Forums

Resampling with minimum delay

Started by Vladimir Vassilevsky October 26, 2011
On Wed, 26 Oct 2011 17:07:56 -0700, Greg Berchin wrote:

> On Oct 26, 6:15&nbsp;pm, Tim Wescott <t...@seemywebsite.com> wrote: > >> The Wiener filter optimizes for least squares. &nbsp;It's very much like the >> asymptotic solution to a Kalman filter. > > Got it. It's been a long time since I studied them. I have this vague > memory that a least-squares solution with a Gaussian distribution *is* > the maximum likelihood solution. I could be mistaken. > >> > PS Tim, are you the same Tim Wescott who occasionally shows up in the >> > Control Line Stunt Forumhttp://www.stunthanger.com/smf/? >> >> Yes -- I don't recall seeing you on there: do you have a nym, or are >> you just a lurker? > > I visit the site occasionally, but have never registered. In my younger > days I was capable of the entire AMA Precision Aerobatics pattern > (though I never competed), but it's been 35 years since I did a > wingover. To put it into perspective, the last stunt plane that I flew > was powered by a Fox .35!
I have yet to do the complete pattern, ever. I was working up to it in my late teens, but then college happened, and marriage, and kids, and I never got the time until recently to pick up the reins again. I started competing last October, flying the beginner's pattern. I can do every maneuver of the real thing, but haven't put them all together in one flight yet. I might have done one today, but for breaking the plane. It's a good thing I was flying over soft ground. (To complete my day I was flying a friend's 1/2A Ringmaster on a very sick engine and poorly adjusted controls. The flight involved a lot of quick yanks backward on the handle; it ended when I went over backward onto my head. I've never gotten whacked hard enough to see a white flash before; I don't think it's necessary to my future happiness to do it ever again. At any rate, when I opened my eyes and looked around my buddies were gathered around the plane, making sure that it was in good shape. It's a _really good_ thing I was flying over soft ground today.) -- www.wescottdesign.com
Greg Berchin  <gjberchin@charter.net> wrote:

>Since you have the past signal of infinite duration, I suspect that >the least-squares optimal solution would be an ideal lowpass filter >applied to the digital signal interpreted as an analog impulse train. >Tough to implement, though, and not exactly low-delay.
Doesn't this usually come down to being identical to the Lagrangian interpolator (which is the first approach I would have used). Steve
On 26 Okt., 18:06, Vladimir Vassilevsky wrote:
> I had to resample a signal with requirement of minimal processing delay. > So I made a Lagrange polynomial extrapolator to predict the signal on > the duration of +1 sample into the future. That is straightforward and > it works good enough for the job. > However what could be the other options for extrapolation of the Nyquist > bandlimited signal? What is an optimal solution for this case?
Wouldn't be that _equivalent_ to - not extrapolating at all - using a _different_ lowpass filter ?! (assuming linear extrapolation) It seems to me that you'd be better off _directly_ designing the appropriate lowpass filter that suits your needs w.r.t. a low group delay for your band of interest. SG