Inside Macintosh: Sound /

Chapter 4 - Speech Manager / Speech Manager Reference

Data Structures

Speech Version Information Records

By calling the GetSpeechInfo function with the soSynthType selector, you can obtain a speech version information record, which provides information about the speech synthesizer currently being used. The SpeechVersionInfo data type defines a speech version information record.

TYPE SpeechVersionInfo =
RECORD
   synthType:           OSType;        {general synthesizer type}
   synthSubType:        OSType;        {specific synthesizer type}
   synthManufacturer:   OSType;        {synthesizer creator ID}
   synthFlags:          LongInt;       {synthesizer feature flags}
   synthVersion:        NumVersion;    {synthesizer version number}
END;

Field Description

synthType

The general type of the synthesizer. For the current version of the Speech Manager, this field always contains the value kTextToSpeechSynthType, indicating that the synthesizer converts text into speech.

synthSubType

The specific type of the synthesizer. Currently, no specific types of synthesizer are defined. If you define a new type of synthesizer, you should register the four-character code for your type with Developer Technical Support.

synthManufacturer

A unique identification of a synthesizer engine. If you develop synthesizers, then you should register a different four-character code for each synthesizer you develop with Developer Technical Support. The creatorID field of the voice specification record and the synthCreator field of a speech extension data record should each be set to the value stored in this field for the desired synthesizer.

synthFlags

A set of flags indicating which synthesizer features are activated. The following constants define the bits in this field whose meanings are defined for all synthesizers:

               CONST
                  kNoEndingProsody     = 1;
                  kNoSpeechInterrupt   = 2;
                  kPreflightThenPause  = 4;

The kNoEndingProsody flag bit is used to control whether or not the speech synthesizer automatically applies ending prosody, the speech tone and cadence that normally occur at the end of a statement. Under normal circumstances (for example, when the flag bit is not set), ending prosody is applied to the speech when the end of the textBuf data is reached. This default behavior can be disabled by setting the kNoEndingProsody flag bit.

Some synthesizers do not speak until the kNoEndingProsody flag bit is reset, or they encounter a period in the text, or textBuf is full.

The kNoSpeechInterrupt flag bit is used to control the behavior of SpeakBuffer when called on a speech channel that is still busy. When the flag bit is not set, SpeakBuffer behaves similarly to SpeakString and SpeakText. Any speech currently being produced on the specified speech channel is immediately interrupted, and then the new text buffer is spoken. When the kNoSpeechInterrupt flag bit is set, however, a request to speak on a channel that is still busy processing a prior text buffer will result in an error. The new buffer is ignored and the error synthNotReady is returned. If the prior text buffer has been fully processed, the new buffer is spoken normally. One way of achieving continuous speech without using callback procedures is to continually call SpeakBuffer with the kNoSpeechInterrupt flag bit set until the function returns noErr. The function will then execute as soon as the first text buffer has been processed.

The kPreflightThenPause flag bit is used to minimize the latency experienced when the speech synthesizer is attempting to speak. Ordinarily, whenever a call to SpeakString, SpeakText, or SpeakBuffer is made, the speech synthesizer must perform a certain amount of initial processing before speech output is heard. This startup latency can vary from a few milliseconds to several seconds depending upon which speech synthesizer is being used. Recognizing that larger startup delays might be detrimental to certain applications, a mechanism is provided to allow the synthesizer to perform any necessary computations at noncritical times. Once the computations have been completed, the speech is able to start instantly. When the kPreflightThenPause flag bit is set, the speech synthesizer will process the input text as necessary to the point where it is ready to begin producing speech output. At this point, the synthesizer will enter a paused state and return to the caller. When the application is ready to produce speech, it should call the ContinueSpeech function to begin speaking.

synthVersion

The version number of the synthesizer.