Merge pull request #55 from davircarvalho/master

add SOFAresample function

SOFAtoolbox/SOFAresample.m

@@ -0,0 +1,75 @@
+function Obj = SOFAresample(Obj, Fs, scale)
+% Signal resampling
+% 
+%   Description:
+%                    This function modifies the input SOFA object 
+%                    to a specified sampling rate
+%
+%   Usage:           Obj = SOFAresample(Obj, Fs)
+%
+%   Input parameters:
+%     Obj:           SOFA object with SimpleFreeFieldHRIR convention.
+%     Fs:            Desired output sampling rate
+%     scale:         Wheter or not to scale the output to have a similar 
+%                    output total energy as the input.
+% 
+%   Output arguments:
+%     Obj:           SOFA object with SimpleFreeFieldHRIR convention.
+
+% #Author: Davi R. Carvalho
+
+%% parse inputs
+if nargin < 3
+    scale = true;
+elseif nargin == 3
+    scale = boolean(scale);
+end
+
+%% Process
+Obj = SOFAconvertConventions(Obj);
+Fs_orig = Obj.Data.SamplingRate;
+IR = resample_this(Obj.Data.IR, Fs_orig, Fs, scale);
+
+%% Output
+Obj.Data.IR = IR;
+Obj.Data.SamplingRate = Fs;
+Obj = SOFAupdateDimensions(Obj);
+end
+
+% --------------------------------------------------------------------------
+function IR = resample_this(X, Fs_in, Fs_out, scale)
+    [p,q] = rat(Fs_out / Fs_in, 0.0001);
+    normFc = .965 / max(p,q);
+    order = 256 * max(p,q);
+    beta = 12;
+    %%% Create a filter via Least-square linear-phase FIR filter design
+    lpFilt = firls(order, [0 normFc normFc 1],[1 1 0 0]);
+    lpFilt = lpFilt .* kaiser(order+1,beta)';
+    lpFilt = lpFilt / sum(lpFilt);
+    lpFilt = p * lpFilt;
+
+    % Initialize output matrix
+    N_pos = size(X, 1);
+    N_ch = size(X, 2);
+    N_samples = ceil((Fs_out/Fs_in) * size(X, 3)); % length after resample
+    IR=zeros(N_pos, N_ch, N_samples);
+
+    % Actual Resample
+    for k = 1:N_pos
+        for l = 1:N_ch
+            IR(k, l, :) = resample(squeeze(X(k,l,:)), p, q, lpFilt);
+        end 
+    end
+
+    % check scaling
+    if scale
+        IR = IR.* q/p;  
+    end
+
+    % make sure signal length is not odd
+%     if rem(size(IR,3), 2) ~= 0
+%        IR(:,:,end) = []; 
+%     end
+end
+
+

SOFAtoolbox/demos/demo_SOFAresample.m

@@ -0,0 +1,66 @@
+% load Obj and resample it
+% 
+% #Author: Davi Carvalho
+% 
+% SOFA Toolbox - demo script
+% Copyright (C) Acoustics Research Institute - Austrian Academy of Sciences
+% Licensed under the EUPL, Version 1.2 or – as soon they will be approved by the European Commission - subsequent versions of the EUPL (the "License")
+% You may not use this work except in compliance with the License.
+% You may obtain a copy of the License at: https://joinup.ec.europa.eu/software/page/eupl
+% Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+% See the License for the specific language governing  permissions and limitations under the License. 
+% 
+
+clear;  clc; close all;
+
+SOFAfile=fullfile(SOFAdbPath,'database','cipic','subject_003.sofa');
+Obj=SOFAload(SOFAfile);
+
+%% Low frequency extension 
+Fs_target = 96000;
+Obj_out = SOFAresample(Obj, Fs_target);
+
+%% general properties
+fs = Obj.Data.SamplingRate;
+% HRIRs
+IR     = shiftdim(Obj.Data.IR, 2);
+IR_out = shiftdim(Obj_out.Data.IR, 2);
+% Number of samples
+N     = size(IR, 1);
+N_out = size(IR_out, 1);
+% Time vector 
+tx     = 0:1/fs:(N-1)/fs;
+tx_out = 0:1/Fs_target:(N_out-1)/Fs_target;
+% Frequency vector
+freq     = (0:N_out/2-1)*fs/N_out;
+freq_out = (0:N_out/2-1)*Fs_target/N_out;
+
+%% PLOTS
+ch = 1; % ear
+pos = 1;   % position index
+
+%%% Plot time 
+figure()
+plot(tx, IR(:,pos,ch)); hold on
+plot(tx_out, IR_out(:, pos, ch), '--','linewidth', 1.3); hold off
+xlim([0, min(N_out, N)])
+legend('original', 'resampled', 'location', 'best')
+xlabel('Time (ms)')
+axis tight
+
+%%% Plot freq
+figure()
+ori = mag2db(abs(fft(IR(:,pos,ch), N_out)));
+out = mag2db(abs(fft(IR_out(:,pos,ch))));
+semilogx(freq, ori(1:N_out/2)); hold on
+semilogx(freq_out, out(1:N_out/2), '--','linewidth', 1.3); hold off
+legend('original', 'resampled', 'location', 'best')
+xlabel('Frequency (Hz)')
+ylabel('Amplitude (dB)')
+axis tight
+
+
+
+
+
+