Re: [codec] #7: Providing DTMF Testing Tools and Samples

"codec issue tracker" <> Sat, 10 April 2010 05:40 UTC

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Subject: Re: [codec] #7: Providing DTMF Testing Tools and Samples
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#7: Providing DTMF Testing Tools and Samples
 Reporter:  hoene@…                 |       Owner:     
     Type:  task                    |      Status:  new
 Priority:  minor                   |   Milestone:     
Component:  requirements            |     Version:     
 Severity:  Active WG Document      |    Keywords:     

Comment(by hoene@…):

 Raymond (Juin-Hwey) Chen wrote:

 > 2. Did you ever test your CODEC for other telephony signals, such as
 > /ANSam, ANS, CED, and CI tones? These tones are needed in order to
 > detect modems and fax machines and switch to an appropriate payload.
 > What about progress tones?
 > [Raymond]: No, we didn’t.  However, if these are single-frequency
 > tones, I would expect that it should be easier for a typical codec to
 > pass these tones than to pass the dual-frequency DTMF signals without
 > causing significant degradation in the subsequent processing of these

 This is pretty much a dead-end based on the other comments on this list,
 but in general, no, most of these tones are *not* single-frequency simple
 tones. ANSam, for example, is a single frequency, but is amplitude
 modulated. There are also variants that have phase reversals, and these
 must be preserved for them to be discriminated from the non-phase-reversal

 Kevin P. Fleming

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