[asterisk-speech-rec] How to enable N-Best decoding?

[Stephen Keller]

Scott (and anyone else interested in n-best),

I apologize for the delay in this response, but we've been working with
Digium on troubleshooting some issues related to n-best using the
LumenVox Speech Engine on Asterisk. It looks like we have them all
straightened out, and the latest version of the Asterisk-LumenVox
connector bridge is available on our FTP site (as always drop me a line
off-list if you need the link).

To activate N-best, use Set(SPEECH_RESULTS_TYPE()=nbest) after
SpeechCreate. 

You can then check results like normal, except you specify different
results using ${SPEECH_TEXT(X/Y)}, where X is the number of the result
to check (starting at zero) and Y is the interpretation.

So the first interpretation for the first n-best result is 0/0; e.g.
${SPEECH_TEXT(0/0)}. If there is more than one semantic interpretation,
you would check 0/1. The second n-best result would be 1/0, etc.

Likewise you would use ${SPEECH_SCORE(X/Y)} in the same fashion to check
confidence scores.

Here's a  very basic dial plan and grammar that should illustrate the
concepts. If you use the grammar and say a valid choice, you will almost
certainly get back multiple n-best results, since all the words are very
similar.

exten => 1,1,Answer
exten => 1,n,Wait(1)
exten => 1,n,SpeechCreate
exten => 1,n,Set(SPEECH_RESULTS_TYPE()=nbest)
exten => 1,n,SpeechActivateGrammar(test) 
exten => 1,n,SpeechBackground(beep) 
exten => 1,n,Verbose(1,Number of results: ${SPEECH(results)}) 
exten => 1,n,Verbose(1,First result is ${SPEECH_TEXT(0/0)} with a
confidence score of ${SPEECH_SCORE(0/0)}) 
exten => 1,n,Verbose(1,Second result is ${SPEECH_TEXT(1/0)} with a
confidence score of ${SPEECH_SCORE(1/0)}) 

Test grammar:

#ABNF 1.0 UTF-8;

language en-US;
mode voice;
tag-format <semantics/1.0>;

root $rootrule;

$rootrule = $she | $sea | $he | $bee;

$she = she;
$sea = sea;
$he = he;
$bee = bee;

--
Stephen Keller
LumenVox Support
P: 877-977-0707, just say "Support"
F: 858-707-7072
Support at LumenVox.com
www.LumenVox.com



Winner "Best Innovation in Speech Recognition"
AVIOS SpeechTEK Award

 


> -----Original Message-----
> From: asterisk-speech-rec-bounces at lists.digium.com 
> [mailto:asterisk-speech-rec-bounces at lists.digium.com] On 
> Behalf Of Scott Stingel
> Sent: Monday, April 30, 2007 9:38 AM
> To: asterisk-speech-rec at lists.digium.com
> Subject: [asterisk-speech-rec] How to enable N-Best decoding?
> 
> Hello-
> 
> I'm running the Lumenvox 7.5 engine, the Lumenvox 1.4 connector, and 
> Asterisk 1.4.3.   All is well, except that the N-Best feature 
> does not 
> seem to work.  As I understand it, this feature allows the 
> recogniser to return multiple possibilities for the decoded 
> recognition.
> 
> What do I have to do to enable this?   An excerpt from the 
> DecodeServerLog.txt file shows these interesting lines before 
> each decode.  Perhaps the "NO_OOV" is important?
> 
> 04/30/2007 
> 09:28:12,860,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0] Begin 
> Decode Using Context-Free Grammar
> 04/30/2007 09:28:12,861,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0]
> Loading Context Free Gramamr
> 04/30/2007 09:28:12,863,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0]
> Retrieving words
> 04/30/2007 
> 09:28:12,864,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0] Word 
> retrieval time: 0
> 
> 04/30/2007 
> 09:28:12,864,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0] Load 
> grammar time: 0ms
> 04/30/2007 09:28:12,865,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0]
> Context-Free Grammar Activated: 5 ms
> 04/30/2007 09:28:12,865,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0]
> LumenVox(161): LM("NO_OOV") deleted
> 
> 04/30/2007 
> 09:28:12,876,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0] LM= "NO_OOV"
> 
> 04/30/2007 
> 09:28:12,877,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0] nbest 
> will not be used on this decode run
> 04/30/2007 
> 09:28:12,877,0,[AmericanEnglish][MODEL_LOW:ThreadNdx:0] Begin 
> Core Decode Port
> 
> Thanks for any help,
> Scott Stingel
> 
> www.evtmedia.com
> 
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