10.1. Festival
Festival is a popular open source text-to-speech
engine. The basic premise of using Festival with Asterisk is that
your dialplan can pass a body of text to Festival, which will then
"speak" the text to the caller. Probably the most obvious use for
Festival would be to have it read your email to you when you are on
the road.
10.1.1. Getting Festival Set Up and
Ready for Asterisk
There are currently two ways to use Festival
with Asterisk. The first (and easiest) methodwithout having to
patch and recompile Festivalis to add the following text to
Festival's configuration file (festival.scm, usually located in /etc/ or /usr/share/festival/):
(define (tts_textasterisk string mode)
"(tts_textasterisk STRING MODE)
Apply tts to STRING. This function is specifically designed for use in
server mode so a single function call may synthesize the string. This
function name may be added to the server safe functions."
(let ((wholeutt (utt.synth (eval (list 'Utterance 'Text string)))))
(utt.wave.resample wholeutt 8000)
(utt.wave.rescale wholeutt 5)
(utt.send.wave.client wholeutt)))
You may place this text anywhere in the file, as
long as it is not between any other parentheses.
The second (and more traditional) way is to
compile Festival with an Asterisk-specific patch (located in the
contrib/ directory of the Asterisk
source).
Information on both of these methods is
contained in the README.festival
file, located in the contrib/
directory of the Asterisk source.
For either method, you'll need to modify the
Festival access list in the festival.scm file. Simply search for the word
"localhost," and replace it with the fully qualified domain name of
your server.
Both of these methods set up Festival to be able
to correctly communicate with Asterisk. After setting up Festival,
you should start the Festival server. You can then call the
Festival( ) application from within your dialplan.
10.1.2. Configuring Asterisk for
Festival
The Asterisk configuration file that deals with
Festival is aptly called festival.conf. Inside this file, you specify
the hostname and port of your Festival server, as well some
settings for the caching of Festival speech. For most installations
(if you're going to run Festival on your Asterisk server), the
defaults will work just fine.
10.1.3. Starting the Festival
Server
To start the Festival server for debugging
purposes, simply run festival with the server
argument, like this:
[root@asterisk ~]# festival --server
Once you're sure that the Festival server is
running and not rejecting your connections, you can start Festival
by typing:
[root@asterisk ~]# festival_server 2>&1 >/dev/null &
10.1.4. Calling Festival from the
Dialplan
Now that Festival is configured and the Festival
server is started, let's call it from within a simple dialplan:
exten => 123,1,Answer( )
exten => 123,2,Festival(Asterisk and Festival are working together)
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You should always call the Answer( )
application before calling Festival( ), to ensure that a
channel is established.
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As Asterisk connects to Festival, you should see
output like this in the terminal where you started the Festival
server:
[root@asterisk ~]# festival --server
server Sun May 1 18:38:51 2005 : Festival server started on port 1314
client(1) Sun May 1 18:39:20 2005 : accepted from asterisk.localdomain
client(1) Sun May 1 18:39:21 2005 : disconnected
If you see output like the following, it means
you didn't add the host to the access list in festival.scm:
[root@asterisk ~]# festival --server
server Sun May 1 18:30:52 2005 : Festival server started on port 1314
client(1) Sun May 1 18:32:32 2005 : rejected from asterisk.localdomain not
in access list
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Some people in the Asterisk community have
reported good success by passing text to Festival's text2wave utility and then having Asterisk
play back the resulting .wav file.
For example, you might do something like this:
exten => 124,1,Answer( )
exten => 124,2,System(echo "This is a test of Festival" | /usr/bin/text2wave
-scale 1.5 -F 8000 -o /tmp/festival.wav)
exten => 124,3,Playback(/tmp/festival)
exten => 124,4,System(rm /tmp/festival.wav)
exten => 124,5,Hangup( )
This method also allows you to call other
text-to-speech engines, such as the popular speech engine from
Cepstral. For this example, we'll
assume that Cepstral is installed in /usr/local/cepstral/:
exten => 125,1,Answer( )
exten => 125,2,System(/usr/local/cepstral/bin/swift -o /tmp/swift.wav
"This is a test of Cepstral")
exten => 125,3,Playback(/tmp/swift)
exten => 125,4,System(rm /tmp/swift.wav)
exten => 125,5,Hangup( )
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