Re: kAudioUnitProperty_DependentParameters
Re: kAudioUnitProperty_DependentParameters
- Subject: Re: kAudioUnitProperty_DependentParameters
- From: William Stewart <email@hidden>
- Date: Mon, 17 Oct 2005 15:08:40 -0700
On 17/10/2005, at 2:44 PM, Pavol Markovic wrote:
Sorry if I'm asking obvious, but I have yet another property which
usage is quite unclear to me:
kAudioUnitProperty_DependentParameters
The header says:
array of AUDependentParameter (read only)
For parameters marked with kAudioUnitParameterFlag_IsGlobalMeta,
any non-global dependent parameters are assumed to be dependent in
every element of their scope.
For parameters marked with kAudioUnitParameterFlag_IsElementMeta,
then its dependent parameters must all be the same scope, and are
assumed to apply only within a single element, not to other
instances of the same parameter in other elements.
If the host is asking which parameters are dependent on certain
Meta parameter, where does it pass the meta parameter id?
The ElementID of the GetProperty call - really obvious huh! :-)
And how can AU find out which meta dependent parameters host wants
to return
I don't understand - its all about you telling the host what your
dependencies are for a given meta param
- does the nonzero element value in GetProperty call mean I'm
asking for element meta?
Nope - that's the meta parameter ID.
Because I can't find it, I suspect the AU should return the array
of all parameters that are dependent on any meta parameter.
Yes - if the host finds a meta parameter, it asks the AU if it can
provide a list of parameters who are dependent on that (their values
can changes if the meta parameter's value is changed)
Parameter's meta behaviour is scoped either to global (changing it
can change anything), or Element - (changing this param will *only*
change other parameter values in that same scope/element pair).
So, the usage:
The element argument to GetProperty is used to specify the meta
parameter ID. The scope is used to specify the scope of the meta
parameterID of course.
Then you return an array of:
typedef struct AUDependentParameter {
AudioUnitScope mScope;
AudioUnitParameterID mParameterID;
} AUDependentParameter;
GetPropertyInfo of course, just returns the size of this array
(numDepParams * sizeof(AUDependentParameter))
Sorry for the obfuscation - we should have added this to the comments
in the header.
Bill
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