TextFragment.TextToSpeak Property

Sets or gets the speech text of the fragment.

Namespace:  System.Speech.Synthesis.TtsEngine
Assembly:  System.Speech (in System.Speech.dll)

public string TextToSpeak { get; set; }

Property Value

Type: System.String
A System.String is returned or can be used to set the speech text to be used by a speech synthesis engine to generate audio output.

The default value of this property is System.String.Empty.

Applications are free to completely change the value of TextToSpeak.

Resetting the value of TextToSpeak will not change the value of TextOffset and TextLength.

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

    Particular care is used to respect the TextOffset, TextLength on the original TextFragment when creating the TextToSpeak on the new TextFragment instances.

  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 ITtsEngineSite interfaces provided to the implementation support the WordBoundary event type, a SpeechEventInfo instance is used to create 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].State=frags[i].State;
    //truncate
    newFrags[i].TextToSpeak = frags[i].TextToSpeak.Substring(frags[i].TextOffset,
                               frags[i].TextLength);
    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, 
                (Int16)EventParameterType.Undefined, 
                 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);
  
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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