assert_tt.m

linear time－frequency toolbox

function info=assert_tt(ttype,a,M,callfun);
%ASSERT_TT  Assert transform type and parameters.

% Check validity of a and M
assert_squarelat(a,M,1,callfun);

% Must the window be real?
info.isreal=0;

% How must the window behave around the boundary:
%   0 - nothing special
%   1 - whole point even
%   2 - half point even
info.iseven=0;

% The correct a, M and to use when calling DGT, CANDUAL etc.
% These values might be overwritten later in this routine, depending
% on the type of transform.
info.a=a;
info.M=M;

% Requirements for the lattice parameters.
info.aeven=0;
info.beven=0;
info.Meven=0;
info.Neven=0;

% Should L possible be doubled?
info.Lmul=1;

% Should the windows be scaled.
info.winscale=1;

% What centerings should be used?
info.c_t=0;
info.c_f=0;
info.c_w=0;

ttype=lower(ttype);

switch ttype
    % -------- Gabor transforms --------------
  case {'dgt','idgt'}
  case {'dgtii','idgtii'}
    info.c_t=.5;
    % -------- Wilson transforms -------------
  case {'dwilt','idwilt'}
    info.isreal=1;
    info.iseven=1;
    info.M=2*M;
    info.winscale=2;
  case {'dwiltii','idwiltii'}
    info.isreal=1;
    info.iseven=2;
    info.M=2*M;
    info.winscale=2;
    info.c_t=0.5;
  case {'dwiltiii','idwiltiii'}
    info.isreal=1;
    info.iseven=1;
    info.M=2*M;
    info.winscale=2;
    info.c_f=0.5;
  case {'dwiltiv','idwiltiv'}
    info.isreal=1;
    info.iseven=2;
    info.M=2*M;
    info.winscale=2;
    info.c_t=0.5;
    info.c_f=0.5;
    % ------- Real Gabor transforms -----------
  case {'rdgt','irdgt'}
    info.isreal=1;
  %case {'rdgtii','irdgtii'}
  %  info.isreal=1;
  %  info.dgttype=2;
  case {'rdgtiii','irdgtiii'}
    info.iseven=0;
    info.c_f=.5;
  case {'ref_edgt','ref_iedgt','ref_edgt_1','ref_iedgt_1'}
    if rem(a,2)==0
      info.iseven=2;
    else
      info.iseven=1;
    end;
    info.Lmul=2;
    info.c_t=.5;
  case {'edgtii','iedgtii','edgt6','iedgt6'}
    if rem(a,2)==0
      info.iseven=2;
    else
      info.iseven=1;
    end;
    info.Lmul=2;
    info.c_t=.5;
    info.c_w=floor(a/2);
  otherwise      
    error([callfun,': ',ttype,', unknown transform type'])
end;

info.tt=ttype;