Matlab: Discrete Cosine Transform (DCT) for speech processing

The DCT and inverse DCT may be used to convert a speech signal into the transform domain using real values and back to the speech waveform.

Example with Matlab:

%load speech

load mtlb

x = mtlb;

X = dct(x);

y = idct(X);

Results:

The values for x and y look the same, but MATLAB consider them as different.

>> isequal(x,y)

ans =

  logical

   0

For real-time processing, short-time DCT is required.

References:

Discrete Cosine Transform (Wikipedia)

dct (MathWorks)