Inside Macintosh: Sound /

Chapter 4 - Speech Manager / Speech Manager Reference

Speech Manager Routines / Starting, Stopping, and Pausing Speech

SpeakText

You can use the SpeakText function to have the Speech Manager speak a buffer of text.

FUNCTION SpeakText (chan: SpeechChannel; textBuf: Ptr; 
                     textBytes: LongInt): OSErr;

chan

The speech channel through which speech is to be spoken.

textBuf

A pointer to the first byte of text to spoken.

textBytes

The number of bytes of text to spoken.

DESCRIPTION

The SpeakText function converts the text stream specified by the textBuf and textBytes parameters into speech using the voice and control settings for the speech channel chan, which should be created with the NewSpeechChannel function. The speech is generated asynchronously. This means that control is returned to your application before the speech has finished (and probably even before it has begun). The maximum length of the text buffer that can be spoken is limited only by the available RAM.

If SpeakText is called while the channel is currently busy speaking the contents of a prior text buffer, it immediately stops speaking from the prior buffer and begins speaking from the new text buffer as soon as possible. If you pass a zero-length string (or, in C, a null pointer) to SpeakText, the Speech Manager stops all speech currently being synthesized by the speech channel specified in the chan parameter without generating additional speech.

WARNING

The text buffer must be locked in memory and must not move while the Speech Manager processes it. This buffer is read at interrupt time, and moving it could cause a system crash. If your application defines a text-done callback procedure, then it can move the text buffer or dispose of it once the callback procedure is executed.

SPECIAL CONSIDERATIONS

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

ASSEMBLY-LANGUAGE INFORMATION

The trap macro and routine selector for the SpeakText function are

Trap macro	Selector
_SoundDispatch	$0624000C

RESULT CODES

noErr	0	No error
invalidComponentID	-3000	Speech channel is uninitialized or bad