In Windows Phone 8.1 you can generate a
SpeechSynthesisStream using text to speech. We earlier tipped you on
Using text to speech in Windows Phone 8 and 8.1
You can use the output
SpeechSynthesisStream and save it as a
.wav audio file in app’s local storage.
This is not the best method to save the speech stream to audio as it takes a long time to get processed.
Sound off in comments/forums if you find a workaround.
UPDATE: We just found another method to do it and it seems to be quite faster. The sample Transcoding media project uses
Windows.Media.Transcoding API to transcode a media file in a Windows Store app.