Sound Output Latency API

The following selector for the SoundComponentGetInfo function is used by QuickTime to retrieve the sound latency:

siOutputLatency (SoundComponentGetInfo)

Retrieves the audio latency from the specified sound output component.



 
#define siOutputLatency `olte'

siOutputLatency: Gets the audio latency from the Sound Output Component. The infoPtr parameter points to a time record.

DISCUSSION

The following code snippet shows an example implementation of this selector:



 
static pascal ComponentResult mySoundGetInfo(SoundComponentGlobalsPtr globals, SoundSource 

                     sourceID, OSType selector, void *infoPtr)



 
{

    ComponentResult             result = noErr;

    PrefStructPtr               prefsPtr;



    prefsPtr = *(globals->prefsHandle);



    switch (selector) {



case siSampleSize:              // return current sample size

            *((short *) infoPtr) = (short)prefsPtr->sampleSize;

            break;



case siOutputLatency:                                               // return the sound output 

latency

        // in this example, 25 ms

if (infoPtr != nil) {

                infoPtr->value.hi = 0;

                infoPtr->value.lo = 25;             // sound latency

                infoPtr->scale = 1000;              // 1 ms scale

                infoPtr->base = nil;

            }

            break;



. . .



}