Programmer Guide/Command Reference/EVAL/dct: Difference between revisions
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;Result: A vector ''y'' containing the result of the transformation. In the following table NX is equal to <code>nrow(''x'')</code> | ;Result: A vector ''y'' containing the result of the transformation. In the following table NX is equal to <code>nrow(''x'')</code> | ||
:{|class="einrahmen" | :{|class="einrahmen" | ||
!''dir'' !! ''n'' !! dct-<BR>length !! ''y'' !! nrow(''y'') !! description | !''dir'' !! ''x'' !! ''n'' !! dct-<BR>length !! ''y'' !! nrow(''y'') !! description | ||
|- | |- | ||
|'''0''' | |'''0''' | ||
|data samples | |||
|<code>0<''n''<=NX</code> | |<code>0<''n''<=NX</code> | ||
|NX | |NX | ||
| Line 21: | Line 22: | ||
|- | |- | ||
|'''1''' | |'''1''' | ||
|dct coefficients | |||
|<code>0<''n''<=NX</code> | |<code>0<''n''<=NX</code> | ||
|NX | |NX | ||
| Line 28: | Line 30: | ||
|- | |- | ||
|'''1''' | |'''1''' | ||
|dct coefficients | |||
|<code>''n''>NX</code> | |<code>''n''>NX</code> | ||
|''n'' | |''n'' | ||
Revision as of 13:09, 12 April 2011
Compute the forward or inverce discrete cosine transform (dct) of the input vector x. This function was implemented for the computation of the MFCC (mel-cepstrum coefficients)
- Usage
dct(x {, n {, dir)- xthe data vector
- n
- the number of dct coefficients to compute or to use (default=
nrow(x)); the meaning of this argument depends on the value of dir - dir
- the direction of the dct (default=0)
- {class="keinrahmen"
|dir=0 ||-> forward dct
|-
|otherwise ||-> inverse (or backward) dct
- Result
- A vector y containing the result of the transformation. In the following table NX is equal to
nrow(x)
dir
x
n
dct-
length
y
nrow(y)
description
0
data samples
0<n<=NX
NX
dct coefficients
n
forward dct; if n<NX only the first n coefficients are computed
1
dct coefficients
0<n<=NX
NX
data samples
NX
inverse dct; if n<NX only the first n coefficients of x are used (smoothing or liftering)
1
dct coefficients
n>NX
n
data samples
n
inverse dct; the vector x is expanded with zeros to length n and the inverse transform is applied to the expanded vector (smoothing or liftering)
