How to implement Daubechies db4 from scratch in Matlab

Is there any link to find Daubechies DB4 impliment from scratch in matlab?

[Sharmin Kibria]

Can you clarify the question a bit more? Are you looking for lifting steps or the filters for db4?

Answer 1

[prabhat kumar sharma]

Hi Sudhir,

You are trying to implement the Daubechies db4 wavelet from scratch in MATLAB can be a great learning experience, there are readily available implementations that can save your time and effort. Here are your options:

• Signal Processing Toolbox: The Signal Processing Toolbox comes with built-in functions for various wavelets, including daubechies2 and daubechies4 that implement db2 and db4 wavelets, respectively. These functions provide efficient wavelet transform and inverse transform capabilities.
• Wavelet Toolbox: If you need more advanced wavelet functionalities, consider the Wavelet Toolbox. It includes a broader range of wavelets and offers detailed tools for wavelet analysis, synthesis, and denoising.

Here is the basic minimal implementation idea of db4 wavelet decomposition:

function [cA, cD] = db4_wavelet_decompose(signal) 
    % Daubechies db4 wavelet decomposition 
    % signal: Input signal to decompose 
    % db4 decomposition low-pass and high-pass filter coefficients 
    Lo_D = [0.2303778133088964, 0.7148465705529154, 0.6308807679298587, ... 
           -0.0279837694168599, -0.1870348117190931, 0.0308413818355607, ... 
            0.0328830116668852, -0.0105974017850690]; 

    Hi_D = [-0.0105974017850690, -0.0328830116668852, 0.0308413818355607, ... 
             0.1870348117190931, -0.0279837694168599, -0.6308807679298587, ... 
             0.7148465705529154, -0.2303778133088964]; 
    
    % Convolve signal with low-pass and high-pass filters 

    cA = conv(signal, Lo_D, 'same'); 
    cD = conv(signal, Hi_D, 'same'); 
     
    % Downsample the convolved signals 
    cA = cA(1:2:end); 
    cD = cD(1:2:end); 
end 

Here are few relevant resources might be useful for you:

https://mathworks.com/products/wavelet.html

https://mathworks.com/help/wavelet/ref/dbaux.html

I hope it helps!