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@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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