function inoutsig = scaletodbspl(inoutsig,spl,varargin)
%SCALETODBSPL  Scale a signal to have a specific SPL (in dB)
%   Usage: 
%     outsig = scaletodbspl(insig,spl);
%     outsig = scaletodbspl(insig,spl,dboffset);
%     outsig = scaletodbspl(insig,spl,'ac');
%     outsig = scaletodbspl(spl);
%     outsig = scaletodbspl(spl,[],dboffset);
%
%   SCALETODBSPL(insig,spl) scales the signal insig such that its 
%   sound pressure level (SPL) corresponds to spl (in dB). 
%   For the scaling, the AMT default level convention is used, which,
%   unless modified by the user, is SPL of 93.98 dB for an RMS of 1.
%
%   SCALETODBSPL(insig,spl,dboffset) scales the signal insig such 
%   that its SPL corresponds to spl (in dB). For the scaling, the 
%	user's level convention provided by dboffset defining the SPL 
%   for an RMS of 1.
%
%   SCALETODBSPL(spl) returns the scaling constant required to scale a signal
%   having RMS of 1 to SPL of spl (in dB), corresponding to the AMT default 
%   level convention. 
%
%   SCALETODBSPL(0) returns the reference ref used to calculate the SPL 
%   in the formula SPL = 20*log_10 (signal/ref)
%
%   SCALETODBSPL(spl,[],dboffset) returns the scaling constant required 
%   to scale a signal having RMS of 1 to SPL of spl (in dB), corresponding 
%   to the user's level convention provided by dboffset defining the SPL 
%   for an RMS of 1.
%
%   If the input is a matrix, it is assumed that each column is a signal.
%
%   SCALETODBSPL(insig,spl,'ac') does the same, but considers only the AC
%   component of the signal (i.e. the mean is removed).
%
%   References:
%     B. C. J. Moore. An Introduction to the Psychology of Hearing. Academic
%     Press, 5th edition, 2003.
%     
%
%   See also: dbspl
%
%   Url: http://amtoolbox.sourceforge.net/amt-0.10.0/doc/common/scaletodbspl.php

% Copyright (C) 2009-2020 Piotr Majdak and the AMT team.
% This file is part of Auditory Modeling Toolbox (AMT) version 1.0.0
%
% 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/>.
 
%   Author: 2021, Piotr Majdak
%   Author: Peter L. Soendergaard, 2009

% ------ Checking of input parameters ---------

definput.flags.mean={'noac','ac'};
definput.keyvals.dboffset=-20*log10(20e-6); % default: 20 �Pa = 0 dB
[flags,kv]=ltfatarghelper({'dboffset'},definput,varargin);

narginchk(1,5);

if ~isnumeric(inoutsig)
  error('%s: insig must be numeric.',upper(mfilename));
end;

% In the code below, "scaletodbspl" obtains the reference level from "dbspl"
% by calling "dbspl(1)", which will return only the offset measured in dB.

if nargin==1 || isempty(spl)
  % Special mode, only the level has been given
  spl=inoutsig;
  
  if ~isscalar(spl) 
    error('%s: spl must be a scalar.',upper(mfilename));
  end;

  inoutsig=gaindb(1,spl-dbspl(1,'dboffset',kv.dboffset));
  return;
end;


if ~isnumeric(spl) || ~isscalar(spl) 
  error('%s: spl must be a scalar.',upper(mfilename));
end;

% if (nargin<3) || (~ischar(options))
%   options='';
% end;


% ------ Computation --------------------------
if isinf(spl), 
  inoutsig=zeros(size(inoutsig)); 
else
  if isvector(inoutsig)
    inoutsig = gaindb(inoutsig/rms(inoutsig,flags.mean),...
      spl-dbspl(1,'dboffset',kv.dboffset));
  else
    % If we have a matrix, set the level for every column.
    for ii=1:size(inoutsig,2);
      inoutsig(:,ii) = gaindb(inoutsig(:,ii)/rms(inoutsig(:,ii),flags.mean),...
        spl-dbspl(1,'dboffset',kv.dboffset));
    end;
  end;
end