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filterbankwin.m    152 lines (131 with data), 4.2 kB

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function [g,info] = filterbankwin(g,a,varargin);
%FILTERBANKWIN Compute set of filter bank windows from text or cell array
% Usage: [g,info] = filterbankwin(g,a,L);
%
% `[g,info]=filterbankwin(g,a,L)` computes a window that fits well with
% time shift *a* and transform length *L*. The window itself is as a cell
% array containing additional parameters.
%
% The window can be specified directly as a cell array of vectors of
% numerical values. In this case, `filterbankwin` only checks assumptions
% about transform sizes etc.
%
% `[g,info]=filterbankwin(g,a)` does the same, but the windows must be FIR
% windows, as the transform length is unspecified.
%
% `filterbankwin(...,'normal')` computes a window for regular
% filterbanks, while `filterbankwin(...,'real')` does the same for the
% positive-frequency only filterbanks.
%
% The window can also be specified as cell array. The possibilities are:
%
% `{'dual',...}`
% Canonical dual window of whatever follows. See the examples below.
%
% `{'realdual',...}`
% Canonical dual window for a positive-frequency filterbank
% of whatever follows. See the examples below.
%
% `{'tight',...}`
% Canonical tight window of whatever follows. See the examples below.
%
% `{'realtight',...}`
% Canonical tight window for a real-valued for a positive
% frequency filterbank of whatever follows.
%
% The structure *info* provides some information about the computed
% window:
%
% `info.M`
% Number of windows (equal to the number of channels)
%
% `info.longestfilter`
% Length of the longest filter
%
% `info.gauss`
% True if the windows are Gaussian.
%
% `info.tfr`
% Time/frequency support ratios of the window. Set whenever it makes sense.
%
% `info.isfir`
% Input is an FIR window
%
% `info.isdual`
% Output is the dual window of the auxiliary window.
%
% `info.istight`
% Output is known to be a tight window.
%
% `info.auxinfo`
% Info about auxiliary window.
%
% `info.gl`
% Length of windows.
%
% `info.isfac`
% True if the frame generated by the window has a fast factorization.
%
% See also: filterbank, filterbankdual, filterbankrealdual
% Assert correct input.
if nargin<2
error('%s: Too few input parameters.',upper(mfilename));
end;
if ~iscell(g)
error('%s: Window g must be a cell array.',upper(mfilename));
end;
if isempty(g)
error('%s: Window g must not be empty.',upper(mfilename));
end;
definput.keyvals.L=[];
definput.flags.realtype={'normal','real'};
[flags,kv,L]=ltfatarghelper({'L'},definput,varargin);
if ischar(g{1})
winname=lower(g{1});
switch(winname)
case {'dual'}
[g,info.auxinfo] = filterbankwin(g{2},a,L);
g = filterbankdual(g,a,L);
info.isdual=1;
case {'realdual'}
[g,info.auxinfo] = filterbankwin(g{2},a,L);
g = filterbankrealdual(g,a,L);
info.isdual=1;
case {'tight'}
[g,info.auxinfo] = filterbankwin(g{2},a,L);
g = filterbanktight(g,a,L);
info.istight=1;
case {'realtight'}
[g,info.auxinfo] = filterbankwin(g{2},a,L);
g = filterbankrealtight(g,a,L);
info.istight=1;
otherwise
error('%s: Unsupported window type %s.',winname,upper(mfilename));
end;
end;
info.M=numel(g);
info.gl=zeros(info.M,1);
info.ispainless=1;
for m=1:info.M
[g{m},info_win] = comp_fourierwindow(g{m},L,upper(mfilename));
if isfield(g{m},'H')
if ~isnumeric(g{m}.H)
g{m}.H=g{m}.H(L);
g{m}.foff=g{m}.foff(L);
end;
if numel(g{m}.H)>L/a(m)
info.ispainless=0;
end;
else
info.ispainless=0;
end;
end;
info.longestfilter=max(info.gl);
info.isfac=1;
% The generated frame does not have a factorization if it is not uniform
if ~all(a==a(1))
info.isfac=0;
end;
if L<info.longestfilter
error('%s: One of the windows is longer than the transform length.',upper(mfilename));
end;