Inside Macintosh: Sound /

Chapter 3 - Sound Input Manager / Sound Input Manager Reference

Sound Input Manager Routines / Opening and Closing Sound Input Devices

SPBOpenDevice

You can use the SPBOpenDevice function to open a sound input device.

FUNCTION SPBOpenDevice (deviceName: Str255; permission: Integer; 
                        VAR inRefNum: LongInt): OSErr;

deviceName

The name of the sound input device to open, or the empty string if the default sound input device is to be opened.

permission

A flag that indicates whether subsequent operations with that device are to be read/write or read-only.

inRefNum

On exit, if the function is successful, a device reference number for the open sound input device.

DESCRIPTION

The SPBOpenDevice function attempts to open a sound input device having the name indicated by the deviceName parameter. If SPBOpenDevice succeeds, it returns a device reference number in the inRefNum parameter. The permission parameter indicates whether subsequent operations with that device are to be read/write or read-only. If the device is not already in use, read/write permission is granted; otherwise, only read-only operations are allowed. To make any recording requests or to call the SPBSetDeviceInfo function, read/write permission must be available. Use these constants to request the appropriate permission:

CONST
   siReadPermission     = 0;     {open device for reading}
   siWritePermission    = 1;     {open device for reading/writing}

You can request that the current default sound input device be opened by passing either a zero-length string or a NIL string as the deviceName parameter. If only one sound input device is installed, that device is used. Generally you should open the default device unless you specifically want to use some other device. You can get a list of the available devices by calling the SPBGetIndexedDevice function.

SPECIAL CONSIDERATIONS

Because the SPBOpenDevice function allocates memory, you should not call it at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SPBOpenDevice function are

Trap macro	Selector
_SoundDispatch	$05180014

RESULT CODES

noErr	0	No error
permErr	-54	Device already open for writing
siBadDeviceName	-228	Invalid device name