(no subject)
(no subject)
- Subject: (no subject)
- From: Franck STAUFFER <email@hidden>
- Date: Wed, 16 Oct 2002 00:36:35 +0200
Chris,
I'm not sure I was clear enough. Maybe I should elaborate more:
ok let's say I declare my frequency parameter as:
{ "Filter Frequency" , 0 , kAudioUnitParameterUnit_Hertz , 50.0f ,
8000.0f , 1000.0f , 0 },
in my AudioUnitParameterInfo...now I launch logic, open the AU and the
generic view creates sliders for my parameters...the frequency slider
looks good, it's says it's unit is in Hz etc...but if I move the slider
at 50% i get a frequency around 4200 Hz which is good if I want that
parameter to be scaled linearly...
if now I declare is as a generic value ranging from 0.0f to 1.0f, I can
do something like that:
myScaledFreq=pow(10.0f,3.90f*fFreq)+49.0f
this curve fits my particular needs, but then logic displays only 0.0
to 1.0 values for that parameter which is normal since i haven't
declared it as a kAudioUnitParameterUnit_Hertz this time. So my
question was: how can I declare my parameter like in the second case
and be able to tell the generic view to display my scaled frequency.
Sorry to bother you again with that...
Franck
>
Franck,
>
>
Please notice that the generic view will notice that a parameter's
>
units
>
are Hertz and then do the reasonable exponential curve scaling for the
>
slider control. We provide functions AUParameterValueFromLinear()
>
and AUParameterValueToLinear() in AudioUnitUtilities.h to convert back
>
and forth in a general way between log <-> linear.
>
>
We also have the units type kAudioUnitParameterUnit_AbsoluteCents
>
which publishes a parameter explicitly with a log frequency scale.
>
kAudioUnitParameterUnit_AbsoluteCents has the interesting property of
>
corresponding to the pitch of 100 times a MIDI note number!
>
>
Chris Rogers
>
Core Audio
>
Apple Computer
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