Converting Between Milliseconds and Bytes3

The Sound Input Manager provides two routines that allow you to convert between millisecond and byte recording values.

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

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