# Why in Overlap Save Method in DSP output length comes out to be same as input length?

I know that when we do convolution of $$x(n)$$ (Length $$L$$) and $$h(m)$$ (Length=$$M$$), length of output data comes out to be $$L+M-1$$, but when we break a large sequence of data and find output using Overlap Save Method, length comes out to be same as input.

• Why do the extra $$M-1$$ points are appearing in this case?

In more expressive way, be $$y(n) = x(n)*h(n)$$:

Suppose Case 1.:

• $$x(n)$$ (length $$L$$),
• $$h(n)$$ (length $$M$$), leads to
• $$y(n)$$ (length $$L+M-1$$)

using simple linear convolution

Case 2.:

• $$x(n)$$ (length $$3L$$),
• $$h(n)$$ (length $$M$$), leads to
• $$y(n)$$ (length $$3L$$)

using the Overlap Save Method that evaluats output after breaking input in 3 equal parts of length $$L$$.

• It is not clear to me: Have you understood how the Overlap-Save method works? If you are fully understanding how Overlap-Save works, where does the question come from? Feb 19 '17 at 18:01
• Also, I had to completely restructure your question just to be able to read it. Please make sure your question is nicely structured yourself the next time. Feb 19 '17 at 18:03
• Are processors use different techniques (other than linear de-convolution) to interpret the input signal from the output response of systems.If answer is no then why output (having length L+M-1) evaluted using linear convolution is different from the output (having length same as input signal) given by overlap-save method. Feb 19 '17 at 20:37
• hotpaw2's answer explains that. You did not understand the overlap-save method if you're still asking this. Feb 19 '17 at 20:53