sfb_sym.m

Double Density Wavelet Soft

function y = sfb_sym(lo, bp, hi, sf)

% SYNTHESIS FILTER BANK
%    with symmetric extension
% y = sfb_even(lo, bp, hi, sf)
% INPUT
%   lo : lowpass subband signal
%   bp : bandpass subband signal
%   hi : highpass subband signal
%   sf : synthesis filters
% OUTPUT
%   y  : output signal

g0 = sf{1};
g1 = sf{2};
g2 = sf{3};

N = 2*length(lo);

% lowpass subband
A = length(g0)/2;
k = 0:A-1;
lo = [lo(A-k) lo lo(N/2-k)];    % symmetric extension
lo = up(lo,2);                  % upsample
lo = conv(lo,g0);               % filter
lo = lo(3*A-1+[1:N]);           % extract valid part

% bandpass subband
A = length(g1)/2;
k = 0:A-2;
bp = [bp(A-k) bp bp(N/2-k)];    % symmetric extension
bp = up(bp,2);                  % upsample
bp = conv(bp,g1);               % filter
bp = bp(3*A-2+[1:N]);           % extract valid part

% highpass subband
A = (length(g2)+1)/2;
k = 0:A-1;
hi = [hi(A-k) hi hi(N-k)];      % symmetric extension
hi = conv(hi,g2);               % filter
hi =  hi(2*A+[1:N]-1);          % extract valid part

% add signals
y = lo + bp + hi;