Process_resample

matisu13 · July 22, 2020, 1:53am

Hi Francois,
does the resample function in brainstorm can avoid Signal aliasing? How does it work?

I get so many example in the functions? What are the differences between these usage? By the way, where can I get tutorial (I just search the Brianstorm Website)?
Hope you everything goes well

Francois · July 23, 2020, 1:55pm

I'm sorry, there is no advanced documentation for the resample function, beyond the documentation in the code itself. The method used by default is 'resample-cascade'.

github.com

brainstorm-tools/brainstorm3/blob/master/toolbox/process/functions/process_resample.m#L192


    % Time = linspace(Time(1), Time(end), size(x,2));
    Time = Time(1) + (0:(size(TFout,2)-1)) ./ NewFreq;
end




%% ========================================================================================
%  ====== RESAMPLING FUNCTIONS ============================================================
%  ========================================================================================


%% ====== RESAMPLE-CASCADE =====
% USAGE: [x,Pfac,Qfac] = process_resample('ResampleCascade', x, NewRate, OldRate, Method)
% INPUT:
%     - x       : Signal to process [nChannels x nTime]
%     - NewRate : New sampling frequency (Hz)
%     - OldRate : Original sampling frequency (Hz)
%     - Method  : 'resample' or 'decimate'
% OUTPUT:
%     - x    : Resampled signal
%     - Pfac : Array of successive upsampling factors
%     - Qfac : List of successive downsampling factors
% NOTE: Requires Signal Processing Toolbox

You can use the function "test_resample.m" to evaluate the difference between these methods.

github.com

brainstorm-tools/brainstorm3/blob/master/toolbox/script/test_resample.m

function [a, time_in, time_out, el] = test_resample(a_init, sfreq_out, sfreq_in)
% TEST_RESAMPLE: Test all the methods available in Brainstorm for resamlping.
% 
% USAGE:  test_resample(a_init, sfreq_out, sfreq_in)
%         test_resample(a_init)
%         test_resample()
%         [a, time_in, time_out, el] = test_resample();
%
% INPUT: 
%     - a_init    : Signal to resample
%                   Default: [cos(t);sin(t)], with t=-pi:.0001:pi
%     - sfreq_out : Output sampling frequency
%                   Default: 4217
%     - sfreq_in  : Initial sampling frequency
%                   Default: 5000
%
% OUTPUT:
%     - a        : Cell-array oo the resampled signals for each method
%     - time_in  : Input time vector (scalar)
%     - time_out : Resampled time vector for each method

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matisu13 · July 24, 2020, 1:30pm

Thanks, Francois. It helps a lot