I'm new to this Forum as well as using Raspberry Pi 2 for the first time. I'm currently making a learning device for a blind person. My project requires text-to-speech and speech-to-text conversion to work properly to deliver the pronunciation of words and for the input from the blind user. I'm done with the text-to-speech part and am presently working on the speech-to-text. I'm looking for an Off-line speech synthesizer. Please can you suggest some Software/APIs which I can use for this conversion?
I think the "nano" project - or parts thereof - (that soundly beat me in the Christmas Prizes for Best project of 2015) - might be of interest. It does feature both text-to-speech and speech-to-text if I recall correctly - and Patrick Cook is a currently active member here.
Once your reputation gets to 20 (I think) you might catch him in The Bakery (the Main RPi Chat Room) occasionally which means you can find out how he is progressing with it straight from the horse's mouth...