Re: [linux-audio-dev] jamin and FFT filtering

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Subject: Re: [linux-audio-dev] jamin and FFT filtering
From: Alfons Adriaensen (fons.adriaensen_AT_alcatel.be)
Date: Wed Aug 11 2004 - 18:37:06 EEST


On Wed, Aug 11, 2004 at 03:58:40PM +0100, Steve Harris wrote:

> In the meantime I'l try it with vanilla raised cosines.

I don't think this will work. There's a condition on the window
shape: if you add up all the time-shifted overlapping windows
the result must be a constant, otherwise you introduce AM.

If you do the raised cosine twice, this condition is not
satisfied. The 8x overlap will mitigate the effect, but
I don't think is usable.

The nice thing about SRRC is that if you do it twice, the
result is a raised cosine, and that will combine perfectly
with the next an previous ones if they are half an FFT length
apart. So any 2n overlap will work.

-- 
FA


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