function [RIR_cell] = ISM_RIR_bank(setupstruc,RIRFileName,varargin)
%ISM_RIR_bank Bank of RIRs using Lehmann & Johansson's image-source method
%
% [RIR_CELL] = ISM_RIR_bank(SETUP_STRUC,RIR_FILE_NAME)
% [RIR_CELL] = ISM_RIR_bank( ... ,'arg1',val1,'arg2',val2,...)
%
% This function generates a bank of room impulse responses (RIRs) for a
% particular user-defined room setup, using Lehmann and Johansson's
% implementation of the image-source method (see: "Prediction of energy
% decay in room impulse responses simulated with an image-source model", J.
% Acoust. Soc. Am., vol. 124(1), pp. 269-277, July 2008). The input
% SETUP_STRUC is a structure of enviromental parameters containing the
% following fields:
%
% Fs: sampling frequency (in Hz).
% room: 1-by-3 vector of enclosure dimensions (in m),
% [x_length y_length z_length].
% mic_pos: N-by-3 matrix, [x1 y1 z1; x2 y2 z2; ...] positions of N
% microphones (in m).
% src_traj: M-by-3 matrix, [x1 y1 z1; x2 y2 z2; ...] positions of M
% source trajectory points (in m).
% T20 or T60: scalar value (in s), desired reverberation time.
% c: (optional) sound velocity (in m/s).
% abs_weights: (optional) 1-by-6 vector of absorption coefficients weights,
% [w_x1 w_x2 w_y1 w_y2 w_z1 w_z2].
%
% If the field SETUP_STRUC.c is undefined, the function assumes a default
% value of sound velocity of 343 m/s.
%
% The field 'abs_weight' corresponds to the relative weights of each of the
% six absorption coefficients resulting from the desired reverberation time.
% For instance, defining 'abs_weights' as [1 1 0.8 0.8 0.6 0.6] will result
% in the absorption coefficients (alpha) for the walls in the y-dimension
% being 20% smaller compared to the x-dimension walls, whereas the floor
% and ceiling will end up with absorption coefficients 40% smaller (e.g.,
% to simulate the effects of a concrete floor and ceiling). If this field
% is omitted, the parameter 'abs_weight' will default to [1 1 1 1 1 1],
% which leads to uniform absorption coefficients for all room boundaries.
%
% The structure SETUP_STRUC may contain one of the two fields 'T60' or
% 'T20'. This function will automatically determine which reverberation
% type is used and compute the desired room absorption coefficients
% accordingly. T20 is defined as the time required for the impulse response
% energy to decay from -5 to -25dB, whereas T60 corresponds to the time
% required by the impulse response energy to decay by 60dB. Setting the
% corresponding field value to 0 achieves anechoic impulse responses
% (direct path only).
%
% In addition, a number of other (optional) parameters can be set using a
% series of 'argument'--value pairs. The following parameters (arguments)
% can be used:
%
% 'Delta_dB': scalar (in dB), parameter determining how much the resulting
% impulse response is cropped: the impulse response is
% computed until the time index where its overall energy
% content has decreased by 'Delta_dB' decibels, after which
% the computations stop. Not relevant if the reverberation
% time is set to 0 (anechoic case). Defaults to 50.
% 'SilentFlag': set to 1 to disable this function's on-screen messages.
% Defaults to 0.
%
% This function returns a 2-dimensional cell array RIR_CELL containing the
% RIRs for each source trajectory point and each microphone, organised as
% follows: RIR_CELL{mic_index,traj_index}. The resulting filter length
% may differ slightly in each computed RIR.
%
% This function also saves the computation results on file. The argument
% RIR_FILE_NAME determines the name of the .mat file where the variable
% RIR_CELL is to be saved. If a file already exists with the same name as
% the input argument, the user will be prompted to determine whether the
% file is to be overwritten or not. The given parameter RIR_FILE_NAME can
% be a full access path to the desired file. If no access path is given,
% the file is saved in the current working directory.
% Release date: November 2009
% Author: Eric A. Lehmann, Perth, Australia (www.eric-lehmann.com)
%
% Copyright (C) 2009 Eric A. Lehmann
%
% 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 .
VarList = {'Delta_dB' 50; % maximum attenuation in RIR computation
'SilentFlag' 0}; % set to 1 to disable on-screen messages
eval(SetUserVars(VarList,varargin)); % set user-definable variables
if length(RIRFileName)<=4 || ~strcmpi(RIRFileName(end-3:end),'.mat'),
RIRFileName = [RIRFileName '.mat'];
end
if exist(RIRFileName,'file')==2,
foo = input(' [ISM_RIR_bank] The file name passed as input already exists. Overwrite? [yes/no]: ','s');
if ~strcmpi(foo,'yes');
fprintf(' [ISM_RIR_bank] Terminating execution now (no data was saved).\n');
return
end
end
Fs = setupstruc.Fs;
room = setupstruc.room;
micpos = setupstruc.mic_pos;
straj = setupstruc.src_traj;
if isfield(setupstruc,'abs_weights'),
weights = setupstruc.abs_weights;
else
weights = ones(1,6);
end
if isfield(setupstruc,'c'),
cc = setupstruc.c;
else
cc = 343;
end
if isfield(setupstruc,'T60'),
alpha = ISM_AbsCoeff('t60',setupstruc.T60,room,weights,'LehmannJohansson','c',cc);
rttype = 'T60'; rtval = setupstruc.T60;
elseif isfield(setupstruc,'T20'),
alpha = ISM_AbsCoeff('t20',setupstruc.T20,room,weights,'LehmannJohansson','c',cc);
rttype = 'T20'; rtval = setupstruc.T20;
else
error('Missing T60 or T20 field.');
end
beta = sqrt(1-alpha);
nMics = size(micpos,1); % number of microphones
nSPts = size(straj,1); % number of source trajectory points
%-=:=- Compute RIR bank -=:=-
RIR_cell = cell(nMics,nSPts); % pre-allocate cell array
if ~SilentFlag, PrintLoopPCw(' [ISM_RIR_bank] Computing room impulse responses. '); end;
for mm=1:nMics,
X_rcv = micpos(mm,:);
for tt=1:nSPts, % compute ISM room impulse response for each source-receiver combinations
if ~SilentFlag, PrintLoopPCw((mm-1)*nSPts+tt,nMics*nSPts); end;
X_src = straj(tt,:);
RIR_cell{mm,tt} = ISM_RoomResp(Fs,beta,rttype,rtval,X_src,X_rcv,room,'SilentFlag',1,'c',cc,'Delta_dB',Delta_dB);
end
end
%-=:=- Save results into .mat file -=:=-
save(RIRFileName,'RIR_cell');
if ~SilentFlag, fprintf(' [ISM_RIR_bank] RIR bank parameter ''RIR_cell'' saved in file ''%s''\n',RIRFileName); end;