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From: Rune Allnor on 1 Feb 2010 10:18
On 1 Feb, 12:41, "Afinko" <afi...(a)gmail.com> wrote:
> Hi,
>
> I am trying to use Kaiser-Bessel window before FFT.
> However, I am a bit confused about what is the difference between Kaiser
> and Kaiser-Bessel window.

Unless somebody comes up with very compelling arguments to
do otherwise, I'd interpret 'Kaiser-Bessel' the same way
as 'Dolph-Chebychev': Kaiser used Bessel functions to design
his window just the same way Dolph used Chebychev polynomials
to design his.

Rune
From: Richard Dobson on 1 Feb 2010 10:29
On 01/02/2010 13:36, Grant Griffin wrote:
> Afinko wrote:
>> I found a matlab code for generating "Kaiser-Bessel derived (KBD)
>> window":
>> http://www.ee.columbia.edu/~marios/mdct/mdct_giraffe.html
>> kbdwin.m
>>
>> With this function, such KBD windows can be generated:
>> http://en.wikipedia.org/wiki/File:Kbd-window.jpg
>>
>> And, these are not like the Kaiser windows (generated by kaiser.m) at
>> all:
>> http://en.wikipedia.org/wiki/File:KaiserWindow.jpg
>>
>> Which means, that at least, "Kaiser" and "Kaiser-Bessel derived" windows
>> are not the same.
>
> Sorry about that. Can you tell us the advantage of the Kaiser window
> over the Kaiser-Bessel window?
>

The picture referenced above shows some (relatively) strange-looking
windows; one looks like a gothic arch, the others with increasing
amounts of flat-topness. That is definitely different from a "classic"
Kaiser window which with the right param can be made to closely
approximate Hann, Gaussian, etc.

Richard Dobson

From: Vladimir Vassilevsky on 1 Feb 2010 11:28


Afinko wrote:

>>Sorry about that. Can you tell us the advantage of the Kaiser window
>>over the Kaiser-Bessel window?
>>
>>Grant
>
>
> Well, I have no idea what is the difference between "Kaiser",
> "Kaiser-Bessel", or "Kaiser-Bessel derived" window. I am totally confused.
> But I found in few papers, that "Kaiser-Bessel derived" window is commonly
> used in Advanced Audio Coding (AAC) codec.
>
> Is there someone, who is clear in this topic?

KBD window is Kaiser window modified in the way so overlapped DCT would
be invertible.

http://en.wikipedia.org/wiki/Modified_discrete_cosine_transform
http://en.wikipedia.org/wiki/Kaiser_window#Kaiser-Bessel_derived_.28KBD.29_window


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
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