Wavelet packet decomposition

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Wavelet packet decomposition (WPD) (sometimes known as just wavelet packets) is a wavelet transform where the signal is passed though more filters than the DWT.

In the DWT, each level is calculated by passing the previous approximation coefficients though a high and low pass filters. However in the WPD, both the detail and approximation coefficients are decomposed.

For n levels of decomposition the WPD produces 2ⁿ different sets of coefficients (or nodes) as opposed to (n + 1) sets for the DWT. However, due to the downsampling process the overall number of coefficients is still the same and there is no redundancy.