Re: AudioUnitParameterUnit requests
Re: AudioUnitParameterUnit requests
- Subject: Re: AudioUnitParameterUnit requests
- From: Bill Stewart <email@hidden>
- Date: Fri, 18 Oct 2002 12:47:01 -0700
OK
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 */
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)?
We thought we'd add one while we were at this...
A parameter unit type of the _BPM means that the delay will be timed off 120
beats per minute. If the audio unit is able to get Tempo/beat information
from the host, then the AU could decide to maintain the BPM value from the
host, or allow a separate BPM to be set by the user.
So far so good, but we still haven't told the AU what to do.
Thus we have another parameter unit called kAudioUnitParameterUnit_Beats
This then describes how that parameter will relate its timing to the tempo.
Here, we're expecting that a value of "1" means that the parameter is timed
to a beat (as expressed by _BPM - whether this is maintained by the host
tempo or set by the user), a value of "2" means the parameter is timed at 2
beats, a value of "0.5" means its timed at a half a beat, etc...
(Though this is not necessary, you can think of this in conventional music
notation where a beat is a quarter note, so a 0.5 is an eighth note, 2 is a
half note, etc) - however by using a floating point value here, so nicely
weird timings are possible:)
Typically an AU would publish these beat parameters in pairs... Ie...
Filter LFO Tempo (== 60->180)
Fliter LFO Beats (==0->4?)
Bill
on 18/10/02 11:07 AM, Art Gillespie wrote:
>
FWIW, I second all of those.
>
>
Best,
>
>
Art
>
>> 0xBA
>
>
On Friday, October 18, 2002, at 01:15 PM, Marc Poirier wrote:
>
>
> I think that I may have already requested one or two of these, but
>
> here's
>
> my current complete request list:
>
>
>
> kAudioUnitParameterUnit_Octaves
>
> kAudioUnitParameterUnit_BPM
>
> kAudioUnitParameterUnit_Milliseconds
>
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