Inside Macintosh: Sound /

Chapter 3 - Sound Input Manager / Sound Input Manager Reference

Sound Input Manager Routines / Converting Between Milliseconds and Bytes

SPBBytesToMilliSeconds

You can use the SPBBytesToMilliSeconds function to determine the maximum duration of a recording that can fit in a buffer of a certain size.

FUNCTION SPBBytesToMilliSeconds (inRefNum: LongInt; 
                                 VAR byteCount: LongInt): OSErr;

inRefNum

The device reference number of the sound input device, as obtained from the SPBOpenDevice function.

byteCount

On entry, a value in bytes. On exit, the number of milliseconds of recording on the device specified by the inRefNum parameter that would be necessary to fill a buffer of such a size.

DESCRIPTION

The SPBBytesToMilliSeconds function reports how many milliseconds of audio data can be recorded in a buffer that is byteCount bytes long, given the input device's current sample rate, sample size, number of channels, and compression factor.

SPECIAL CONSIDERATIONS

You can call the SPBBytesToMilliSeconds function at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SPBBytesToMilliSeconds function are

Trap macro	Selector
_SoundDispatch	$04440014

RESULT CODES

noErr	0	No error
siBadSoundInDevice	-221	Invalid sound input device