Re: [codec] #5: Mention DTMF in requirements

Brian West <brian@freeswitch.org> Fri, 02 April 2010 21:32 UTC

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From: Brian West <brian@freeswitch.org>
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Date: Fri, 02 Apr 2010 16:14:41 -0500
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To: "Raymond (Juin-Hwey) Chen" <rchen@broadcom.com>
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Subject: Re: [codec] #5: Mention DTMF in requirements
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The biggest issue with relaxed DTMF is screaming kids can trigger stray DTMF detection as can some people's voices.

/b

On Apr 2, 2010, at 3:54 PM, Raymond (Juin-Hwey) Chen wrote:

> Actually, ITU-T Recommendation G.720 gives some guidelines about how to test a codec’s performance when passing DTMF signals through in-band.  (It also talks about other non-voice signals.)
>  
> In practice, however, we found that some of the test conditions specified in G.720 are fairly extreme corner cases which you normally don’t see in real-world recorded DTMF signals.  Real-world DTMF signals are usually easier to pass through a codec without degradation in the DTMF detection error rate than those extreme DTMF conditions specified in G.720.
>  
> In our BroadVoice16 paper that I mentioned previously, we described a method for testing DTMF pass-through performance for a codec.  The method is based on G.720 but with some relaxation of the extreme conditions to better reflect the DTMF conditions we observed in a large amount of real-world record DTMF signals.  This is because we are more interested in how a codec would perform when passing typical real-world DTMF signals through.
>  
> Raymond
>