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Design the Parameter Interface

In this section you work out the parameter portion of the programmatic interface between your audio unit and its view. End users will vary these parameters to control your audio unit in real time.

First, specify which sound attributes you’d like the user to be able to control. For this project, use the following:

• Tremolo frequency—the number of tremolo cycles per second.

• Tremolo depth—the mix between the input signal and the signal with tremolo applied. At a depth of 0%, there is no tremolo effect. At a depth of 100%, the effect ranges from full amplitude to silence.

• Tremolo waveform—the shape of the tremolo effect, such as sine wave or square wave.

Second, specify for each parameter:

• User interface name as it appears in the audio unit view

• Programmatic name, also called the parameter ID, used in the GetParameterInfo method in the audio unit implementation file

• Unit of measurement, such as gain, decibels, or hertz

• Minimum value

• Maximum value

• Default value

The following tables specify the parameter design. You'll use most of these values directly in your code. Specifying a "Description" is for your benefit while developing and extending the audio unit. You can reuse the description later in online help or a user guide.

It's easy to add, delete, and refine parameters later. For example, if you were creating an audio level adjustment parameter, you might start with a linear scale and later change to a logarithmic scale. For the tremolo unit you're building, you might later decide to add additional tremolo waveforms.

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