RPi Text to Speech (Speech Synthesis)

This guide shows you three easy methods of getting your Raspberry Pi to talk, and describes the pros and cons of each.

Why use Text to Speech?
It’s very easy add to your program - just output a string to the speech function instead of the screen. You don’t need an expensive/complicated LCD or monitor for your project - just use any old mp3 player loudspeaker or PC loudspeaker which you have probably got lying around - or even an earphone works well for debugging purposes too.

You could use speech output for: (i) status messages - e.g. internet connection made or IP address on a headless RPi; (ii) user interface - e.g. speak the mode selected or station name with button presses on an RPi internet radio; (iii) main functionality - e.g. tell the time and read the weather forecast on your RPi alarm clock.

Install supporting packages
Speech output requires a few audio software packages to be installed on your RPi. They may be already there but it does no harm to try to install these listed below anyway. The installer will let you know if the package is already present on your RPi. The instructions below are based on the Raspbian distribution (August 2012).

Firstly I recommend updating your Raspbian distribution if you have not recently already done so. Speech did not work for me until I did this. This may take 30 - 60 minutes depending on your connection speed etc. To do this:

sudo apt-get update sudo apt-get upgrade

If you do not already have sound on your RPi then you will need the alsa sound utilities: sudo apt-get install alsa-utils and edit the file /etc/modules using: sudo nano /etc/modules to have line: snd_bcm2835 If this line is already there then leave the file as is!

Install the mplayer audio/movie player with: sudo apt-get install mplayer To sort out the mplayer error message, edit file /etc/mplayer/mplayer.conf using: sudo nano /etc/mplayer/mplayer.conf to add line nolirc=yes

Cepstral Text to Speech
Cepstral is a commercial Text to Speech engine that is installed on the Pi and does not require an Internet connection. The voices are higher quality than open source solutions and pricing is dependent on the use case. More information is available is their website:

https://www.cepstral.com/raspberrypi

Festival Text to Speech
The first speech package I tried was Festival. It worked fine and produces a voice like a rough sounding robot. This may be just what you need if you are adding speech to your RPi robot project.

Install Festival with: sudo apt-get install festival

Try out Festival with: echo “Just what do you think you're doing, Dave?” | festival --tts or to speak RPi’s IP address: hostname -I | festival -tts

Espeak Text to Speech
Espeak is a more modern speech synthesis package than Festival. It sounds clearer but does wail a little. If you are making an alien or a RPi witch then it’s the one for you! Seriously it is a good allrounder with great customisation options.

Install Espeak with: sudo apt-get install espeak

Test Espeak with: English female voice, emphasis on capitals (-k), speaking slowly (-s) using direct text:- espeak -ven+f3 -k5 -s150 "I've just picked up a fault in the AE35 unit"

Google Text to Speech
Google’s Text to Speech engine is a little different to Festival and Espeak. Your text is sent to Google’s servers to generate the speech file which is then returned to your Pi and played using mplayer. This means you will need an internet connection for it to work, but the speech quality is superb.

I used used ax206geek’s bash script to access the Google Text to Speech engine:

Create a file speech.sh with: nano speech.sh

Add these lines to the file and save it (in nano editor use CTRL-O writeOut) say { local IFS=+;/usr/bin/mplayer -ao alsa -really-quiet -noconsolecontrols "http://translate.google.com/translate_tts?tl=en&q=$*"; } say $* Alternatively save from here:
 * 1) !/bin/bash

Add execute permissions to your script with: chmod u+x speech.sh

Test it using: ./speech.sh Look Dave, I can see you're really upset about this.

EXTRA: Dan Fountain improved on the above script to speak any length of text (Google limits you to 100 bytes normally). His excellent easy-to-read webpage describes this at http://danfountain.com/2013/03/raspberry-pi-text-to-speech/

Recommendations
I hope this guide has given you some ideas of how you can make use of speech output in your own project. As to which speech package to recommend, Festival works well enough, Espeak is clearer and so easier to understand and the Google engine gives super quality but is useless if you internet connection goes down. Maybe implement a speech function which first does a ping to Google before deciding whether to use Google or Espeak as its output engine?

All comments/suggestions welcome! Let me know for what you have used speech on your Pi - StevenP on the official Raspberry Pi Forum.