From: James Chandler Jr ()
Date: May 8, 2008
Subject:
Re: FAQ is BAQ! - frequency shifting.
There was a 'pretty good' IIR approximation Hilbert in CSound source last time I
looked (a few years ago). Maybe still in there.
The CSound Hilbert was a digital emulation of an analog Hilbert which was
published by Bernie Hutchins in his Electronotes magazine long ago.
It sends the signal thru two legs of cascaded first-order phase shifters. The
'staggered' FC's of the two phase shifter chains, resulted in the output of one
phase shifter cascade, a pretty good approximation of 90 degrees shifted against
the other phase shifter cascade output.
But neither output had a Hilbert relationship to the original signal.
That is how it accomplished the requisite delay so it could run in realtime. One
phase shift leg was just delayed more than the other phase shift leg.
Pretty ingenious, I thought.
jcjr
> ----- Original Message -----
> From: "Charles Henry"
> To: "A discussion list for music-related DSP"
> Subject: Re: [music-dsp] FAQ is BAQ! - frequency shifting.
> Date: Thu, 8 May 2008 14:36:14 -0500
>
>
> Quick question, here. I have sometimes struggled to create a good RT
> Hilbert transform (I made a couple of pd patches that while appearing
> to be correct on the surface with relevant math behind it, but
> produces horrible phase shifts). How does one make an RT Hilbert
> transform?
--
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