin(t*w));
%========Used later to create a window using 'figure' function========
scrsz = get(0,'ScreenSize'); %get dimension of screen
%=================================================================
%===================SAMPLING======================================
[~,n]=size(input_sig);
sample_size=round(n/(fs-1)); %To get n samples we divide data by n-1 so to get n points(samples) %Input signal divided into samples with each sample separated by sample_size
sampled_signal=zeros(1,fs);
index=1;
for i=1:sample_size-1:n
if(i>n-sample_size)
i=n;
end
sampled_signal(index)=input_sig(i);
index=index+1;
end
%===========Begin Quantization==============================
vmax=5; %get upper limit of quantization
vmin=-5; %get lower limit of quantization
lsb=(vmax-vmin)/((2^word_length)-1); %concept-if we divide a line segment in 2 parts we get three points
levels=vmin:lsb:vmax; %generate level vector
partition=(vmin-(.5*lsb)):lsb:(vmax+(.5*lsb)); %introduce +(-)1/2*LSB into levels
[~,index_levels]=size(levels);
%========generate quantized value out of sample data =========
quantiz_signal=zeros(1,index-1); %index-1??? see previous for loop, there index value exceeds size of sampled_signal in the last iteration
for i=1:index-1 %to increment the sampled_signal vector
for j=1:index_levels %to increment the 'partition' & 'levels' vectors
%============check if input is less than vmin============================================================
if (sampled_signal(i)<partition(1)) %Compare sample with upper and lower partition of a level
%if sample is between partitions, give that value of level to
%the quantize_signal array at the index equal to that of sample.
quantiz_signal(i)=vmin; %This will generate quantized array of same size of sample's array
bin_val=dec2bin(0,word_length); %for example- In 4-bit PCM quantize level 1 corresponds to 0x0 & level 16 is eqv to 0xf
%Following commands to arrange string bits columnwise and put it at appropriate index of data stream
val_rearrange=bin_val(:); %Make it i:1 matrix
rearrange_index=((i-1)*word_length)+1; %Example- for 4 bit insert at 1st,5th,9th,13th..index
data_stream(rearrange_index:(rearrange_index+word_length-1),1)=val_rearrange;
end
%==============check if input is greater than vmax===========================================================
if (sampled_signal(i)>partition(end))
quantiz_signal(i)=vmax;
bin_val=dec2bin((2^word_length)-1,word_length); %for example- In 4-bit PCM quantize level 1 corresponds to 0x0 & level 16 is eqv to 0xf
%Following commands to arrange string bits columnwise and put it at appropriate index of data stream
val_rearrange=bin_val(:); %Make it i:1 matrix
rearrange_index=((i-1)*word_length)+1; %Example- for 4 bit insert at 1st,5th,9th,13th..index
data_stream(rearrange_index:(rearrange_index+word_length-1),1)=val_rearrange;
end
%=========================================================================
if (sampled_signal(i)>=partition(j))
if (sampled_signal(i)<partition(j+1))
quantiz_signal(i)=levels(j);
%=====Simultaneously generating binary stream for each quantized value====
bin_val=dec2bin(j-1,word_length); %for example- In 4-bit PCM quantize level 1 corresponds to 0x0 & level 16 is eqv to 0xf
%Following commands to arrange string bits columnwise and put it at appropriate index of data stream
val_rearrange=bin_val(:); %Make it i:1 matrix
rearrange_index=((i-1)*word_length)+1; %Example- for 4 bit insert at 1st,5th,9th,13th..index
data_stream(rearrange_index:(rearrange_index+word_length-1),1)=val_rearrange;
end
end
end
end
%==========================================================================
[size_data,~]=size(data_stream);
%=================create Encoded data stream array ========================
%==============Encoded according to Natural Binary Coding==================
dec_val=zeros(size_data,1);
for i=1:size_data
dec_val(i,1)=str2double(data_stream(i,1)); %cant plot string array. so convert to numbers
end
%===========================Decoding=======================================
k=1;
for i=1:length(data_stream)/word_length %Arrange data stream into word_length sized binary strings for conversion
for j=1:1:word_length
bin_rearrange(i,j)=data_stream(k); %Ignoring this Warning!!!!
k=k+1;
end
end
bin_rearrange
bin_dec=bin2dec(bin_rearrange);
decoded_val=zeros(length(bin_dec),1);
for i=1:length(bin_dec) %bin_dec contain dec equivalents ranging from 0 to max for the word
decoded_val(i)=levels(bin_dec(i)+1); %therefore dec equivalent 0 corresponds to level 1.
%thus get quantized values from level(dec.equiv+1) and store in an array
end
%==============Various Plot data==========================================
case 2
h1=figure('Name','Input Signal','NumberTitle','off','Position',[122 scrsz(4)/3 scrsz(3)/2.2 scrsz(4)/2.2]); %Position figure accordingly
plot(t,input_sig);
axis([-inf inf -1.2*amp 1.2*amp]);
case 3
h2=figure('Name','Sampled Signal','NumberTitle','off','Position',[scrsz(3)/1.8 scrsz(4)/3 scrsz(3)/2.2 scrsz(4)/2.2]);
stem(sampled_signal);
case 4
if(~ischar(h1))
close(h1);
end
h3=figure('Name','Quantized Signal','NumberTitle','off','Position',[122 1 scrsz(3)/2.2 scrsz(4)]);
stairs(quantiz_signal)
ylim([vmin vmax])
%only to customize plot
set(gca,'YTick',vmin:lsb:vmax)
case 5
h4=figure('Name','Pulse Code Modulated Stream','NumberTitle','off','Position',[1 scrsz(4)/3 scrsz(3) scrsz(4)/2.5]);
stairs(dec_val');
axis([1 100 -3 4]);
set(gca,'YTick',-3:1:4);
set(gca,'YTicklabel',{' ',' ',' ','0','1',' ',' ',' '});
case 6
if(~ischar(h2))
close(h2);
end
if(~ischar(h4))
close(h4);
end
h5=figure('Name','Decoded Signal','NumberTitle','off','Position',[scrsz(3)/1.8 scrsz(4)/3 scrsz(3)/2.2 scrsz(4)/2.2]);
plot(decoded_val);
grid on;
%ylim([vmin vmax])
end
end
close all
