[LAU] LADSPA processing time for audio zeroes

Paul Davis paul at linuxaudiosystems.com
Sat Mar 28 14:46:39 EDT 2009

On Sat, Mar 28, 2009 at 11:39 AM, Ken Restivo <ken at restivo.org> 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.

JACK does not provide "port is silent" information. a JACK client
cannot know (without inspecting it) that the data available is all
silence. notice that silence does not imply that every sample is zero,
but zero-valued buffers do imply silence.

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