How do I get Microsoft DTMF Recognizer engine to return more than one tone?

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This refers to the DTMF Recognition Engine that is part of the Microsoft Speech Recognition Engine V11 package.

After much head scratching I managed to get the engine to recognize the first tone that I added using the AddTone((byte)tone) (regardless of how many tones I add).

If I send a series of audio tones it only returns the one that I added to the engine first.

Example 1: I add all the tones from 0 to 9 using AddTone((byte)tone);
I send an audio stream containing a series of DTMF tones from 0 to 9.
The engine returns 0 only.

Example 2: I add all the tones from 9 to 0 using AddTone((byte)tone);
I send the same audio stream containing a series of DTMF tones from 0 to 9.
The engine returns 9 only.

What am I missing?

Posted 4-Aug-15 20:36pm

Herbie Mountjoy

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arussell · Answer 1 · 2015-08-05T10:21:00

Solution 1

What grammar did you load?

AddTone() is used add tones to be recognized against the current grammar.

Posted 5-Aug-15 10:21am

arussell

Herbie Mountjoy · Answer 2 · 2015-08-05T16:58:00

Here is the grammar, copied from MSDN.  I'm afraid the online help doesn't explain how this is supposed to work.  

I am guessing (I know, bad idea) that a queue of tones will create a container full of results.  If so, where is the container?



<grammar mode="dtmf" root="digit" version="1.0">
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://www.w3.org/2001/06/grammar 
                             http://www.w3.org/TR/speech-grammar/grammar.xsd"
         xmlns="http://www.w3.org/2001/06/grammar">

<rule id="digit">
 <one-of>
   <item> 0 </item>
   <item> 1 </item>
   <item> 2 </item>
   <item> 3 </item>
   <item> 4 </item>
   <item> 5 </item>
   <item> 6 </item>
   <item> 7 </item>
   <item> 8 </item>
   <item> 9 </item>
 </one-of>
</rule>

<rule id="pin" scope="public">
 <one-of>
   <item>
     <item repeat="4"><ruleref uri="#digit" /></item>
     #
   </item>
   <item>
     * 9
   </item>
 </one-of>
</rule>

</grammar>