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

I have a feeling that this requirement as it stands right now is
non-enforceable since there is no industry accepted test on DTMF pass
through.  Creating such test will not be trivial since it will require
collection of the large amount of real life DTMF and other telephony signal
recordings. So, we cannot make this a requirement for a new codec unless we
define this in a form of some minimum frequency fidelity or some other
independently verifiable quality requirement.
_____________
Roman Shpount

On Fri, Apr 2, 2010 at 4:12 PM, stephen botzko <stephen.botzko@gmail.com>wrote:

> We don't have agreed-upon tests for anything.  I've been assuming (possibly
> incorrectly) that after the requirements are understood the group will need
> to develop a test plan that indicates how we will test against the various
> requirements.
>
> Stephen Botzko
>
> On Fri, Apr 2, 2010 at 3:02 PM, Roman Shpount <roman@telurix.com> wrote:
>
>> This is all wonderful, but what seems to be missing here is any type of
>> standard test for DTMF tone detection. We have a number of tests for things
>> that should not be detected as DTMF (various talk-off tapes), but there is
>> no test with samples of valid DTMF signals. In real world you get quite a
>> variety of tones that different handsets or telephone devices generate when
>> a digit is pressed. Some of those tones are almost at border line conditions
>> for a valid DTMF tone.
>>
>> Second issue, which was already mentioned here, would be performance of
>> DTMF tone detector in the presence of packet loss or time stretching caused
>> by jitter buffer. Those things, even if they do not prevent DTMF detection,
>> are almost guaranteed to split a single long tone in two.
>>
>> Finally, we seemed to concentrate on DTMF tones only, but in reality all
>> the signaling/special tones are quite important. Fax Send/Receive tones come
>> to mind almost immediately as tones that are typically detected inband (very
>> few gateways encode those tones using RFC 4733/2833)
>>
>> I think we should formulate this requirement not in terms of DTMF tone but
>> in terms of accuracy of reproduction of  periodic signals in specified
>> frequency ranges. To be honest, the most robust solution would be to
>> incorporate RFC4733/4744 as a part of the codec in a manner similar to
>> comfort noise frames.
>> _____________________________
>> Roman Shpount - www.telurix.com
>>
>>
>> On Fri, Apr 2, 2010 at 1:34 PM, Christian Hoene <hoene@uni-tuebingen.de>wrote:
>>
>>> Hi Stephan,
>>>
>>> Comments inline:
>>>
>>>
>>> ---------------------------------------------------------------
>>> Dr.-Ing. Christian Hoene
>>> Interactive Communication Systems (ICS), University of Tübingen
>>> Sand 13, 72076 Tübingen, Germany, Phone +49 7071 2970532
>>> http://www.net.uni-tuebingen.de/
>>>
>>> From: stephen botzko [mailto:stephen.botzko@gmail.com]
>>> Sent: Friday, April 02, 2010 4:50 PM
>>> To: Christian Hoene
>>> Cc: Michael Knappe; stpeter@stpeter.im; codec@ietf.org
>>>
>>> Subject: Re: [codec] #5: Mention DTMF in requirements
>>>
>>> (a) "MUST NOT" means that it must fail.  Perhaps you meant "need not" or
>>> "might not"?
>>>
>>> CH: Yes, I meant need not (or the German „muss nicht“)
>>>
>>> (b) SHOULD is commonly used in establishing requirements, and it
>>> certainly was used in MARTINI and other working groups at IETF77 in
>>> requirements presentations with no confusion. It has a clear meaning in
>>> the requirements context (desirable but not essential) and I
>>> see no reason to avoid its use at this phase.  There will certainly be
>>> other things that are "nice to have", and it is appropriate
>>> to track them and consider them in the selection/standardization process.
>>>
>>> CH: Better? "The codec SHOULD support the transmission DTMF at most
>>> transmission conditions."
>>>
>>> I agree that language about DTMF might not need to be in the final RFC.
>>> Though if DTMF quality is known to be inadequate, it
>>> probably makes sense to tell people that.
>>>
>>> CH: Agreed. The limits of the codec shall be clearly stated.
>>>
>>> I also agree to the obvious comment that DTMF detection methods are out
>>> of scope.
>>>
>>> CH: Agreed.
>>>
>>> CH: Isn't time to include the MUST requirement for DTMF testing and
>>> SHOULD requirement for transmission support into the
>>> requirements document.
>>> Then, we could close issue #5 and continue with other things.
>>>
>>>  Christian
>>>
>>>
>>>
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>>> https://www.ietf.org/mailman/listinfo/codec
>>>
>>
>>
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>