[mirtoolbox] Re: mircepstrum delays
- From: Olivier Lartillot <olartillot@xxxxxxxxx>
- To: mirtoolbox@xxxxxxxxxxxxx
- Date: Fri, 24 Sep 2010 14:46:15 +0300
Hi Hendrik and List,
This is a very pertinent question. I propose to update the explanation of
mircepstrum options in the User's Manual as follows:
> mircepstrum(..., ‘Min', min) specifies the lowest delay taken into
> consideration, in seconds. Default value: 0.0002 s (corresponding to a
> maximum frequency of 5 kHz). This default value is not set to 0 s in order to
> exclude the very high peaks confined in the lowest quefrency region: these
> high peaks seem to come from the fact that the spectrum is a non-centered
> signal, thus with high (quasi-)stationary energy. However, the value can be
> forced to 0 using this ‘Min’ option.
> mircepstrum(..., ‘Max', max) specifies the highest delay taken into
> consideration, in seconds. Default value: 0.05 s (corresponding to a minimum
> frequency of 20 Hz). This default value is not set to Inf in order to exclude
> the very high peaks confined in the highest quefrency region: these high
> peaks seem to come from the fact that the spectrum is a highly variable
> signal, thus with high energy on its highest frequencies. However, the value
> can be forced to Inf using this ‘Max’ option.
Would this be correct and clear?
As you can see, I also change the default value of Min, now set to 0.0002 s. I
found that empirically trying with some audio signal. But if you know some
specific default values we could set, please tell me.
Regards,
Olivier
Hendrik Schreiber kirjoitti 17.9.2010 kello 12.50:
> Hi Guys,
>
> I'm currently looking at the mircepstrum code and have a couple of questions:
>
> The documentation says, the min delay is 0s - the code says it's 0.0005s - I
> guess that's a (documentation) bug, right?
>
> I'm unfortunately not very familiar with cepstrums - is there some literature
> (you could point me to) that explains why I would like to use delays when
> creating the cepstrum rather than when interpreting it? This might also be a
> nice addition for the docs/code-comments.
>
> Also, I'm wondering, why does one want to specify a max delay? Isn't that
> given through the sample frequency and the size of the window?
>
> Thanks a lot for your insights,
>
> -hendrik
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