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Speech recognition for Asterisk

Speech recognition script for Asterisk that uses Google speech API.

This AGI script makes use of Google's speech recognition engine in order to render speech to text and return it back to the dialplan as an asterisk channel variable. See README for a complete list of supported languages.


Perl: The Perl Programming Language
perl-libwww: The World-Wide Web library for Perl
perl-libjson: Module for manipulating JSON-formatted data
IO-Socket-SSL: Perl module that implements an interface to SSL sockets
flac: Free Lossless Audio Codec


To install copy speech-recog.agi to your agi-bin directory.
Usually this is /var/lib/asterisk/agi-bin/
To make sure check your /etc/asterisk/asterisk.conf file


agi(speech-recog.agi,[lang],[timeout],[intkey],[NOBEEP]): Records from the current channel until 3 seconds of silence are detected (setting the 'timeout' argument to -1 disables the silence detection) or the interrupt key (# by default) is pressed. If NOBEEP is set, no beep sound is played back to the user to indicate the start of the recording. The recorded sound is send over to Google speech recognition service and the returned text string is assigned as the value of the channel variable 'utterance'.
The scripts sets the following channel variables:
utterance: The transcripted text string.
confidence: A value between 0 and 1 indicating the probability of a correct recognition.Values bigger than 0.90 usually mean that the resulted text is correct.

Asterisk dialplan examples:
In these examples googletts.agi script is used for speech synthesis:

;;Simple speech recognition
exten => 1234,1,Answer()
exten => 1234,n,agi(speech-recog.agi,en-US)
exten => 1234,n,Verbose(1,The text you just said is: ${utterance})
exten => 1234,n,Verbose(1,The probability to be right is: ${confidence})
exten => 1234,n,Hangup()

;;Speech recognition demo:
exten => 1235,1,Answer()
exten => 1235,n,agi(googletts.agi,"Say something in English, when done press the pound key.",en)
exten => 1235,n(record),agi(speech-recog.agi,en-US)
exten => 1235,n,Verbose(1,Script returned: ${confidence} , ${utterance})

;Check the probability of a successful recognition:
exten => 1235,n(success),GotoIf($["${confidence}" > "0.8"]?playback:retry)

;Playback the text:
exten => 1235,n(playback),agi(googletts.agi,"The text you just said was...",en)
exten => 1235,n,agi(googletts.agi,"${utterance}",en)
exten => 1235,n,goto(end)

;Retry in case speech recognition wasn't successful:
exten => 1235,n(retry),agi(googletts.agi,"Can you please repeat more clearly?",en)
exten => 1235,n,goto(record)

exten => 1235,n(fail),agi(googletts.agi,"Failed to get speech data.",en)
exten => 1235,n(end),Hangup()

;;Voice dialing example
exten => 1236,1,Answer()
exten => 1236,n,agi(googletts.agi,"Please say the number you want to dial.",en)
exten => 1236,n(record),agi(speech-recog.agi,en-US)
exten => 1236,n,GotoIf($["${confidence}" > "0.8"]?success:retry)

exten => 1236,n(success),goto(${utterance},1)

exten => 1236,n(retry),agi(googletts.agi,"Can you please repeat?",en)
exten => 1236,n,goto(record)

Under the folder wolfram you can find a sample agi script that in combination with speech-recog.agi sends queries to WolframAlpha and returns the answers as a dialplan variable that can be read back to the user.
See wolfram/README for details.

A diaplan example follows where you can dictate your question to WolframAplha and listen to the answer on your phone.

;WolframAlpha query demo:
exten => 1237,1,Answer()
exten => 1237,n,agi(googletts.agi,"What is your question?",en)

;;Record the question and render it to text:
exten => 1237,n(record),agi(speech-recog.agi,en-US)
exten => 1237,n,GotoIf($["${confidence}" > "0.8"]?success:retry)

;;Submit the question to wolfram:
exten => 1237,n(success),agi(wolfram.agi,"${utterance}")

;;Playback the answer:
exten => 1237,n,agi(googletts.agi,"${wolfram_answer}",en)
exten => 1237,n,goto(end)

;;Retry in case speech recognition wasn't successful:
exten => 1237,n(retry),agi(googletts.agi,"Can you please repeat more clearly?",en)
exten => 1237,n,goto(record)

exten => 1237,n(end),Hangup()


The speech-recog script for asterisk is distributed under the GNU General Public License v2.


Lefteris Zafiris (


Development snapshots that support Speech API v2 are available in either zip or tar formats.

A version that supports the new Cloud Speech API can be downloaded here.

You can also clone the project with Git by running:

$ git clone git://


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