Re: [LAU] LADSPA processing time for audio zeroes

Am Samstag, den 28.03.2009, 16:38 -0700 schrieb Ken Restivo:
> On Sat, Mar 28, 2009 at 05:26:23PM +0100, Arnold Krille wrote:
> > Hi,
> >
> > On Saturday 28 March 2009 16:39:35 Ken Restivo wrote:
> > > When a LADSPA plugin is being sent zeroes-- i.e. when the volume of the
> > > input data is down to nothing-- is it still sucking up CPU cycles?
> > > I understand from the JACK API that anytime a client gets a callback with
> > > data, it has to drop down and deal with the data and then return, even if
> > > the data is zero. But that could be lightweight, if the data are zero, or
> > > is that very compute-intensive for the plugin?
> > > I'm trying to build an outboard effects chain in various LADSPA hosts (JACK
> > > Rack, ecasound, AMS, others... haven't settled on one yet), and when I've
> > > got that plugin's volume MIDI'ed down to zero, I'd like it to not be
> > > dominating CPU cycles at that time.
> >
> > Actually with double- (or any floating point-) resolution it is rather hard to
> > detect exact 0.0 values. And because of the variable exponent, the cpu usage
> > for numbers near zero is higher then for numbers near 1 (or any other higher
> > value). The keywords to search for are "denormal problems".
> >
> > In practice this means that while setting a volume to zero "should" give you
> > the desired effect of less cpu-usage, in fact the opposite is the case in the
> > worst case. When you are already controlling your effects via midi, why not
> > bind the "mute" or "active" (don't remember the current naming in jack-rack)
> > to a midi controller. An in-active effect shouldn't eat cpu cycles when the
> > host-author did his job right...
> >
>
> That's the reason why I was asking.
>
> There doesn't appear to be a way to bind the "Enable" button in Jack-Rack to a MIDI controller. If there were, I'd just use jack-rack and be done with the problem. But right-clicking on the button does nothing; only the faders appear to support MIDI mapping.
>
> So I was instead binding the Wet/Dry to a controller, but the processing on all the plugins enabled simultaneously was too CPU-bound.
>
> Perhaps the question I should ask is: how hard would it be to hack jack-rack to allow MIDI binding to the Enable button?
>
> -ken
>
No hack needed, simply check out the cvs version from jack-rack, it's
allready included.
cvs -z3
-d:pserver:anonymous@email-addr-hidden-rack.cvs.sourceforge.net:/cvsroot/jack-rack co
-P jack-rack

regards hermann

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Received on Sun Mar 29 12:15:01 2009