lifting Scheme Equations for sym4 dwt

I am using MATLAB’s lwt function with the Symlet 4 (sym4) lifting scheme. The documentation is unclear, and I am having trouble understanding the exact lifting equations.
Could anyone please provide the explicit equations for the five lifting steps (predict and update) and the final scaling for Sym4, including the correct indexing for each step? I need this for verification and fixed-point implementation for Hardware.
%split:
even[n] = s[2n]
odd[n] = s[2n+1]
%predict1:
odd[n] := odd[n] 0.3911 * even[n]
%update1:
even[n] := even[n] + (0.1244)·odd[n+1] + (0.3392)·odd[n]
%predict2:
odd[n] := odd[n] (1.4195·even[n] + 0.1620·even[n1])
%update2:
even[n] := even[n] + 0.4313·odd[n] + 0.1460·odd[n1]
%predict3:
odd[n] := odd[n] (1.0493·even[n+1])
%scaling:
ca[n] = K1 · even[n] with K1 = 1.5707 (approximation / low-pass)
cd[n] = K2 · odd[n] with K2 = 0.6367 (detail / high-pass)
these are the equations am currently working with but am not sure about the indexing if its causal or needs lookahead i can't determine it for each stage, the coefficients are correct they're from the Matlab output so i need your help correcting them

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R2025b

Preguntada:

el 28 de Feb. de 2026 a las 16:40

Editada:

el 28 de Feb. de 2026 a las 18:08

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