Re: AudioUnitParameterUnit requests
Re: AudioUnitParameterUnit requests
- Subject: Re: AudioUnitParameterUnit requests
- From: Bill Stewart <email@hidden>
- Date: Fri, 18 Oct 2002 14:15:21 -0700
Just getting this clear in my own mind:)
I would imagine that if an AU publishes this parameter unit, AND the AU has
the ability to follow tempo changes from the host, then the AU would also
publish a boolean property (in our example)
Filter LFO Tempo (== 60->180)
Fliter LFO Beats (==0->4?)
Filter LFO Independent Tempo (T/F)
(or Filter LFO Track Host Temp (T/F))
(either way is fine)
Then, if the user wants the unit to track host tempo and it can, then the
"Filter LFO Tempo" above would become a read only parameter?
(And this would need to be somewhat dynamic in the AU as:
(1) Some hosts may not support tempo
(2) Some usage scenarios might not have a tempo
So - typically, we'd expect the HostCallback property that sets this
callback for tempo, to be done before the AU's UI (or hopefully before the
AU is initialized - though that can't always be guaranteed) is shown - so
the AU couldn't code this parameter directly (as it can with most other
parameters), but would have to determine the action of the parameter
dynamically...
(And also - setting a tempo parameter if the "track host tempo" parameter is
set, would then fail)
The reason I'd like to get clear on this, is that we're trying to spec out a
validation tool for audio units to ensure some consistency of behaviour - so
I think I'd like to understand how users/AU writers expect this to behave)
Thanks
Bill
on 18/10/02 1:56 PM, Marc Poirier wrote:
>
> Here is the definition of these parameter unit type constants:
>
> kAudioUnitParameterUnit_Octaves = 21,
>
> /* octaves in relative pitch where a value of 1 is equal to 1200 cents*/
>
> kAudioUnitParameterUnit_BPM = 22,
>
> /* beats per minute, ie tempo */
>
> kAudioUnitParameterUnit_Beats = 23,
>
> /* time relative to tempo, ie. 1.0 at 120 BPM would equal 1/2 a second */
>
> kAudioUnitParameterUnit_Milliseconds = 24
>
> /* parameter is expressed in milliseconds */
>
>
Sweet, thanks.
>
>
_Beats is actually the unit type that I forgot to suggest (as I go about
>
porting my VST plugs, I come accross more parameter types), thanks for
>
reading my mind and adding that, too. :)
>
>
> The only area to clear up is what kind of parameter range do you expect an
>
> octave param to express - we're presuming that this parameter indicates a
>
> *relative* value - where 1 would change the parameter value UP an octave,
>
> and -1 would change the parameter value DOWN an octave... Fractional values?
>
> (If so 0.5 would be half an octave - ie. Equivalent to 600 cents)?
>
>
I definitely had relative and fractional in mind when I made the
>
suggestion.
>
>
>
Marc
>
>
P.S.- In case I haven't mentioned it before, I really appreciate how you
>
CoreAudio folks post API changes to the list so that we can integrate them
>
into our base source files immediately and don't need to wait for public
>
SDK revision releases.
>
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