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using AudioUnitScheduleParameters
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using AudioUnitScheduleParameters


  • Subject: using AudioUnitScheduleParameters
  • From: steph ohara <email@hidden>
  • Date: Mon, 28 Jan 2013 21:25:01 -0800 (PST)


I've been playing around with AU3DMixerEmbedded audio unit and play rates and hoping someone has some experience using this audio unit.

I am wanting to change the playrate during a render cycle. The playrate changes but setting an offest which i've calculated doesn't work.

Before moving on, I wanted to confirm some questions.
 
In the headers, for AudioUnitSetParameter(), it states
 inBufferOffsetInFrames - generally should be set to zero - see AudioUnitScheduleParameters
Does this mean setting it to something other than zero will work? 
Setting it to a non-zero value doesn't do anything.

I've tried using AudioUnitScheduleParameters() :

     AudioUnitParameterEvent event;
    event.parameter = k3DMixerParam_PlaybackRate;
    event.scope = kAudioUnitScope_Input;
    event.element = 0;
    event.eventType = kParameterEvent_Immediate;
    event.eventValues.immediate.bufferOffset = offset;
    event.eventValues.immediate.value = pitch;

    OSStatus err = noErr;
    err = AudioUnitScheduleParameters(track->auUnit,&event,1);
....

The rate changes but offset value doesn't seem to work. I checked if the audio unit could ramp so i could use (kParameterEvent_Ramped) but it seems this audio unit doesn't ramp. but does this mean it still can schedule using kParameterEvent_Immediate?

Should these calls be made ONLY in a Render Notifier with pre flag set? 

I am planning to write a bunch of code to test this all out but would love not to :)

cheers steph


soh_la : music software development
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