Segment audio file using time

I have a .wav file ( song.wav ) that is 5s long, I have time_start= 3.23s and time_end=4.35s and another sing.wav that is 4s long with time_start1=2.38s and time_-end1=3.56s. I want to store the segments of song.wav and sing.wav that start respectively are time_start and time_start1 and end at time_end and time_end1 into a cell array. How do I start? The answer I've seen so far were cutting the file in terms of Fs, that's not it

[Mathieu NOE]

hello Melissa

you have to do the computation on samples , and you have to know the sampling frequency FS for each wav file

you get this info when you use audioread or wavread

[Y,FS,NBITS]=wavread(FILE) (older matlab)

or

[Y,FS,NBITS]=audioread(FILE) (newer matlab)

then determine start and stop indexes , knowing the start and stop times

song1_start_ind = round(start_time*FS); % must be an integer value

song1_stop_ind = round(stop_time*FS); % must be an integer value

then

song1_extract = song1(song1_start_ind:song1_stop_ind);

do the same on the second wav file :

song2_extract = song2(song2_start_ind:song2_stop_ind);

to save to a cell array :

C{1} = song1_extract;

C{2} = song2_extract;

[Mario Malic]

Hi Mathieu,

It would be great if you post this in an answer section.

[Mathieu NOE]

will do !

tx

Answer 1

[Mathieu NOE]

hello Melissa

you have to do the computation on samples , and you have to know the sampling frequency FS for each wav file

you get this info when you use audioread or wavread

[Y,FS,NBITS]=wavread(FILE) (older matlab)

or

[Y,FS,NBITS]=audioread(FILE) (newer matlab)

then determine start and stop indexes , knowing the start and stop times

song1_start_ind = round(start_time*FS); % must be an integer value

song1_stop_ind = round(stop_time*FS); % must be an integer value

then

song1_extract = song1(song1_start_ind:song1_stop_ind);

do the same on the second wav file :

song2_extract = song2(song2_start_ind:song2_stop_ind);

to save to a cell array :

C{1} = song1_extract;

C{2} = song2_extract;

[Melissa Ette]

Thank you so much! How would this work in a loop? I am now trying to do it for a bigger sample

Answer 2

[Mathieu NOE]

hi

this is waht i suggest to do on one single wav file

if it matches your request , the main code can be converted to a function , then you can also create a loop for looping through multiple wav files in your directory. Let me know if this is also of interest for you.

so for the time being, single file / multiple extracts demo :

[song,FS,NBITS]=wavread('demo.wav');  %(older matlab)
% or 
% [Y,FS,NBITS]=audioread(FILE); %(newer matlab)

% create list of start / stop time indexes 
start_time = [1; 2 ; 3 ; 4];        % length is equal of nb of extracts 
stop_time =  [5; 6 ; 7 ; 9];

%  main loop % 

for ci = 1:length(start_time)
    % determine start and stop indexes , knowing the start and stop times
	song_start_ind = round(start_time(ci)*FS); % must be an integer value 
	song_stop_ind = round(stop_time(ci)*FS); % must be an integer value 
    % then extract
	song_extract = song(song_start_ind:song_stop_ind);
	% save to a cell array : 
	C{ci} = song_extract;
    
%     % check (plot)
%     figure(ci) , plot(song_extract);

end