[LAU] [Zynaddsubfx-user] yoshimi bug fixes

Folderol folderol at ukfsn.org
Sat Oct 24 07:16:58 EDT 2009


On Sat, 24 Oct 2009 12:51:59 +0200
fons at kokkinizita.net wrote:

> On Sat, Oct 24, 2009 at 05:51:19PM +1300, Chris Edwards wrote:
> 
> > I used to be put off by meters that looked slow,
> > until I realised how useful RMS meters were and
> > how long the windowing time needs to be to capture
> > the bass frequencies. :)  Fons, I've been wondering,
> > though, does the update rate in jkmeter affect the
> > measurement window, or just the display rate?
> 
> It just determines how smoothly the display will appear.
> The dynamic behaviour of jkmeters (and also of the VU and
> PPM meters in jmeters) is very strictly defined. The values
> that are displayed are calculated in a way that does not
> depend on the display update rate, and (within reasonable 
> limits) also not on the Jack period size. A level meter
> would just be useless eye-candy otherwise.
> 
> There is indeed a 'window' for the RMS value, but
> don't imagine it as being rectangular, i.e. with 
> all samples having the same weight. The window is
> more like an impulse with a slightly smoothed front
> (which determines how it will react to short bursts)
> and an exponential decay. It is the impulse response
> of a critically damped 2nd order filter acting on the
> square of the signal. The controlled fallback of
> the RMS indication is not artificial (as it is for
> the peak value), it *is* the shape of the window.
>  
> > I've also been wondering what the purpose of the
> > fall-of on peak meters is.  Why not just reset the
> > peak level immediately and let it get bumped up
> > again by the signal?
> 
> Even in that case you would need a defined fallback
> rate. Lower peak levels should be shown only if they
> are not immediately following a much higher peak,
> otherwise the peak level will jump up and down all
> the time. In other words the bump-up should happen
> only if the current input is higher than the fallback
> of the previous peak. Having a visible fallback is
> easier on the eyes.
> 
> Ciao,

Very interesting information. It's fascinating how complicated something
like a 'simple' metering system is!

-- 
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.



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