Re: AudioUnitScheduleParameters with an AUTimePitch unit.
Re: AudioUnitScheduleParameters with an AUTimePitch unit.
- Subject: Re: AudioUnitScheduleParameters with an AUTimePitch unit.
- From: William Stewart <email@hidden>
- Date: Fri, 10 Oct 2008 12:57:03 -0700
A parameter that can be ramped will be marked in a particular way:
kAudioUnitParameterFlag_CanRamp
will be set in a parameter's info struct.
You can see the settings for an AU by running auval on it:
>>>
# # # 24 Global Scope Parameters:
Parameter ID:0
Name: rate
Parameter Type: Rate
Values: Minimum = 0.250000, Default = 1.000000, Maximum = 4.000000
Flags: Display Logarithmic, High Resolution, Readable, Writable
-parameter PASS
>>>
So, from this you can see that the time pitch's rate parameter is not
ramp-able (arguably we should be returning an error here)
You can achieve the ramp by just using set parameter over a few buffer
calls (the parameter itself will be de-zippered).
Bill
On Oct 10, 2008, at 7:23 AM, John Clayton wrote:
Hi All,
I'd like to ramp the playback rate of an AUTimePitch unit, I've read
the docs and searched the examples + google, but still my rate
change on the pitch unit doesn't seem to take effect when I call
AudioUnitScheduleParameters.
I'm registering for render-notify like this:
if(mPitchCallback || mPitchCallbackRefCon)
XThrowIfError(AudioUnitAddRenderNotify(mPitchUnit,
mPitchCallback,
mPitchCallbackRefCon), "setting output render callback");
and in this callback, I have code like this:
- (double) rateValueForPercent:(double)pcnt {
double rateValue = fabs(0.5 - pcnt);
if(rateValue < 0.25)
rateValue = 0.25;
if(rateValue > 1.0)
rateValue = 1.0;
return rateValue;
}
notes: pcnt is the total percentage complete (always from 0 thru 1.0)
if(*ioActionFlags & kAudioUnitRenderAction_PreRender) {
// set the rate to fabs(0.5 - pcnt)
AudioUnit pitchUnit = [self pitchUnit];
AudioUnitParameterEvent inEvent;
memset(&inEvent, 0, sizeof(inEvent));
inEvent.scope = kAudioUnitScope_Output;
inEvent.element = 0;
inEvent.parameter = kTimePitchParam_Rate;
inEvent.eventType = kParameterEvent_Ramped;
// for this set of frames, what are the ramping values associated
with the begin/end times?
double beginRateValue = [self rateValueForPercent:pcnt];
double endRateValue = [self rateValueForPercent:endPcnt];
inEvent.eventValues.ramp.startValue = beginRateValue;
inEvent.eventValues.ramp.endValue = endRateValue;
inEvent.eventValues.ramp.durationInFrames = inNumberFrames;
inEvent.eventValues.ramp.startBufferOffset = 0;
ComponentResult res = AudioUnitScheduleParameters(pitchUnit,
&inEvent, 1);
if(res != 0)
printf("cant set up the scheduled param: %d\r\n", res);
}
}
No errors are printed to the console.
I hear audio being played back, but the pitch never changes - is the
error obvious perhaps? Keen for any feedback / help, thanks.
Thanks--
John Clayton
Skype: johncclayton
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