[gmpi] Re: ramped parameters

  • From: Mike Berry <mberry@xxxxxxxxx>
  • To: gmpi@xxxxxxxxxxxxx
  • Date: Wed, 05 Jan 2005 14:13:04 -0700

ben wrote:

On Wednesday 05 January 2005 2:08 am, FreeLists Mailing List Manager wrote:

This
means that every DAW operator in existence is used to hearing the
effect of a plugin some time after the change shown on our monitor.


I appreciate you guys (Paul and Olaf) trying to set me straight here, but I think I was misunderstood (poor terminology on my part)


What I was saying is that if you have a "linear control event" written into a DAW automation track, the effect on the audio has a high likelihood of not being heard where it is drawn on the waveform because the underlying plugin will probably interopolate from the last value to the new value, and it can only do this AFTER it receives the new value. This is to avoid clicks (yes, I know some volume automation is applied directly to the waveform ..... but this is a host function, generally not a plugin automation issue ) ( and yes, I'm sure many plugins don't ramp their values but I think most do. )

What I'm saying is that even if you draw a controller change at X samples, don't be naive enough to think that you are doing "sample accurate changes". The only way this could be implemented correctly is if the host asks the plugin "how far ahead should I send you this parameter change so that the full effect is heard by sample X" which I think we can agree is overkill.

I can't speak for all DAWs but this is not how Premiere handles it for VST plugins. We interpolate between automation points and update the plugin parameters every buffer, and the buffers are very small. With GMPI, we would do exact interpolation. So the plugin specifically should NOT be adding its own interpolation layer. We know the future, and we will make sure that the plugin gets the right data. The same should be the case for live controls (though, of course, we don't know the future). Any interpolation should be handled by the host (We have lots of interpolation modes besides linear). The plugin should simply respond exactly to the events that it is passed.


--
Mike Berry
Adobe Systems

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