function [Fao,Fso] = blockframepairaccel(Fa, Fs, Lb, varargin)
%BLOCKFRAMEPAIRACCEL Precompute structures for block processing
%   Usage: F = blockframepairaccel(Fa,Fs,Lb);
%
%   [Fao,Fso]=BLOCKFRAMEPAIRACCEL(Fa,Fs,Lb) works similar to 
%   BLOCKFRAMEACCEL with a pair of frames. The only difference from
%   calling BLOCKFRAMEACCEL separatelly for each frame is correct
%   default choice of the slicing windows. Frame objects Fa,Fs will be
%   accelerated for length 2*Lb.
%
%   The following optional arguments are recognized:
%
%      'anasliwin',anasliwin  : Analysis slicing window. sliwin have to
%                                 be a window of length 2Lb or a string 
%                                 accepted by the FIRWIN function. It is
%                                 used only in the slicing window approach.
%                                 The default is 'hann'.
%
%      'synsliwin',synsliwin  : Synthesis slicing window. The same as the
%                                 previous one holds. The default is 'rect'.
%
%      'zpad',zpad   : Number of zero samples the block will be padded
%                        after it is windowed by a slicing window. Note the
%                        frames will be accelerated for length
%                        2*Lb+2*kv.zpad. 
%
%
%   Url: http://ltfat.github.io/doc/blockproc/blockframepairaccel.html

% Copyright (C) 2005-2015 Peter L. Soendergaard <peter@sonderport.dk>.
% This file is part of LTFAT version 2.1.1
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.

complainif_notenoughargs(nargin,3,'BLOCKFRAMEPAIRACCEL');
complainif_notvalidframeobj(Fa,'BLOCKFRAMEPAIRACCEL');
complainif_notvalidframeobj(Fs,'BLOCKFRAMEPAIRACCEL');

definput.flags.blockalg = {'naive','sliced','segola'};
definput.keyvals.anasliwin = [];
definput.keyvals.synsliwin = [];
definput.keyvals.zpad = 0;
[flags,kv]=ltfatarghelper({},definput,varargin);

isSliProp = ~isempty(kv.anasliwin) || ~isempty(kv.synsliwin) || kv.zpad~=0;
assert(~(~flags.do_sliced && isSliProp),...
   sprintf(['%s: Definig slicing window properties without setting the',...
            ' ''sliced'' flag.'], mfilename));

if flags.do_sliced 
   if isempty(kv.anasliwin)
      kv.anasliwin = 'hann';
   end
   
   if isempty(kv.synsliwin)
      kv.synsliwin = 'hann';
   end

   Fao = blockframeaccel(Fa,Lb,'sliced','sliwin',kv.anasliwin,...
                         'zpad',kv.zpad);
   Fso = blockframeaccel(Fs,Lb,'sliced','sliwin',kv.synsliwin,...
                         'zpad',kv.zpad);
else
   Fao = blockframeaccel(Fa,Lb,flags.blockalg);
   Fso = blockframeaccel(Fs,Lb,flags.blockalg);
end





