On Monday, November 11, 2013, Urs Heckmann wrote: > > > On 11.11.2013, at 01:33, robert bristow-johnson <r...@audioimagination.com> > wrote: > > > > but you cannot define your current output sample in terms of the current > > output sample. > > > But that, with all due respect, is what has been done for quite a while. It > isn't the major ingredient of great sound, but it arguably has its perks, > albeit cpu smoking ones. > Sorry to jump in again, but I believe I can rephrase RBJs statement as "computation of the output will always require state" without loss of generality. When I first started reading up on this field, it was implied that a "zero delay filter" was a stateless y=f(x) type affair. That implication is obviously false, but somehow I was mislead into that understanding. If you hold that position and reinterpret RBJs assertion above, you can see its original sense. I've had customers ask me "do your EQs use delays?".
The answer is simply "yes, I use the correct delays for my implementation". But somewhere the idea of a stateless EQ has come into existence. iceq1 and iceq2 are exactly state variables. They just happen to be excellent topology-preserving choices of state variable. The correct question from customers should have been "do your EQs add delays that could be avoided by thinking more carefully?". Best, Dave -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
