TtsEngineAction TtsEngineAction TtsEngineAction TtsEngineAction Enum


Specifies the Speech Synthesis Markup Language (SSML) action to be taken in rendering a given TextFragment.

public enum class TtsEngineAction
public enum TtsEngineAction
type TtsEngineAction = 
Public Enum TtsEngineAction


Bookmark Bookmark Bookmark Bookmark 3

Indicates that TextFragment is to be used as the contents of a bookmark.

ParseUnknownTag ParseUnknownTag ParseUnknownTag ParseUnknownTag 7

Indicates that no action has been determined from SSML input.

Pronounce Pronounce Pronounce Pronounce 2

Requests that input TextFragment text be interpreted as phonemes.

Silence Silence Silence Silence 1

Indicates that a TextFragment contains no text to be rendered as speech.

Speak Speak Speak Speak 0

Requests that the associated TextFragment should be processed and spoken.

SpellOut SpellOut SpellOut SpellOut 4

Indicates that text values provided by a TextFragment through its TextToSpeak property are to be synthesize as individual characters.

StartParagraph StartParagraph StartParagraph StartParagraph 6

Indicates state of paragraph.

StartSentence StartSentence StartSentence StartSentence 5

Indicates start of sentence.


The example below is part of a custom speech synthesis implementation inheriting from TtsEngineSsml, and using the use of TextFragment, FragmentState, and TtsEventId

The implementation of Speak

  1. Receives an array of TextFragment instances and creates a new array of TextFragment instances to be passed to the Speak method on an underlying synthesis engine.

  2. If the TtsEngineAction enumeration value by found from the Action property on the FragmentState returned by the State property of each TextFragment instance is Speak, the implementation

    • Translates Americanism to Britishisms in the text to be spoken.

    • If the EventInterest property on the EventInterest interfaces provided to the implementation support the TtsEventId event type, an event to drive a synthesizer progress meter is created.

  3. A speech rendering engine is then called with the modified TextFragment array.

private const int WordBoundaryFlag = 1 << (int)TtsEventId.WordBoundary;  
private readonly char[] spaces = new char[] { ' ', '\t', '\r', '\n' };  
internal struct UsVsUk  
  internal string UK;  
  internal string US;  

override public void Speak (TextFragment [] frags, IntPtr wfx, ITtsEngineSite site)  
  TextFragment [] newFrags=new TextFragment[frags.Length];  

  for (int i=0;i<frags.Length;i++){  
    newFrags[i].TextToSpeak = frags[i].TextToSpeak.Substring(frags[i].TextOffset,  
    newFrags[i].TextLength = newFrags[i].TextToSpeak.Length;  
    newFrags[i].TextOffset = 0;  
    if (newFrags[i].State.Action == TtsEngineAction.Speak) {  
      //Us to UK conversion  
      foreach (UsVsUk term in TransList) {  
      newFrags[i].TextToSpeak.Replace(term.US, term.UK);  
      //Generate progress meter events if supported  
      if ((site.EventInterest & WordBoundaryFlag) != 0) {  
      string[] subs = newFrags[i].TextToSpeak.Split(spaces);  

      foreach (string s in subs) {  
        int offset = newFrags[i].TextOffset;  
        SpeechEventInfo spEvent = new SpeechEventInfo((Int16)TtsEventId.WordBoundary,   
                 s.Length, new IntPtr(offset));  
        offset += s.Length;  
        if (s.Trim().Length > 0) {  
          SpeechEventInfo[] events = new SpeechEventInfo[1];  
          events[0] = spEvent;  
          site.AddEvents(events, 1);  

  _baseSynthesize.Speak(newFrags, wfx, site);  



TtsEngineAction represents requests for servicing a TextFragment. The actions correspond closely to elements in the SSML specification and are implemented on the text returned by the TextToSpeak property on a TextFragment.

The TtsEngineAction value associated with a TextFragment is returned by the State property.

Processing of the TtsEngineAction value returned by the State property is handled by a speech synthesizes implementation of the Speak method on a class derived from TtsEngineSsml.

Applies to