[aubio-user] Onset detection in Python

[Lukasz Tracewski]

Thanks for the change notes and other remarks! Indeed, by manipulating the parameters you mentioned I could tweak the onset detection algorithm to behave as in the alpha of aubio. Makes things easier if I can just recommend users to grab latest released version of aubio.

Cheers,
Lucas

> Date: Wed, 19 Mar 2014 18:05:50 -0300
> From: piem at piem.org
> To: lukasz.tracewski at outlook.com; aubio-user at aubio.org
> Subject: Re: [aubio-user] Onset detection in Python
> 
> On 03/19/2014 05:36 PM, Lukasz Tracewski wrote:
> >> This is fascinating. Would you mind if I prepare some short post
> >> to publish on aubio's blog?
> >
> > Not at all, I will be honoured!
> >
> > If you would like to know more about the project, I made a small
> > write-up in PDF available here:
> >
> https://github.com/tracek/Ornithokrites/blob/master/report/report.pdf?raw=true
> >
> > The project's development page: https://github.com/tracek/Ornithokrites/
> 
> excellent, I'll prepare a short post and submit it to you before publishing.
> 
> > One more question related to aubio (energy) onset detection. In my
> > early development version I was using 0.4.0alpha. Now that I switched
> > to 0.4.1 some more onsets gets detected, in this case false
> > positives. Did the algorithm get more sensitive? I tried tuning the
> > threshold but no avail. I did not notice anything particular in the
> > release notes. In the history of onsets you mention cleaning up and
> > there is also this change:
> >
> > aubio_onset_set_delay_ms(o, 50.); to: aubio_onset_set_delay(o, 4.3 *
> >  hop_size);
> >
> > So making delay dependent on hop size. I tried compiling with old
> > code, but actually got even more different results. Are there any
> > fixes that could concern energy onset detection between 0.4.0alpha
> > and 0.4.1? I was contemplating going back to alpha, but that is
> > usually not a smart idea (probably it is just coincidence that alpha
> >  works temporarily better for my training set, perhaps a matter of
> > tuning some other parameters than threshold).
> 
> I'm not sure exactly what version you had before. 'alpha' is a moving
> target: right after a release, the version number is increased, and
> ~alpha added to it. (feel free to send me a tarball of the source code
> you used for 0.4.0alpha if you want me to look at it more in details).
> 
> as far as onsets are concerns, only two changes between 0.4.0 and 0.4.1
> should affect the results:
> 
>  - i changed back the delay from 50ms to 4.3 * hop_size, because the
> peak-picking algorithms depends solely on the hop_size, not on the
> temporal resolution of the novelty function. the default value can not
> be set at a fixed time.
>  - i also changed the changed the minimum inter-onset-interval (minioi)
> from 5 * hop_size to 20ms, so that could explain some more of the
> changes you observed.
> 
> now you can set the delay and minimum IOI yourself. from python, you can
> set both these values using the following functions:
> 
>  - aubio.onset.set_delay, aubio.onset.set_delay_s, and
> aubio.onset.set_delay_ms
>  - aubio.onset.set_minioi, aubio.onset.set_minioi_s, and
> aubio.onset_set_minioi_ms
> 
> you can also get the current value of the onset object with the
> corresponding getters.
> 
> see the doc here: http://aubio.org/doc/latest/onset_8h.html
> 
> cheers, Paul
> 
> 
 		 	   		  
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