Subject: Re: [linux-audio-dev] LADSPA::runAdding()
From: Juhana Sadeharju (kouhia_AT_nic.funet.fi)
Date: Fri Mar 31 2000 - 08:16:30 EEST
>From: Erik Steffl <esteffl_AT_pbi.net>
>
>pre-calculate data (values of sin or whatever) to get a performance
>boost... I guess you would want to do this in some audio plugins too...
>or is there a separate plugin init function?
This all is done at the same time than reserving memory for the plug-in.
It could happen that we need to change the table on-the-fly. The new
table is calculated in different thread than in the audio thread.
But then plug-in should provide two functions -- it can be introduced
in later versions of LADSPA.
> also, doesn't the delay start processing before it outputs anything?
The silence is in the memory already. Delay can work one sample in, one
sample out manner.
But, it could happen a plug-in reads input without outputting anything
for a while. Even a delay could work like this specially if the system
uses timed buffers to deliver the audio.
> some plugins might only output something when something special in
>input happens (like the amplitude of certain frequency is above some
>value)...
And they could output zero at meanwhile. But it depends on how the system
is implemented.
How about a disk recorder plug-in which upon button press saves
previous 10 seconds to disk and all upcoming audio. This is handy
if you miss the beginning.
I think the point is that a plug-in can read input while not outputting
anything. And can output more than is read for a given time-period.
All these can be circumvented by making the host to do them, but that
is sort of moving the problem to later. What I want is that I can
build a working system from plug-ins alone -- like building something
from Lego bricks without a need to mold even the base block for my
building.
Juhana
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