How to define delay alignment values using DWT and IDWT via Simulink?

Hello, I'm using DSP system toolbox - multirate filters - Dyadic Analysis Filter Bank. After simple decomposition and reconstruction, I use FFT scope to view the spectrum. But I've got aliasing effect, I'm sure that's because of missing alignment to each subband.

In an example of Haar wavelet 3 decomposition levels, the delays applied to each subband are -3 -1 0 0 respectively (details to average). The result is that there's no aliasing effect.

But the problem is, when I use e.g. Daubechies D4 (Filter is Daubechies, wavelet order is 4 ), how to calculate the corresponding delays? Perhaps it has something to do with filter length.

Another problem: when Filter is Daubechies and wavelet order is 3, that's also possible! But in mathematics the Daubechies wavelet order should be even number only! Could anyone explain this?

Thanks a lot!!

Answer 1

[Jichun]

Problem solved. In Matlab, e.g. Daubechies with oder 1 represents Haar wavelet; Daubechies with order 2 represents Daubechies D4 actually, and so on.