[mirtoolbox] Re: novelty question
- From: Olivier Lartillot <olartillot@xxxxxxxxx>
- To: mirtoolbox@xxxxxxxxxxxxx
- Date: Wed, 3 Nov 2010 15:01:47 +0200
Hi Jens,
Thanks for the interesting question, and sorry for the late reply.
The strange behavior your observed is due to the fact that you use a very small
kernel. Since it is a gaussian checkerboard kernel (gaussian meaning there that
this matrix is windowed by a 2D Gaussian), for a 5-sample wide matrix, that
kernel does not look like a checkerboard anymore so the 2D convolution
operation performed in mirnovelty gets very approximate.
With a bigger kernel, you begin to see a peak after the node you mentioned.
That particular node comes from the fact that just before the kernel is
perfectly aligned to the transition (leading to the expected peak), there is an
exaggerated mismatch between the expectation given by the kernel and what
happens actually just before the transition.
Best,
Olivier
Jens Hjortkjær kirjoitti 21.10.2010 kello 9.35:
> Hello all,
>
> I just updated to mirtoolbox 1.3.1 and I'm a little confused about the output
> of the mirnovelty function. I seem to be getting inverted novelty scores:
> high when novelty is low and vice versa
>
> Eg:
>
> fs=1000;
> t=0:1/fs:5.999;
> L=length(t);
> y=[sin(2*pi*120*t(1:L/2)) sin(2*pi*319*t(L/2:L))];
> a=miraudio(y,fs);
> mirnovelty(a,'kernelsize',5)
>
> Here I have 0 at the change, rather than 1. I don't think I had this problem
> in earlier versions. Does anyone here have an explanation for this?
>
> Cheers,
> Jens
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