I though further about the problem with changing parameter values. So what I would
like to know is what SampleCount
values are authors of plugin-host are typically using ?
E.g. SampleCount of 256 at 44100 hz would mean about 6ms between each parameter
change. If we are using values low
as this then the host could care about delivering smoth data.
I currently evaluate LADSPA to be the format for the plugins I rewrite from my
software SoundFX and there most
parameters are specified by a lowerand a upper bound + a modulation function which is
called at a lower frequency
as the audio-generating code. The modulation function always returns values between
0.0 and 1.0 which gets turned
into an alteration of the parameter between lower and upper bound. There are
modulation functions such as LFO's,
Fades, Envelopes, Sample&Hold, Envelop-Trackers (Pitch and Volume) and many more. I am
now thnking at which level
to integrate those : plugin-host level integration would be easier.
Additionally I would suggest for LADSPA V2
that we have
#define LADSPA_PORT_CONTROL_STATIC 0x10
which means that the parameter needs only to be evaluated in the
connect_port(LADSPA_Handle Instance,unsigned long Port,LADSPA_Data * DataLocation)
method and that the host *must* call this method when such a parameter has changed.
This could e.g. used for parameters such as
fft-size, filter-type, note (of a synth plugin such as 'C-3') which are unlikely to
change often and probably need several initial
calculations before further processing could be done. Such parameters would never be
interpolated !
Stefan
> On Mon, Mar 25, 2002 at 02:09:20 +0100, Stefan Kost wrote:
>
>>Additionally it introduces processing overhead, as parameters usually don't change
>that much.
>
>
> Agreed, there are definatly some parameters that can't/shouldn't be
> interpolated.
>
>>Ideas :
>>1.) What about if the host takes care about avoiding cracks due to parameter
>changes. Right after a parameter change,
>>it could call the plugin twice and then x-fade the outputs.
>
>
> Not all plugins can be xfaded to produce meaningful results, not to
> mention it doubles the cpu use, and you need two instances of the plugin,
> with the same state.
>
> The host can't reasonably do the parameter edge filtering, as it doesn't
> know what the appropriate scheme is. Sure, you could code up all the
> common schemes (and thier parameters) and express them as port metadata,
> but that seems uneccesarily complicated.
>
> - Steve
>
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