Re: Indexed Audio Unit Parameter
Re: Indexed Audio Unit Parameter
- Subject: Re: Indexed Audio Unit Parameter
- From: Chris Johnson <email@hidden>
- Date: Sun, 13 Apr 2008 12:04:49 -0400
On Apr 13, 2008, at 2:42 AM, Chad Wagner wrote:
I'm having a problem with audio unit parameters whose "unit" is set
to kAudioUnitParameterUnit_Indexed. Everything works when the
indexed values start at 0 and I provide an array of value strings.
But one of my indexed parameters has no value strings, which causes
a bus error in auval, and another indexed parameter starts at 1
rather than 0, but auval seems to be looking for an extra value
string as if they started at 0 (i.e. my range is 1 to 3, I provide
an array with 3 strings, but auval is looking for a 4th). In all
cases, changing the unit to generic makes the problem go away, as
does leaving it as indexed but starting at 0 and providing an array
of value strings...
e.g. one of the parameters is a MIDI channel, which should be an
integer from 1 to 16. I don't want it to start at 0, and it seems
absurd to have to specify an array of strings "1" to "16". Is
there a better way?
I have a similar Indexed parameter in Classic Channel and I've just
looked up what it was doing- turns out my range is 1 to 3 and I'm
supplying static const int variables for the values, and static
CFStringRef for the names in the popup... and in
GetParameterValueStrings, it's making the array of value strings you
mention. Then in GetParameterInfo I am supplying the const variables
to mark what number means what selection, and my minValue is the
const equal to one (as is kDefaultValue_ParamOne)...
This is puzzling me- I'm trying to figure out if I took the string
labels out, would it break. It certainly appears that apart from the
labels, I'm setting the range as 1 to 3 with default value as one and
auval does not complain... perhaps it's odd, but if supplying an
array of strings "1" to "16" makes the parameter handling more
bulletproof, why not? It's useful to know that if you try to use
indexed parameters (with no associated string array) that aren't from
zero, there's a problem- thanks.
Chris Johnson
airwindows
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