Inside Macintosh: Sound /

Chapter 1 - Introduction to Sound on the Macintosh / Sound Reference

Routines / Recording Sounds

SndRecord

You can use the SndRecord function to record sound resources into memory.

FUNCTION SndRecord (filterProc: ProcPtr; corner: Point; 
                     quality: OSType; VAR sndHandle: Handle): 
                     OSErr;

filterProc

A pointer to an event filter function that determines how user actions in the sound recording dialog box are filtered (similar to the filterProc parameter specified in a call to the ModalDialog procedure). By specifying your own filter function, you can override or add to the default actions of the items in the dialog box. If filterProc isn't NIL, SndRecord filters events by calling the function that filterProc points to.

corner

The horizontal and vertical coordinates of the upper-left corner of the sound recording dialog box (in global coordinates).

quality

The desired quality of the recorded sound.

sndHandle

On entry, a handle to some storage space or NIL. On exit, a handle to a valid sound resource (or unchanged, if the call did not execute successfully).

DESCRIPTION

The SndRecord function records sound into memory. The recorded data has the structure of a format 1 'snd ' resource and can later be played using the SndPlay function or can be stored as a resource. SndRecord displays a sound recording dialog box and is always called synchronously. Controls in the dialog box allow the user to start, stop, pause, and resume sound recording, as well as to play back the recorded sound. The dialog box also lists the remaining recording time and the current microphone sound level.

The quality parameter defines the desired quality of the recorded sound. Currently, three values are recognized for the quality parameter:

CONST
   siBestQuality        = 'best';   {the best quality available}
   siBetterQuality      = 'betr';   {a quality better than good}
   siGoodQuality        = 'good';   {a good quality}

The precise meanings of these parameters are defined by the sound input device driver. For Apple-supplied drivers, this parameter determines whether the recorded sound is to be compressed, and if so, whether at a 6:1 or a 3:1 ratio. The quality siBestQuality does not compress the sound and provides the best quality output, but at the expense of increased memory use. The quality siBetterQuality is suitable for most nonvoice recording, and siGoodQuality is suitable for voice recording.

The sndHandle parameter is a handle to some storage space. If the handle is NIL, the Sound Input Manager allocates a handle of the largest amount of space that it can find in your application's heap and returns this handle in the sndHandle parameter. The Sound Input Manager resizes the handle when the user clicks the Save button in the sound recording dialog box. If the sndHandle parameter passed to SndRecord is not NIL, the Sound Input Manager simply stores the recorded data in the location specified by that handle.

SPECIAL CONSIDERATIONS

Because the SndRecord function moves memory, you should not call it at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SndRecord function are

Trap macro	Selector
_SoundDispatch	$08040014

RESULT CODES

noErr	0	No error
userCanceledErr	-128	User canceled the operation
siBadSoundInDevice	-221	Invalid sound input device
siUnknownQuality	-232	Unknown quality

SEE ALSO

For an example of how to record a sound resource using the SndRecord function, see "Recording a Sound Resource" on page 1-28. See the chapter "Dialog Manager" in Inside Macintosh: Macintosh Toolbox Essentials for a complete description of event filter functions.