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idct_2_8x8.m
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idct_2_8x8.m
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%=================================================================================
% Advanced Multimedia Applications
% Title : 2D-IDCT (8x8 block), using 1D-IDCT (idct_2_8x8.m)
% Description : Performs 2D-Inverse DCT using basic transform equations.
% Input : mat2d - input matrix is a bxb matrix
% b - block size
% idct_type = 1('fast idct'), 0('simple idct')
% Output : original samples (matrix)
%=================================================================================
function idct_2_result = idct_2_8x8(mat2d,b, idct_type)
% check if the supplied block size matches the matrix size
if(b ~= length(mat2d))
error('Input Matrix size does not match block size');
end
% check dct type - fast/simple
if(idct_type == 1 || idct_type == 0)
if(idct_type == 1)
if(b ~= 8)
error('Fast IDCT can only be supported for 8x8 blocks');
end
end
else
error('Unknown IDCT Type, select 1(fast), 0(slow)');
end
% preallocate for speed
idct_block = zeros(b,b);
idct_block2 = zeros(b,b);
% first do cols
for i = 1:b
if(idct_type == 1)
idct_block(:,i) = fidct_1(double(mat2d(:,i))); % cols (fast)
else
idct_block(:,i) = idct_1(double(mat2d(:,i))); % cols (simple)
end
end
idct_block_rows = idct_block;
% then do columns on the transform of the rows
for j = 1:b
if(idct_type == 1)
idct_block2(j,:) = fidct_1(double(idct_block_rows(j,:))); % rows (fast)
else
idct_block2(j,:) = idct_1(double(idct_block_rows(j,:))); % rows (simple)
end
end
% invert the output
idct_2_result = idct_block2';