(To be removed) Inverse discrete cosine transform (IDCT)
The dsp.IDCT
System
object™ will be removed in a future release. Use idct
instead. For more information, see Compatibility Considerations.
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.
Starting in R2016b, instead of using the step
method to perform the operation defined by the System
object, you can call the object with arguments, as if it were a function. For
example, y = step(obj,x)
and y = obj(x)
perform equivalent operations.
idct = dsp.IDCT
returns a inverse discrete cosine transform
(IDCT) object, idct
. This object computes the IDCT of
a real or complex input signal using the Table lookup
method.
idct = dsp.IDCT('
returns an inverse discrete cosine transform (IDCT) object, PropertyName
',PropertyValue
,...)idct
, 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

step  Inverse discrete cosine transform (IDCT) of input 
Common to All System Objects  

release  Allow System object property value changes 
Note: This example runs only in
R2016b or later. If you are using an earlier release, replace each call to the
function with the equivalent step
syntax. For example,
myObject(x) becomes step(myObject,x).
Use DCT to analyze the energy content in a sequence:
x = (1:128).' + 50*cos((1:128).'*2*pi/40); dct = dsp.DCT; X = dct(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)]);
Number of DCT coefficients that represent 99.9%of the total energy in the sequence: 10
XXt = zeros(128,1); XXt(ind(1:ii)) = X(ind(1:ii)); idct = dsp.IDCT; xt = idct(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.