____: Re: [PD] On arrays.

[padawan12]

Remind me again what Hilbert does for us Chuck, shifts all the "negative" 
frequencies relative to its application by -pi and all the "positive"
frequecies by +pi so sin(t) -> -cos(t) and cos(t) -> -sin(t) ??
How does that give us a measure of phase change?

Any reconstruction has to be of the entire sample afaics. But if you think of
an efficient way to work locally on a small part of a file (specifically
the ending) and operating backwards samplewise turn a small time error into
a frequency error spread out to be imperceivable you have a useful piece of
software. The use would be to simply make the signal end (and start)
on a zero of known phase. Do that and editing jobs that has to be done
by hand on cut and spliced musical clips get more fun :) But anything
like that would have application in a sampler as "automatic best loop"
finder. A Roland I used to have did an autocorrelation type thing
to blend out of phase loops nicely, if I remember it worked ok for long
windows of about 2 seconds, but was rubbish for short loops. 

I always wanted to see a feature in protools, hey maybe Ardour will have
it one day... where you are trying to align two clips and you want it to
snap to the phase of the signal above (which a human can obviously see
when zoomed in enough), it just has to look at the a little bit of
the audio in each section and line them up for the most coherency at
the start of the block, right?

I digress, so Hilbert can be a phase comparator (or can be used as one)?

 
 

On Wed, 27 Sep 2006 20:26:08 -0500
"Charles Henry" <czhenry at gmail.com> wrote:

> > Just getting the zeros isn't enough, if you are out of phase it will still click
> > like a bastard.
> 
> I just thought I'd submit my half-formed analysis idea for this.... We
> can use the Hilbert transform to capture the instanteous phase of the
> signal, so we might could use it to detect phase discontinuities.  If
> so, the phase could be smoothed out by using a running average filter
> over the location of the discontinuity, and then the signal could be
> reconstructed.
> 
> Chuck
> 
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