tfr_bounds.m

linear time－frequency toolbox

function [AF,BF]=tfr_bounds(self,win,L);
%TFR_BOUNDS  Calculate frame bounds
%   Usage:  fcond=tfr_bounds(tfr);
%           [A,B]=tfr_bounds(tfr,win);
%           [A,B]=tfr_bounds(tfr,win,L);
%
%   Input parameters:
%         tfr   : Time/frequency representation handle.
%         L     : Length of transform to consider.
%   Output parameters:
%         fcond : Frame condition number (B/A)
%         A,B   : Frame bounds.
%
%   TFR_BOUNDS(tfr) calculates the ratio B/A of the frame bounds of the
%   frame specified by tfr. The analysis window is used.
%
%   TFR_BOUNDS(tfr,win) allows you to specify whether the analysis or synthesis
%   window should be used. Setting win to 'analysis', 'a' or 1 will result in
%   the analysis window being used, and setting win to 'synthesis','s' or 2
%   will result in the synthesis window being used.
%
%   TFR_BOUNDS(tfr,win,L) or [A,B]=TFR_BOUNDS(tfr,win,L) does the same
%   assuming a transform length of L. If L is not specified, the smallest
%   possible transform length will be used. 

if nargin<1
  error('To few input parameters.');
end;

if nargin>3
  error('To many input parameters.');
end;

global TF_STORAGE;

% Verify that TF_STORAGE has been initialized
if prod(size(TF_STORAGE))==0
  error('Please run TFR_CREATE to obtain a valid handle.');
end;

if nargin==1
  win=1;
end;

switch win
  case {'analyse','a',1}
    win=1;
  case {'synthesise','s',2}
    win=2;
  otherwise
    error('Unknown window type.');
end;

% win now indicates the window to use, and 3-win will give
% the other window.
[winpos,L]=assert_winready(self,L,win,0,0,'TFR_BOUNDS');

% Unpack what we need
a=TF_STORAGE.data{self}.a;
M=TF_STORAGE.data{self}.M;
dgtinfo=TF_STORAGE.data{self}.dgtinfo;
gf=TF_STORAGE.data{self}.w{winpos}.gf;
L=L*dgtinfo.Lmul;

lambdas=comp_gfeigs(gf,L,a,M);
s=size(lambdas,1);
  
% Min and max eigenvalue.
AF=lambdas(1);
BF=lambdas(s);
  
% Possibly scale differently.  
AF=AF/dgtinfo.winscale;
BF=BF/dgtinfo.winscale;

if nargout<2
  AF=BF/AF;
end;