Function: filterbankdual
FILTERBANKDUAL  Dual filters
  Usage:  gd=filterbankdual(g,a,L);
          gd=filterbankdual(g,a);
          

  FILTERBANKDUAL(g,a,L) computes the canonical dual filters of g for a
  channel subsampling rate of a (hop-size) and system length L.
  L must be compatible with subsampling rate a as 
  L==filterbanklength(L,a). This will create a dual frame valid for 
  signals of length L. 

  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
  such that L=filterbanklength(gl_longest,a).

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

  In addition, the funtion 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 the IFILTERBANK function.

  REMARK: In general, 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/filterbankdual.html

See also: filterbank, ufilterbank, ifilterbank.

Package: ltfat