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 _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
