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Revisited Re: AudioUnitSetParameter question
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Revisited Re: AudioUnitSetParameter question


  • Subject: Revisited Re: AudioUnitSetParameter question
  • From: "Jeremy@Verizon" <email@hidden>
  • Date: Wed, 28 Aug 2002 16:23:06 -0400

I do not understand why Reverb Room-Type is a property and not a parameter.
It seems that Room type is very specific to a particular class of plug-ins,
namely reverb. Why then is there a Room-Type property?

It would certainly make for cleaner, less special-cased code.

Also, why is there an enum type but no way to get at the strings needed to
display the meaning of the values? This seems like a missing part of the
audiounit spec. Any comments welcome.

Thanks,
Jeremy

> From: Chris Rogers <email@hidden>
> Date: Fri, 15 Feb 2002 02:58:09 -0800
> To: email@hidden
> Subject: Re: AudioUnitSetParameter question
>
> John,
>
> You're not doing anything wrong. There is a bug particular to the reverb
> AudioUnit which makes it ignore parameter changes. You still can set
> a particular preset of the reverb with the kAudioUnitProperty_ReverbRoomType
> property using one of the enums from AudioUnitProperties.h
>
> enum {
> kReverbRoomType_SmallRoom = 0,
> kReverbRoomType_MediumRoom = 1,
> kReverbRoomType_LargeRoom = 2,
> kReverbRoomType_MediumHall = 3,
> kReverbRoomType_LargeHall = 4,
> kReverbRoomType_Plate = 8
> };
>
> Sorry about the trouble. We expect this will be fixed.
>
> Some other improvements to the reverb, perhaps improved quality, etc.
> may be coming as well...
>
> Chris Rogers
> CoreAudio
>
>
>> I'm trying to use AudioUnitSetParameter to set some of the options
>> on the built-in reverb audio unit, and I must be doing something
>> wrong because it doesn't seem to be working.
>>
>> First, I use AudioUnitGetProperty with
>> kAudioUnitProperty_ParameterList, and then AudioUnitGetProperty with
>> kAudioUnitProperty_ParameterInfo to get the list of parameters that
>> the reverb audio unit supports.
>>
>> So, as an example, "decay time" has a parameter ID of 0, min value
>> of .1, and max value of 5. I see by the flags that it is in the
>> global scope and both readable and writable.
>>
>> If I try to do the following, however, it doesn't seem to be working:
>> theStatus = AudioUnitSetParameter(reverbAU, 0,
>> kAudioUnitScope_Global, 0, [sender floatValue], 0);
>>
>> When I say "doesn't seem to be working," I mean that I can't hear
>> any difference between the max value, the min value, or anything in
>> between. (The same goes for all the other properties.) There are no
>> errors reported from the calls as far as I can tell.
>>
>> The things that I think might be wrong in that call are the
>> inElement value, and the inBufferOffsetInFrames (arguments 4 and 6).
>> Should they be something other than zero?
>>
>> If anyone has ideas on why this isn't working, I would appreciate
>> hearing about it.
>>
>> --john
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>
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