Re: 3D Audio -improving HRTF filtering

[sherin tech <sherin.tech@xxxxxxxxx>]

sorry, forgot to mention I am assuming M=512 !


On 4/6/06, sherin tech <sherin.tech@xxxxxxxxx> wrote:
> hi fred & Jose,
>
> So,
>
> If I am using rectangular window, ie, just taking M samples with a hop
> size of again M.
>
> for filtering using 128 point ( L ) filter ... I have to take Nfft >= M+L-1
>
> i took, Nfft as 1024 ... and after the convolution I get back 1024
> time samples ..
>
> which, I am doing a 50% overlap and add with the previous 1024 samples ..
>
> I am getting the o/p without any noise ..
>
> Can we avoid this overlap and add ?? (i don't think)
>
> regards,
> sherin
>
>
>
>
>
>
> On 4/5/06, Jose-Javier Lopez <jjlopez@xxxxxxxxxxx> wrote:
> > Hi Fred,
> >
> > Off course, any kind, is that I wanted to say (or rectangular windowing,
> > that is the same).
> >
> > Windowing is indicated for signal analysis and other DSP things, but not for
> > fast convolution using FFT.
> >
> > JJ
> >
> >
> > ----- Original Message -----
> > From: "Fred Herzfeld" <herzfeld@xxxxxxxxxxxx>
> > To: "Jose Javier Lopez" <jjlopez@xxxxxxxxxxx>
> > Sent: Wednesday, April 05, 2006 7:15 PM
> > Subject: Re: 3D Audio -improving HRTF filtering
> >
> >
> > > Hi Jose,
> > >
> > > I agree that a Kaiser window should not be used, in fact for any kind of
> > > accurate results no window at all shoud be used. Why did you single out
> > > Kaiser?
> > >
> > > Fred
> > >
> > > Jose Javier Lopez wrote:
> > >> Do not window input samples with kaiser !!!!!!!!!!!!!!!!!!!
> > >>
> > >> Review overlap-add or overlap-save algorithm in "Oppenheim -
> > >> Distrece-Time Signal Processing".
> > >>
> > >> or look for code examples on Internet.
> > >>
> > >> JJ
> > >>
> > >>
> > >> ----- Original Message ----- From: "sherin tech" <sherin.tech@xxxxxxxxx>
> > >> To: <AUDITORY@xxxxxxxxxxxxxxx>
> > >> Sent: Wednesday, April 05, 2006 11:38 AM
> > >> Subject: [AUDITORY] 3D Audio -improving HRTF filtering
> > >>
> > >>
> > >> Hi all,
> > >>
> > >> I am working on 3D-Audio based on HRTF filtering.
> > >>
> > >> My starting point is KEMAR data from MIT media labs, done by bill
> > >> gardner and Keith Martin.
> > >>
> > >> I have implemented a basic by referering to the demo SGI code provided
> > >> in MIT site.
> > >>
> > >> My first implementation is just time domain convolution , which works
> > >> wothout any noise.
> > >>
> > >>
> > >> But for efficient implementation I am trying to move to frame based
> > >> processing, as in the SGI code provided in the MIT website.
> > >>
> > >> the steps involved in my new implemantation are ...
> > >>
> > >> 1) take 1024 number of samples.
> > >> 2) Window those 1024 samples. (for this I am now using kaiser window of
> > >> beta=16)
> > >> 3) Take 1024 point FFT the input
> > >> 4) Zero pad the 128 point HRTF filter to make it 1024 point.
> > >> 5) Take 1024 FFT of HRTF Left ans Right data.
> > >> 6) Multiply the spectrum in frequency domain.
> > >> 7) Take 1024 point IFFT of the resultant spectrum.
> > >> 8) Do a 75 % overlap and add.
> > >>
> > >>
> > >> But a minor amout of noise is present in the o/p ....
> > >>
> > >> As a general instruction ... how can I improve the SNR of the o/p ?????
> > >>
> > >> I have tried , diferent type of windows, and overlap of 50 % also ..
> > >>
> > >> Any lights in to this ... ????
> > >>
> > >> regards,
> > >> sherin
> > >>
> > >>
> > >>
> > >
> > >
> > > --
> > > Fred Herzfeld, MIT '54
> > > 78 Glynn Marsh Drive #59
> > > Brunswick, Ga.31525
> > > USA
> > >
> >
>