Hi Edgar.

The paper I mentioned is here:


and it cites this paper a lot which gave me clues to what's going on:


Thanks. Mark.

-----Original Message-----
From: edgar-rft@web.de
To: Discussion of developing Nyquist plug-ins for Audacity <audacity-nyquist@lists.sourceforge.net>
Sent: Sun, Jun 28, 2009 1:05 am
Subject: Re: [Audacity-nyquist] Is there a signed version of snd-maxsamp or absolute minimum function for sound?

 > Edgar wrote in a former mail:
> You can "invert" a sound (make the negative samples become positive
> and vice versa) by using Nyquist "scale" or "mult" with a factor
> of "-1".

> Thank you but this doesn't work. See my response to Roger.

Sorry, I was cleaning up my mailbox and hadn't realized that Roger
already had answered before.

> All my original audio signals s have absolute amplitudes
> less than 1 so the energy waveform of s is always negative.

I assume you're talking about "normalized float" samples (like used
in Nyquist and Audacity) with maxPeak=1.0, minPeak=-1.0, what leads
to absolute peak values between min=0.0 and max=1.0, so lg(absPeak)
is always negative.

One of the first things I would try whould look like this:

(scale -1 (s-log (s-abs sound)))

> That's a part of the energy normalization they were referring to
> and had me scratching my head way the formula gave only zero and
> negative values.

Who is "they"? Can you tell what document? Is it one of the
CCRMA/JOSIII papers? I wasn't able to find out by reading the
mails from last week.

In Nyquist you often have to "compute around the corner", so maybe
we need to re-arrange the formula, but therefore I would need the
complete context of the original paper.

Other ideas: In Nyquist there is e.g. "snd-avg", which can compute
the RMS-power of blocks of samples.

- edgar

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