linuxaudio.org

On 06/26/2011 10:13 AM, pshirkey@boosthardware.com wrote:

quoted text
>> On Sat, 25 Jun 2011 16:23:29 +0200 (CEST), pshirkey@boosthardware.com

>> wrote:

>>> Hi,

>>>

>>> Can anyone point me to a simple code example for how to determine the

>>> phase at a specific time in a waveform?

>>>

>>> ex. if I have a sample that is 5 seconds long and want to know the

>>> phase

>>> at 2.5 seconds

>>>

>>> I'm open to code in any language or a scripted example if such a tool

>>> exists. If there is an ui which has that feature I am also

>>> interested.

>>>

>>

>> in general, theory i mean, phase equals delay; it can be computed

>> deterministically iif the signal is a pure tone (sinusoidal) otherwise

>> you must have a reference signal and referring to its fundamental

>> frequency (1st order harmonic) or, when in-the-field, you can pick one

>> conventional signal tone (i've been told that a 1khz is a usual choice:)

>> and compare to that.

>>

>> if you are to compare two known signals (often input vs. output of some

>> lti transformation, eg. filter), than the computation to do is

>> correlation. well, you should use fft for that, but i'm sure you know

>> that:)

>>

>

> You wouldn't happen to have an example of this code?

>

> Perhaps there is something in qtractor along these lines already?

>

no, not at all :) qtractor doesn't have anything of the sort, sorry. i

was just clearing dust from the top of my mind re. lti systems theory :)
> I have looked at integrating something with librubberband but first things

quoted text
> first right?

>

hmmm... there's this wsola algorithm for time-stretching in the

time-domain (cf. frequency-domain as in rubberband) where

auto-correlation is computed to find the optimum overlap window point

(by waveform similarity). well, that's maybe an idea spark... but again

you need the zero-phase/origin reference signal waveform anyway to

correlate to... 'coz, as others said, your question doesn't make much

sense as is :)
cheers

--

rncbc aka Rui Nuno Capela

rncbc@rncbc.org

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