[LAD] Plugin buffer size restrictions

Fons Adriaensen fons at linuxaudio.org
Mon May 28 17:01:47 UTC 2012

On Mon, May 28, 2012 at 06:05:20PM +0300, Stefano D'Angelo wrote:
> IMO it's easily said: if control rate < audio rate it's plugin's
> responsibility, otherwise the host feeds upsampled/filtered control
> signals at audio rate to the plugin and all problems evaporate...

The don't evaporate, they explode.

Take a filter plugin. Calculating the actual filter coefficients
from the 'user' parameters (frequency, gain, etc..) can easily be
10..1000 times more complex than actually using those coefficients
to process one sample. So you really don't want to do that at the
audio sample rate. A normal EQ as used in a DAW could do this once
every 10 ms or so and use simple linear interpolation in between.
And even that doesn't mean the filter should accept arbitrary 
'user' parameters on each such update - these have to be rate
limited first as well. 



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