FIR Cookbook?
in [DSP]
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From: Rune Allnor on 7 Dec 2006 16:26 Fred Marshall skrev: > It's pretty simple to extend the P-M approach to an arbitrary shape and > arbitrary weights. You are right. I would think a lot of people might contest a claim that P-M filter design can fit into a cookbook DIY context. The P-M algorithm requires some pretty esoteric programmig; not something a casual DSP hobbyist would be expected to handle. Rune
From: Rune Allnor on 7 Dec 2006 16:28 Ron N. skrev: > jeff227 wrote: > > Has anyone come up with a "cookbook" for simple FIR filters similar to > > RBJ's IIR cookbook? > > Here's a filter cookbook that uses a simple scaled windowed sinc > to create arbitrary single cutoff FIR filters: > > http://www.musicdsp.org/files/wsfir.h > > Basically, you get only three degrees of freedom: sample rate, > filter length, and (stop or) passband width. How can a FIR filter design newbie be expected to choose a good filter length? Rune
From: Fred Marshall on 7 Dec 2006 17:15 "Rune Allnor" <allnor(a)tele.ntnu.no> wrote in message news:1165526796.053941.302880(a)79g2000cws.googlegroups.com... > > Fred Marshall skrev: > >> It's pretty simple to extend the P-M approach to an arbitrary shape and >> arbitrary weights. > > You are right. I would think a lot of people might contest a claim > that P-M filter design can fit into a cookbook DIY context. The P-M > algorithm requires some pretty esoteric programmig; not something > a casual DSP hobbyist would be expected to handle. > > Rune Rune, Agreed. I was responding to r b-j's comment about arbitrary shapes, etc. Maybe Meteor does it but I'm not so sure it's that accessible. On the other hand, a program much like P-M could be made available as a function call that would take arbitrary shapes and weights. My question was: is this to the point and useful? The notion wasn't that a beginner should do the programming - just make the function calls. Regarding length: I've never been too keen on length estimators because iterating on length is so easy (and fast) to do under many circumstances. That and the fact that length can be estimated in a gross way as the reciprocal of the narrowest transition width. At least that estimate tells you if you are in dreamland. Fred
From: Ron N. on 7 Dec 2006 17:22 Rune Allnor wrote: > Ron N. skrev: > > jeff227 wrote: > > > Has anyone come up with a "cookbook" for simple FIR filters similar to > > > RBJ's IIR cookbook? > > > > Here's a filter cookbook that uses a simple scaled windowed sinc > > to create arbitrary single cutoff FIR filters: > > > > http://www.musicdsp.org/files/wsfir.h > > > > Basically, you get only three degrees of freedom: sample rate, > > filter length, and (stop or) passband width. > > How can a FIR filter design newbie be expected to choose a > good filter length? I suppose a nice addition to these cookbook filters would be a function to return estimates of the transition band, passband ripple, and peak stopband ripple for a given set of the 3 filter parameters plus the word size. I note that this was not done for RBJ's IIR cookbook, where the number of bits of precision can seriously affect the QOR for certain combinations of sample rate and "turning" frequency. IMHO. YMMV. -- rhn A.T nicholson d.0.t C-o-M
From: Ron N. on 7 Dec 2006 18:20
robert bristow-johnson wrote: > Ron N. wrote: > > > > Can't one just precalculate one filter and shift it about? > > yeah, probably. i presume you mean "scale" instead of "shift". (or do > you mean "shift and overlap-add" for additional features?) Both. Multiplying a sinc by a cosine in the time domain will shift the rectangle in the frequency domain, thus controlling the center frequency of the filter. Scaling the width of the sinc will set the bandwidth. Scaling the height will set the gain. IMHO. YMMV. -- Ron N. http://www.nicholson.com/rhn |