Inside Macintosh: Sound /

Chapter 5 - Sound Components / Sound Components Reference

Sound Component-Defined Routines / Managing Sound Components

SoundComponentGetSourceData

A utility component must implement the SoundComponentGetSourceData function. A sound output device component calls this function on its source component when it needs more data.

pascal ComponentResult SoundComponentGetSourceData 
                           (ComponentInstance ti, 
                              SoundComponentDataPtr *sourceData);

ti

A component instance that identifies your sound component.

sourceData

On output, a pointer to a sound component data record that specifies the type and location of the data your component has processed.

DESCRIPTION

Your SoundComponentGetSourceData function is called when the sound component immediately following your sound component in the sound component chain needs more data. Your function should generate a new block of audio data, fill out a sound component data record describing the format and location of that data, and then return the address of that record in the sourceData parameter.

Your SoundComponentGetSourceData function might itself need to get more data from its source component. To do this, call through to the source component's SoundComponentGetSourceData function. If your component cannot generate any more data, it should set the sampleCount field of the sound component data record to 0 and return noErr.

IMPORTANT

Sound output device components do not need to implement this function, but all utility components must implement it.

RESULT CODES

Your SoundComponentGetSourceData function should return noErr if successful or an appropriate result code otherwise.