How to convert Text to Wave using multi-threaded SAPI?

Question

I am trying to convert text to a wave file using the following function. It works great if called from the main user interface thread. But it does not work when called from another thread. What to call it from a multithreaded function?

void Pan_Channel::TextToPlaybackFile( CString Text, CString FileName )
{
 // Result variable
 HRESULT Result = S_OK;

 // Voice Object
 CComPtr<ISpVoice> cpVoice;

 // Create a SAPI Voice
 Result = cpVoice.CoCreateInstance( CLSID_SpVoice );

 // Audio format
 CSpStreamFormat cAudioFmt;

 // Set the audio format
 if( SUCCEEDED( Result ) )
 {
  Result = cAudioFmt.AssignFormat( SPSF_8kHz16BitMono );
 }

 // File Stream
 CComPtr<ISpStream> cpStream;

 // Call SPBindToFile, a SAPI helper method,  to bind the audio stream to the file
 if( SUCCEEDED( Result ) )
 {
  Result = SPBindToFile( FileName, SPFM_CREATE_ALWAYS, &cpStream,
   &cAudioFmt.FormatId(), cAudioFmt.WaveFormatExPtr() );
 }

 // set the output to cpStream so that the output audio data will be stored in cpStream
 if( SUCCEEDED( Result ) )
 {
  Result = cpVoice->SetOutput( cpStream, TRUE );
 }

  // Speak the text syncronously
 if( SUCCEEDED( Result ) )
 {
  Result = cpVoice->Speak( Text.AllocSysString(), SPF_DEFAULT, NULL );
 }

 // close the stream
 if( SUCCEEDED( Result ) )
 {
  Result = cpStream->Close();
 }

 // Release stream
 cpStream.Release();

 // Release voice object
 cpVoice.Release();
}

Answer 1

Have you combined another topic? COM must be initialized for each thread using it. Also .. are you using a COM object created in one thread in another thread? Since you need to set up a marker between threads if you do this ...