[PD] phase locked loop

[Claude Heiland-Allen]

Hi Charles, SImon, list,


On 27/03/2023 04:51, Charles Z Henry wrote:
> My proposed scheme and patch are to have a low freq
> 2-pole bandpass filter L below the range and a high freq bandpass
> filter H above it, so that over the 2 octave range of each bass
> string, you get one signal +90 degrees out of phase and the other with
> -90.  So, if you can find the ratio between their amplitudes, you can
> find the frequency.
>

The [hilbert~] abstraction that comes with Pd has two all-pass biquad 
filters that give outputs approximately 90 degrees out of phase from 
each other, so calling its two outputs x and y, phase can be 
approximated with atan2(y, x) and amplitude with sqrt(x^2 + y^2).
I don't know whether it works as-is for bass frequencies though - maybe 
needs a [deephilbert~] version?


Claude
-- 
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