Inverse discrete cosine transform (IDCT)
IDCT object computes the inverse discrete
cosine transform (IDCT) of an input.
To compute the IDCT of an input:
Starting in R2016b, instead of using the
to perform the operation defined by the System
object™, you can
call the object with arguments, as if it were a function. For example,
= step(obj,x) and
y = obj(x) perform
idct = dsp.IDCT returns
a inverse discrete cosine transform (IDCT) object,
This object computes the IDCT of a real or complex input signal using
Table lookup method.
idct = dsp.IDCT(' returns
an inverse discrete cosine transform (IDCT) object,
with each property set to the specified value.
Method to compute sines and cosines
Specify how the IDCT object computes the trigonometric function
|step||Inverse discrete cosine transform (IDCT) of input|
|Common to All System Objects|
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(128-ii,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.
Usage notes and limitations:
See System Objects in MATLAB Code Generation (MATLAB Coder).