[CLAM] clam descriptors computation

[Vegard Sandvold]

Hi,

I have some concerns about descriptors computation in CLAM-0.7.0.

First of all, segment audio descriptors are not computed when
SegmentDescriptors::Compute() is invoked. This is because the following
code snippet is missing from the ConcreteCompute() method:

        if(HasAudioD())
          GetAudioD().Compute();


Secondly, some of the spectral descriptors are not computed as one may
expect. I'm thinking mainly about MagnitudeSkewness/Kurtosis, but it may
apply to other descriptors derived from central moments of the spectrum. I
discovered and reported this some time ago, maybe a year or so, after
having inspected the Stats. If I remember right, the skewness/kurtosis is
computed on spectral magnitudes _only_, and not magnitudes weighted by
frequency index.

David: I know your are re-working the descriptors computation scheme.
Maybe you have planned for these updates? I'm happy to discuss more with
you outside the list.

Sincerely,
Vegard