System information

Alternatively, if you’re having issues with the Festival server, you could use the follow-
ing method to generate files with the text2wave application supplied with the festival
package:
exten => 202,1,Verbose(2,Trying out Festival)
same => n,Answer()
; *** This line should not have any line breaks
same => n,System(echo "This is a test of Festival"
| /usr/bin/text2wave -scale 1.5 -F 8000 -o /tmp/festival.wav)
same => n,Playback(/tmp/festival)
same => n,System(rm -f /tmp/festival.wav)
same => n,Hangup()
You should now have enough to get started with generating text-to-speech audio for
your Asterisk system. The audio quality is not brilliant, and the speech generated is not
clear enough to be easy to understand over a telephone, but for development and testing
purposes Festival is an application that can fill the gap until you’re ready for a more
professional-sounding text-to-speech generator such as Cepstral.
Cepstral
Cepstral is a text-to-speech engine that works in a similar manner as the Festival()
application in the dialplan, but produces much higher-quality sound. Not only is the
quality significantly better, but Cepstral has developed a text-to-speech engine that
emulates Allison’s voice, so your text-to-speech engine can sound the same as the Eng-
lish sound files that ship with Asterisk by default, to give a consistent experience to the
caller.
Cepstral is commercial module, but for around $30 you can have a text-to-speech en-
gine that is clearer, is more consistent with other sound prompts on your system, and
provides a more pleasurable experience for your callers. The Cepstral software and
installation instructions can be downloaded from the Digium.com webstore at http://
www.digium.com/en/products/software/cepstral.php.
Conclusion
In this chapter we focused on integrating Asterisk with external services that may not
be directly related to generating or handling calls, but do enable tighter coupling with
existing services on your network by providing information for call routing, or infor-
mation about your users from your existing infrastructure.
442 | Chapter 18: External Services