Re: AU parameter display flags

• Subject: Re: AU parameter display flags
• From: William Stewart <email@hidden>
• Date: Mon, 14 Feb 2005 16:19:12 -0800
• Delivered-to: email@hidden
• Delivered-to: email@hidden

So I've just been working on an AU that provides no custom view and using the display AU parameter flags for a few parameters, a feature which was added due to my ceaseless nagging ;-), and now I notice that a few of them have actually been implemented in the inverse fashion. Or at least the inverse of what I had suggested. I'm not sure if this is just a straight-up bug in the AudioUnitToolbox code, or intentional (and just different than what I would have thought would be intended), so I was wondering if anyone knows which is the case.

Specifically, I am talking about these display options:
kAudioUnitParameterFlag_DisplaySquareRoot
kAudioUnitParameterFlag_DisplaySquared
kAudioUnitParameterFlag_DisplayCubed
kAudioUnitParameterFlag_DisplayCubeRoot

Rather than try to explain what I expect, I will just show what I would have thought the math might look like:


Float32 AUParameterValueFromLinear(Float32 inLinearValue, const AudioUnitParameter * inParameter)
{
Float32 minValue = inParameter->minValue;
Float32 valueRange = inParameter->maxValue - minValue;

switch (inParameter->flags & kAudioUnitParameterFlag_DisplayMask)
{
case kAudioUnitParameterFlag_DisplaySquareRoot:
return (sqrtf(inLinearValue) * valueRange) + minValue;

case kAudioUnitParameterFlag_DisplaySquared:
return (inLinearValue*inLinearValue * valueRange) + minValue;

case kAudioUnitParameterFlag_DisplayCubed:
return (inLinearValue*inLinearValue*inLinearValue * valueRange) + minValue;

case kAudioUnitParameterFlag_DisplayCubeRoot:
return (inLinearValue*inLinearValue*inLinearValue * valueRange) + minValue;

default:
return (inLinearValue * valueRange) + minValue;
}
}


Float32 AUParameterValueToLinear(Float32 inParameterValue, const AudioUnitParameter * inParameter)
{
Float32 minValue = inParameter->minValue;
Float32 valueRange = inParameter->maxValue - minValue;

switch (inParameter->flags & kAudioUnitParameterFlag_DisplayMask)
{
case kAudioUnitParameterFlag_DisplaySquareRoot:
return (sqrtf(inParameterValue) * valueRange) + minValue;

case kAudioUnitParameterFlag_DisplaySquared:
return sqrtf((inParameterValue-minValue) / valueRange);

case kAudioUnitParameterFlag_DisplayCubed:
return powf( (inParameterValue-minValue) / valueRange, 1.0f/3.0f );

case kAudioUnitParameterFlag_DisplayCubeRoot:
return powf( (inParameterValue-minValue) / valueRange, 1.0f/3.0f );

default:
return (inParameterValue-minValue) / valueRange;
}
}


This is what I would expect, but the behavior that I am getting has kAudioUnitParameterFlag_DisplaySquareRoot switched with kAudioUnitParameterFlag_DisplaySquared, and kAudioUnitParameterFlag_DisplayCubed switched with kAudioUnitParameterFlag_DisplayCubeRoot.


thanks,
Marc

_______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/coreaudio-api/email@hidden

This email sent to email@hidden

• Follow-Ups:
  • Re: AU parameter display flags
    • From: Marc Poirier <email@hidden>

• Prev by Date: Re: coreaudio jaguar version?
• Next by Date: Re: Tone Generation
• Previous by thread: AU parameter display flags
• Next by thread: Re: AU parameter display flags
• Index(es):
  • Date
  • Thread