Programmer Guide/Command Reference/EVAL/dct: Difference between revisions
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;Usage:<code>dct(<var>x</var> {, <var>n</var> {, <var>dir</var>)</code> | ;Usage:<code>dct(<var>x</var> {, <var>n</var> {, <var>dir</var>)</code> | ||
:;<var>x</var>the data vector | :;<var>x</var>the data vector | ||
:;<var>n</var>:the number of dct coefficients to compute or to use (default=<code>nrow(''x'')); the meaning of this argument depends on the value of ''dir'' | :;<var>n</var>:the number of dct coefficients to compute or to use (default=<code>nrow(''x'')</code>); the meaning of this argument depends on the value of ''dir'' | ||
:;<var>dir</var>:the direction of the dct (default=0) | :;<var>dir</var>:the direction of the dct (default=0) | ||
:::{class="keinrahmen" | :::{class="keinrahmen" | ||
| Line 9: | Line 9: | ||
|- | |- | ||
|otherwise ||-> inverse (or backward) dct | |otherwise ||-> inverse (or backward) dct | ||
|} | |||
;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" | ||
Revision as of 13:10, 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-
lengthy nrow(y) description 0 data samples 0<n<=NXNX dct coefficients n forward dct; if n<NX only the first n coefficients are computed 1 dct coefficients 0<n<=NXNX data samples NX inverse dct; if n<NX only the first n coefficients of x are used (smoothing or liftering) 1 dct coefficients n>NXn 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)
