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idct_2_simple.m
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idct_2_simple.m
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%=================================================================================
% Advanced Multimedia Applications
% Title : Simple 2D-IDCT (idct_2_simple.m)
% Description : Performs 2D-Inverse DCT using basic transform equations.
% Input : dct-coefficients(matrix)
% Output : original samples (matrix)
%=================================================================================
function dct2_result = idct_2_simple(coeffs)
N = length(coeffs); % we assume that height=width
% initialisation
XN = coeffs;
Xkl = zeros(N,N); % NxN matrix needed to store result
sum_i=0;
sum_j=0;
% first outer loop
for k=1:N
%second outer loop
for l=1:N
% first inner loop
for i = 1:N
% second inner loop
for j = 1:N
% calculating and adding the cj term
if(i==1)
ci = 1/sqrt(2);
else
ci = 1;
end;
if (j==1)
cj = 1/sqrt(2);
else
cj = 1;
end;
% inner main cosine calculation
inner = ci * cj * XN(i,j) * cos(((2*pi)*((i-1)/(2*N))*...
((k-1)+0.5))) * cos(((2*pi)*((j-1)/(2*N))*((l-1)+0.5)));
sum_j = sum_j + inner;
end
% get summarion for second inner loop
sum_i = sum_i + sum_j;
sum_j = 0;
end
% get result for first inner loop
Xkl(k,l) = (2/N) * sum_i;
sum_i = 0;
end
end
dct2_result = Xkl;