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filters

DWT filter bank filters

Description

example

[Lo,Hi] = filters(fb) returns the lowpass (scaling) and highpass (wavelet) filters, Lo and Hi, respectively, for the discrete wavelet transform (DWT) filter bank fb.

Examples

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Obtain the lowpass and highpass filters for the order-4 symlet.

fb = dwtfilterbank('Wavelet','sym4');
[Lo,Hi] = filters(fb)
Lo = 8×2

   -0.0758    0.0322
   -0.0296   -0.0126
    0.4976   -0.0992
    0.8037    0.2979
    0.2979    0.8037
   -0.0992    0.4976
   -0.0126   -0.0296
    0.0322   -0.0758

Hi = 8×2

   -0.0322   -0.0758
   -0.0126    0.0296
    0.0992    0.4976
    0.2979   -0.8037
   -0.8037    0.2979
    0.4976    0.0992
    0.0296   -0.0126
   -0.0758   -0.0322

Confirm the filter bank is orthogonal.

isOrthogonal(fb)
ans = logical
   1

Input Arguments

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Discrete wavelet transform (DWT) filter bank, specified as a dwtfilterbank object.

Output Arguments

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Lowpass (scaling) filters for the DWT filter bank, returned as an L-by-2 matrix. L is an even positive integer. The first column of Lo is the analysis filter, and the second column is the synthesis filter.

For orthogonal wavelets, the lowpass synthesis and lowpass analysis filters are time-reversed versions of each other.

Highpass (wavelet) filters for the DWT filter bank, returned as an L-by-2 matrix. L is an even positive integer. The first column of Hi is the analysis filter, and the second column is the synthesis filter.

For orthogonal wavelets, the highpass synthesis and highpass analysis filters are time-reversed versions of each other.

Introduced in R2018a