Function: filterbankrealdual
FILTERBANKREALDUAL  Dual filters of filterbank for real signals only 
  Usage:  gd=filterbankrealdual(g,a,L);
          gd=filterbankrealdual(g,a);

  FILTERBANKREALDUAL(g,a,L) computes the canonical dual filters of g*
  for a channel subsampling rate of a (hop-size) and a system length L.
  L must be compatible with subsampling rate a as 
  L==filterbanklength(L,a). The dual filters work only for real-valued
  signals. Use this function on the common construction where the filters
  in g only covers the positive frequencies.

  filterabankrealdual(g,a) does the same, but the filters must be FIR
  filters, as the transform length is unspecified. L will be set to 
  next suitable length equal or bigger than the longest impulse response.

  The format of the filters g are described in the help of FILTERBANK.

  In addition, the function recognizes a 'forcepainless' flag which
  forces treating the filterbank g and a as a painless case
  filterbank.  

  To actually invert the output of a filterbank, use the dual filters
  together with 2*real(ifilterbank(...)).

  REMARK: Perfect reconstruction can be obtained for signals of length
  L. In some cases, using dual system calculated for shorter L might
  work but check the reconstruction error.

Url: http://ltfat.github.io/doc/filterbank/filterbankrealdual.html

See also: filterbank, ufilterbank, ifilterbank.

Package: ltfat