Apple

That makes sense, sorry about that, I was getting a bit confused by the argument names.

On that note, what does the list of AudioUnitParameterID's tell me when I call GetProperty with kAudioUnitProperty_ParameterList? Are they contextual based on the unit you are querying or are they just indexes?

-Stephen

-----Original Message-----
From: William Stewart [mailto:email@hidden]
Sent: Thursday, January 05, 2006 4:36 PM
To: Stephen Shaw
Cc: CoreAudio API
Subject: Re: Getting parameter info on StereoMixers

Parameter Info gives you meta-information about a parameter (min,
max, default values for instance). Parameters are presumed to be
consistent across all elements in a scope, so the element argument is
irrelevant (that's why we use the paramID here)

If you want to get the current value of a parameter, or set it, then
you should be looking at the AudioUnitGet/SetParameter calls.

Bill

On 05/01/2006, at 3:58 PM, Stephen Shaw wrote:

> A little more info on my question...
>
> In
> ComponentResult AudioUnitGetPropertyInfo(
>   AudioUnit             ci,
>   AudioUnitPropertyID   inID,
>   AudioUnitScope        inScope,
>   AudioUnitElement      inElement,
>   UInt32*               outDataSize,
>   Boolean*              outWritable
> )
>
> It appears that inElement typically refers to the bus id that you are
> talking about. But in the sample I found in CAAUParameter.cpp (
> CAAUParameter::Init)
> it is called with:
>     OSStatus err = AudioUnitGetProperty(au,
>                              kAudioUnitProperty_ParameterInfo,
>                             scope,
>                             param,
>                             &mParamInfo,
>                             &propertySize);
>
> Which looks like it is using the 3rd param as a parameter select
> instead of
> a bus select. If this is the case, then using the stereo mixer,
> how do you
> specify the correct parameter (volume) of the bus of the mixer (in
> this case
> 0)?
>
> Thanks,
> Stephen
>
>
> On 1/5/06 2:21 PM, "Stephen Shaw" <email@hidden> wrote:
>
>> I'm a little confused on the usage of
>> kAudioUnitProperty_ParameterInfo, I'm
>> trying to get the min / max range of the volume & Pan of the mixer
>>
>> I can get / set parameters using
>> AudioUnitGetParameter(mMixerUnit, kStereoMixerParam_Volume,
>> kAudioUnitScope_Input, theBusId,&vol);
>>
>> But with kAudioUnitProperty_ParameterInfo, how do I specify the
>> Parameter I'm
>> talking about?
>>
>> AudioUnitParameterInfo    paramInfo;
>> UInt32    size = sizeof (AudioUnitParameterInfo);
>>
>> AudioUnitGetProperty (mMixerUnit,           // AudioUnit
>>         kAudioUnitProperty_ParameterInfo,   // AudioUnitPropertyID
>>         kAudioUnitScope_Input,              // AudioUnitScope
>>         theBusId,                           // AudioUnitElement
>>         &paramInfo,
>>         &size);
>>
>> As always, any help is greatly appriciated :)
>>
>> -Stephen
>
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