Package: dsp
Inverse discrete cosine transform (IDCT)
The IDCT
object computes the inverse discrete
cosine transform (IDCT) of an input.
To compute the IDCT of an input:
Define and set up your IDCT object. See Construction.
Call step
to compute the IDCT of an input according
to the properties of dsp.IDCT
. The behavior of step
is
specific to each object in the toolbox.
H = dsp.IDCT
returns
a inverse discrete cosine transform (IDCT) object, H
.
This object computes the IDCT of a real or complex input signal using
the Table lookup
method.
H = dsp.IDCT('
returns
an inverse discrete cosine transform (IDCT) object, PropertyName
',PropertyValue
,...)H
,
with each property set to the specified value.

Method to compute sines and cosines Specify how the IDCT object computes the trigonometric function
values as 
clone  Create inverse discrete cosine transform object with same property values 
getNumInputs  Number of expected inputs to step method 
getNumOutputs  Number of outputs of step method 
isLocked  Locked status for input attributes and nontunable properties 
release  Allow property value and input characteristics changes 
step  Inverse discrete cosine transform (IDCT) of input 
Use DCT to analyze the energy content in a sequence:
x = (1:128).' + 50*cos((1:128).'*2*pi/40); hdct = dsp.DCT; X = step(hdct, x); % Set the DCT coefficients which represent less % than 0.1% of the total energy to 0 and % reconstruct the sequence using IDCT. [XX, ind] = sort(abs(X),1,'descend'); ii = 1; while (norm([XX(1:ii);zeros(128ii,1)]) <= 0.999*norm(XX)) ii = ii+1; end disp(['Number of DCT coefficients that represent 99.9%',... 'of the total energy in the sequence: ',num2str(ii)]); XXt = zeros(128,1); XXt(ind(1:ii)) = X(ind(1:ii)); hidct = dsp.IDCT; xt = step(hidct, XXt); plot(1:128,[x xt]); legend('Original signal','Reconstructed signal',... 'location','best');
This object implements the algorithm, inputs, and outputs described on the IDCT block reference page. The object properties correspond to the block parameters.