Subject: Re: 3D Audio -improving HRTF filtering From: sherin tech <sherin.tech@xxxxxxxx> Date: Thu, 6 Apr 2006 16:04:40 +0530sorry, forgot to mention I am assuming M=512 ! On 4/6/06, sherin tech <sherin.tech@xxxxxxxx> 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@xxxxxxxx> 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@xxxxxxxx> > > To: "Jose Javier Lopez" <jjlopez@xxxxxxxx> > > 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@xxxxxxxx> > > >> To: <AUDITORY@xxxxxxxx> > > >> 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 > > > > > >