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

From: "codec issue tracker" <[email-masked]>
Date: Sat, 03 Apr 2010 04:55:05 -0000

#7: Providing DTMF Testing Tools and Samples
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 Reporter:  hoene@…                 |       Owner:     
     Type:  task                    |      Status:  new
 Priority:  minor                   |   Milestone:     
Component:  requirements            |     Version:     
 Severity:  Active WG Document      |    Keywords:     
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 To verify the performance of DTMF transmission, a DTMF Testing Suite would
 be useful.

 Requirements include:
 - Support DTMF and optinal other signalling tones.
 - Automatic testing.
 - Available under similar terms as the CODEC.
 - Availablity preferable before finishing the IETF Codec Requirements
 document.

-- 
Ticket URL: <https://svn.tools.ietf.org/wg/codec/trac/ticket/7>
codec <http://tools.ietf.org/codec/>

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From: "codec issue tracker" <[email-masked]>
Date: Sat, 10 Apr 2010 05:39:10 -0000

Comment(by hoene@…):

 Koen Vos:

 It's unclear what to test about DTMF though. The Codec will support a
 range of sample rates and bitrates. The requirements specify coding of
 music at near-transparent quality. I don't see how a such a codec could
 not provide sufficient quality for in-band DTMF. At the same time, the
 requirements talk about bitrates down to 8 kbps, where it may be quite
 tricky to get DTMF to work well. Therefore, specifying that the codec
 SHOULD or MUST encode DTMF with sufficient quality is meaningless. If
 anything, the bitrate settings that allow in-band DTMF could be
 characterized after the Codec is formed.

 Nevertheless it's good to be aware of these use cases during development.
 For instance, with SILK we included DTMF signals in the LSF quantizer
 training database.

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/codec/trac/ticket/7#comment:1>
codec <http://tools.ietf.org/codec/>

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From: "codec issue tracker" <[email-masked]>
Date: Sat, 10 Apr 2010 05:40:17 -0000

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
 tones.

 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
 versions.

 --
 Kevin P. Fleming

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/codec/trac/ticket/7#comment:2>
codec <http://tools.ietf.org/codec/>

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From: "codec issue tracker" <[email-masked]>
Date: Sat, 10 Apr 2010 05:40:47 -0000

Comment(by hoene@…):

 [Raymond]: We can use real-world recorded DTMF signals if we want to, but
 we don’t have to. Yes, in our DTMF testing of BV16 we used a DTMF
 generator software to generate the waveform of 20,000 random DTMF symbols
 for each of 24 DTMF test conditions, for a total of nearly half a million
 DTMF symbols. After passing through the codec, the DTMF signals were
 passed through a PC executable program which simulated a DTMF decoder that
 was widely deployed in commercial VoIP applications. The decoded DTMF
 symbols were then compared with the original DTMF keys used to generate
 the symbols to calculate the error rates. As you can see, such a test
 method is purely based on software and can easily be duplicated by third
 parties.  If the codec WG decides not to do anything with DTMF, then
 obviously nothing further needs to be done, but if the WG decides that the
 codec candidate needs to be tested for DTMF pass-through, I will try to
 dig up our DTMF test software package and get internal approval to donate
 it to IETF for this purpose.

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/codec/trac/ticket/7#comment:3>
codec <http://tools.ietf.org/codec/>