hello
try this
I tested the code for mono and stereo wav files - should work even for more channels data
now please notice that I made sure to use the correct sampling rate associated with each file - in case they would differ from one file to another, the code will ensure that the total duration is correct - even though your filter would not have the same effect unless you include its coefficients computation inside the main loop (and take account of Fs);
folderInfo = dir('**/*.wav');
folderInfo1 = dir('**/*.tsv');
folderInfo2 = dir('**/*.txt');
cd ..\
addpath training_data\
% fir bandpass filter design with fc1 = 20/fs/2 and fc2 = 500/fs/2 with
% fs=4000
f = [0 0.005 0.015 0.245 0.255 1];
a = [0 0 1 1 0 0];
b = firpm(100,f,a);
% feature vector calculation
duration_target = 12.5; % seconds
for i=1:length(folderInfo)
filename = folderInfo(i).name
[x,Fs] = audioread(filename);
% signal filtering
xf = filter(b,1,x);
% main code
dt = 1/Fs;
[samples,channels] = size(x);
duration = (samples-1)*dt;
duration_ratio = duration/duration_target;
target_duration_samples = (1+duration_target*Fs);
if duration_ratio>1 % truncate
xf_out = xf(1:target_duration_samples,:);
else % do nothing or expand(by repetition and trimming
repetitions = ceil(1/duration_ratio);
xf_out = repmat(xf,repetitions,1); % duplicate (by excess)
xf_out = xf_out(1:target_duration_samples,:); % exact number of samples
end
% export to wav
filename_out = [filename(1:length(filename)-4) '_out.wav']
audiowrite(filename_out,xf_out,Fs);
end
