The phase shift test from my previous mail expresses quadrature transformer output as normalized instantaneous frequencies (cycles). Depending on frequency (within the working range), deviation can be up to 1/100 of a cycle both for [olli~] and Pd's [hilbert~]. Of those two, [hilbert~] may even be most accurate, but [olli~]'s working range extends two octaves lower.
The question is what accuracy and range you need per application, and how audible deviations are in practice. Would be nice to have a catalog of quadrature transformers (in Pd abstraction) for testing and prototyping, including Csound's. Katja On Fri, Jun 24, 2016 at 3:47 AM, Alexandre Torres Porres <por...@gmail.com> wrote: > I guess I have to find a way to implement it and test it. > > By the way, I'm testing max's hilbert~ with olli's - find picture attached. > > is this a good way to test it by the way? Seems Max's is more accurate > > > > 2016-06-23 22:40 GMT-03:00 Matt Barber <brbrof...@gmail.com>: >> >> Not sure. I've used csound's a lot in ambisonic decoding and it's always >> worked well. >> >> On Thu, Jun 23, 2016 at 6:06 PM, Alexandre Torres Porres >> <por...@gmail.com> wrote: >>> >>> olli's seems easier for me to code, and better than csound's huh? >>> >>> thanks >>> >>> 2016-06-23 11:27 GMT-03:00 Matt Barber <brbrof...@gmail.com>: >>>> >>>> csound's hilbert transform is also 6th-order. Code here: >>>> >>>> >>>> https://github.com/csound/csound/blob/2ec0073f4bb55253018689a19dd88a432ea6da46/Opcodes/ugsc.c >>>> >>>> On Thu, Jun 23, 2016 at 9:16 AM, katja <katjavet...@gmail.com> wrote: >>>>> >>>>> Attached is a zip with test patch for [olli~] and [hilbert~] so you >>>>> can compare and also check with different sample rates. It seems that >>>>> Olli's coefficients are optimized to work well from 20 Hz up at 44K1 >>>>> sample rate, and Pd's built-in from 80 Hz up. They both work at other >>>>> samples rates too, but with different range. >>>>> >>>>> Since the coefficients for x[n-2] and y[n-2] are non-zero in the >>>>> biquads, the maximum phase shift is as large as in any 2nd order >>>>> section, therefore I think the four sections together are 8 order >>>>> equivalent indeed. >>>>> >>>>> By the way, the abstraction in my first response wasn't completely >>>>> vanilla-compatible, this is fixed in current attachment (for anyone >>>>> else interested). >>>>> >>>>> Katja >>>>> >>>>> On Thu, Jun 23, 2016 at 6:24 AM, Alexandre Torres Porres >>>>> <por...@gmail.com> wrote: >>>>> > Awesome, I can code it based on that :) but which order is it? >>>>> > >>>>> > I see it has 4 biquads, but it doesnt look like an 8th order because >>>>> > some >>>>> > coefficients are zeroed out, so I'm confused. >>>>> > >>>>> > Another question, does it work at any sample rate? This question is >>>>> > also >>>>> > aimed to pd's hilbert~ abstraction by the way. >>>>> > >>>>> > cheers >>>>> > >>>>> > 2016-06-22 17:27 GMT-03:00 katja <katjavet...@gmail.com>: >>>>> >> >>>>> >> Hi, Olli Niemitalou has coefficients published for a higher order >>>>> >> 'hilbert transformer' on http://yehar.com/blog/, attached is [olli~] >>>>> >> abstraction based on it. >>>>> >> >>>>> >> Katja >>>>> >> >>>>> >> On Wed, Jun 22, 2016 at 4:37 AM, Alexandre Torres Porres >>>>> >> <por...@gmail.com> wrote: >>>>> >> > Howdy, I'm working on a frequency shifter object (via single >>>>> >> > sideband >>>>> >> > modulation / complex modulation). >>>>> >> > >>>>> >> > In Max they have a so called "6th order hilbert transformer with a >>>>> >> > minimum >>>>> >> > of error". In Pd, the hilbert~ abstraction is 4th order. I'm >>>>> >> > copying the >>>>> >> > pd >>>>> >> > abstraction for now, but I was hoping to use such a higher order >>>>> >> > filter >>>>> >> > and >>>>> >> > also use- but I can't find a source for such a formula. Any help >>>>> >> > finding >>>>> >> > it? >>>>> >> > >>>>> >> > thanks >>>>> >> > >>>>> >> > _______________________________________________ >>>>> >> > Pd-list@lists.iem.at mailing list >>>>> >> > UNSUBSCRIBE and account-management -> >>>>> >> > https://lists.puredata.info/listinfo/pd-list >>>>> >> > >>>>> > >>>>> > >>>>> >>>>> _______________________________________________ >>>>> Pd-list@lists.iem.at mailing list >>>>> UNSUBSCRIBE and account-management -> >>>>> https://lists.puredata.info/listinfo/pd-list >>>>> >>>> >>> >> > _______________________________________________ Pd-list@lists.iem.at mailing list UNSUBSCRIBE and account-management -> https://lists.puredata.info/listinfo/pd-list
