Inside Macintosh: Sound /

Chapter 3 - Sound Input Manager / Sound Input Manager Reference

Sound Input Manager Routines / Converting Between Milliseconds and Bytes

SPBMilliSecondsToBytes

You can use the SPBMilliSecondsToBytes function to determine how many bytes a recording of a certain duration will use.

FUNCTION SPBMilliSecondsToBytes (inRefNum: LongInt; 
                              VAR milliseconds: LongInt): OSErr;

inRefNum

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

milliseconds

On entry, the duration of the recording in milliseconds. On exit, the number of bytes that sampled-sound data would occupy for a recording of the specified duration on the device specified by the inRefNum parameter.

DESCRIPTION

The SPBMilliSecondsToBytes function reports how many bytes are required to store a recording of duration milliseconds, given the input device's current sample rate, sample size, number of channels, and compression factor.

SPECIAL CONSIDERATIONS

You can call the SPBMilliSecondsToBytes function at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SPBMilliSecondsToBytes function are

Trap macro	Selector
_SoundDispatch	$04400014

RESULT CODES

noErr	0	No error
siBadSoundInDevice	-221	Invalid sound input device