Signal filtering

Hi :) I'd like to know how to divide a signal into frames (for example 25 ms frames) without overlapping. And how do I multiply each frame using the Hamming window?

Thanks!

Answer 1

[Wayne King]

Hi Anna, If you're using reshape you can't change the number of elements. so

x = randn(10,1);
x1 = reshape(x,5,2);

is ok, but

x1 = reshape(x,6,2);

is not.

Yes, you can use buffer to overlap your signal segments.

Note that buffer() will prepend and append zeros as necessary:

x = 1:10;
x1 = buffer(x,5,2);

[Anna]

It wooooooooooooooorks. Thank youuuuu. You're so awesome! :D

Answer 2

[Wayne King]

You have to know your sampling rate in order to know how many samples a 25-ms frame is. Here I'll assume it's 10 kHz. So 250 samples is 25 msec and there are 40 such segments in 1 second.

x = randn(1e4,1);
x = reshape(x,250,40);
ham = repmat(hamming(250),1,40);
x = x.*ham;

Each column of x is a 25 msec segment multiplied by a Hamming window.

[Jan]

I expect that "x = bsxfun(@times, x, hamming(250));" is faster than creating ham explicitely.

[Anna]

How come when I try to add in an audio signal (using wavread) and I try to reshape it, (I used 16kHz for Fs), an 'Error' shows up. It says that it should have the same number of elements.

And is it also possible to use buffer in the circumstance that I need to overlap?

Thank You!