ADSR envelope shaping on audio file

I'm trying to apply ADSR envelope shaping to an audio file as shown below.

load handel y Fs;
N = 1.5 * Fs;
t = [0:N-1]/Fs;
x = y/Fs;

env = interp1([0 0.1 0.3 1.1 1.5], [0 1 0.4 0.4 0], t);
y = env .* x;
sound(y,Fs)

However, when performing the .* calculation, MATLAB freezes as the calculation is too large.

Could you assist in solving this problem? Thanks in advance.

[Mathieu NOE]

hi can you sahre the data file ?

[John D]

"handel" is a built in piece of audio

Answer 1

[Mathieu NOE]

hi

so finally found the bug is due to improper t (time) definition

t is supposed to span from 0 to 1.5 according to the envelope specs, and have N samples

NB : the t and env lines must both have "1.5" in common otherwise there will be error msg

from there , everything runs smooth, the env is applied to the entire audio file

N);

see below :

load handel y Fs;
N = length(y);
t = linspace(0,1.5,N); % must be consistent with env definition below : [0 0.1 0.3 1.1 1.5]
env = interp1([0 0.1 0.3 1.1 1.5], [0 1 0.4 0.4 0], t);
env = env(:);
 y = env .* y(:);
sound(y,Fs)
% 

if you want to generalize the code and make it more robust , you should consider define the interp1 arguments as vectors

and generate t according to something like :

vect1 = [0 0.1 0.3 1.1 1.5];
vect2 = [0 1 0.4 0.4 0];
env = interp1(vect1, vect2, t);

t = linspace(vect1(1),vect1(end),N);

% so improved code suggestion 

load handel y Fs;
N = length(y);

vect1 = [0 0.1 0.3 1.1 1.5];
vect2 = [0 1 0.4 0.4 0];
t = linspace(vect1(1),vect1(end),N);
env = interp1(vect1, vect2, t);

env = env(:);
y = env .* y(:);
sound(y,Fs)

[John D]

Thanks very much for your help. That solved the problem!

[Mathieu NOE]

glad it helped !

Answer 2

[Mathieu NOE]

ok

so simple problem of vector dimensions mismatch in your code

the env vector is either too short or the vector on which it is applied is too long

you have to modify one or the other

below my 2 cents suggestion, assuming N was supposed to be the number of samples extracted from the original file

also I didn't get why the line : x = y/Fs; this will simply reduce the amplitude of the output signal to almost zero

load handel y Fs;
N = round(1.5 * Fs); % why 1;5 ??
t = [0:N-1]/Fs;
% x = y/Fs;     % why ??
env = interp1([0 0.1 0.3 1.1 1.5], [0 1 0.4 0.4 0], t);
env = env(:);
x_truncated = y(1:N);   % only the first N samples of the audio file 
x_truncated = x_truncated(:);

y = env .* x_truncated;
sound(y,Fs)

[John D]

Thanks for your answer.

1.5 was the size of the envelope, and the code basically extends this to fit the size of the audio file. Is there a better way of achieving this other than truncated it? Thanks again

[Mathieu NOE]

Was the size of the envelope supposed to equal the length of the total audio file ?

if yes you simply have to correct the t (time) vector length

N = length(y) ; (and not N = round(1.5 * Fs))

[John D]

Yes, 1.5 is the initial size of the envelope, which is then scaled up to fit the length of the audio file.

I've altered the code based on your suggestion, however, I would rather not truncate the final result as then the envelope will only be applied to part of the audio.

load handel y Fs;
N = length(y);
t = [0:N-1]/Fs;
env = interp1([0 0.1 0.3 1.1 1.5], [0 1 0.4 0.4 0], t);
y = env .* y;
sound(y,Fs)

I'm still getting a similar error:

Requested 73113x73113 (39.8GB) array exceeds maximum array size preference. Creation of arrays greater than this limit may take a
long time and cause MATLAB to become unresponsive.

Do you have any ideas what's up? Thanks.