- From: Barry Dingle <btdingle@gmail.com>
- Date: Sat, 18 Jan 2014 11:53:22 +1100
- To: Gunnar Hellstrom <gunnar.hellstrom@omnitor.se>
- Cc: "Cullen Jennings (fluffy)" <fluffy@cisco.com>, Mike Johns <m.johns@commsalliance.com.au>, "public-webrtc@w3.org" <public-webrtc@w3.org>
- Message-ID: <CAN=GVAvHhmFG-C5XvY9BJYdn0kk16hn76bAG=2yZsEOsmPUBBQ@mail.gmail.com>
I have attached the Australian S002 Standard for reference. In summary, Section 5.5.1.9 (e) states: (i) *minimum duration* of DTMF burst (i.e. transmission) shall be *50 ms*. (ii) *minimum interval* between the transmission of digits shall be *70 ms*. A Note says post answering DTMF signalling, digit duration should be minimum 100 ms. I *cannot* find a reference to a minimum 125 ms tone + gap time Or to a maximum 'signalling rate' of 8 digits per sec (that equals 125 ms). Cheers, /Barry Barry Dingle "Australia" On Sat, Jan 18, 2014 at 8:39 AM, Gunnar Hellstrom < gunnar.hellstrom@omnitor.se> wrote: > On 2014-01-17 18:35, Cullen Jennings (fluffy) wrote: > >> I’m fine with lower limits allowing people to shoot themselves in the >> feet but I want the defaults to be safe for most cases. >> >> So the way I think we should set this is to set the default to be "safe" >> for all major deployments world wide. And have the minimum values allow >> you set it to be as low as is usable in any any major deployment world >> wide. With that strategy, and the information folks provided in this email >> thread, I think we get to the following. >> >> How about this for a proposed change: >> >> We change the min tone time to 40 ms. >> >> We change the min gap time to 30 ms. >> >> We change the default gap to 70 ms (this meets Australia AS/CA S0020) >> >> We leave the default tone duration at 100 ms. >> > Why this long tone? All columns show minimum 40 ms for duration. > > If you want to guarantee the minimum total length of tone + gap to be 125 > ms as required by Australia, it would make more sense to set the default > tone to 55 ms. > Then default tone + default gap is 125 ms, and this is also very close to > the maximum rate set by Japan and Brazil. > > Regarding all problems with misbehaving echo cancellers in VoIP gateways, > I think it is good to not push these figures to its extremes. > > So, my proposals for default figures are 55 ms tone and 70 ms gap. > > And minimums as Cullen's proposal. > > /Gunnar > > >> Does that change look OK to folks? >> >> >> >> >> On Jan 17, 2014, at 6:26 AM, Barry Dingle <btdingle@gmail.com> wrote: >> >> Thanks for helpful reply Gunnar. >>> >>> The Australian DTMF specification in included in AS/CA S002. The current >>> version of S002 'still' states that DTMF tones should have a minimum 70 ms >>> gap. The min DTMF Gap value has not changed because of PSTN network >>> equipment and some older Customer Equipment including IVR. >>> >>> I have informed the organisation (Communications Alliance) that reviews >>> S002 of the WebRTC interest in setting consistent DTMF tone and gap >>> durations and that it might impact operation involving Australian approved >>> equipment. >>> >>> Barry Dingle >>> "Australia" >>> >>> >>> On Fri, Jan 17, 2014 at 6:11 PM, Gunnar Hellstrom < >>> gunnar.hellstrom@omnitor.se> wrote: >>> On 2014-01-17 01:43, Roman Shpount wrote: >>> >>>> I was the person who asked for this change. >>>> >>>> Based on http://www.itu.int/rec/T-REC-Q.24-198811-I/en Annex A, valid >>>> tone duration is 40 ms and up. Valid gap duration is 30 ms (minimal for >>>> Japan) and up to 70 ms minimum in Australia. So, my suggestion was to keep >>>> defaults at their current values but allow to set minimal values to minimal >>>> possible legal values (40 ms tone and 30 ms gap). My justification is that >>>> DTMF is a legacy interop feature and it should be able reproduce any legal >>>> DTMF string which can occur in the wild by modifying the JavaScript >>>> parameters. >>>> >>> The same table in Q.24 has a value for signal velocity, that is the >>> minimal sum of a tone and a gap. Figures are between 93 and 125 ms, with 93 >>> for USA, 100 ms for Europe, 120 for Japan and Brazil and 125 for Australia. >>> That would require for example 50 tone and 50 pause to cover USA and >>> Europe, and 50 tone and 75 pause to cover all. >>> >>> Since RFC 4733 should be used for the transmission and detection of >>> DTMF, one could expect to rely on RFC 4733 for the timing. In section 3.1 >>> it refers to Q.24 and points out 40/40 but a limit of 8 to 10 digits per >>> second. That would be accomplished for example by 50 tone and 70 pause. >>> >>> It would be interesting to know if there are any international >>> experience from setting parameters for RFC 4733 usage that we could use. >>> >>> We should also remember that Q.24 is talking about timing for detection >>> at the receiving end. So, some tolerance should be given at the generating >>> end. >>> >>> So, it seems that 50 tone and 50 pause would be good timing for >>> transmission except for Australia, Brazil and Japan ( if the Q.24 limits >>> are still valid in these countries ). >>> >>> Gunnar >>> >>> >>> >>> _____________ >>>> Roman Shpount >>>> >>>> >>>> On Thu, Jan 16, 2014 at 7:19 PM, Cullen Jennings (fluffy) < >>>> fluffy@cisco.com> wrote: >>>> >>>> This has been sitting on the editors todo list for a long time and I >>>> wanted to try and sort it out … >>>> >>>> The gap between DTMF digits is currently specified at 50ms. Long ago >>>> someone requested we change this to 40 ms. >>>> >>>> Does anyone remember why people wanted to make this change? Thought on >>>> if it should be 40 or 50? >>>> >>>> Thanks, Cullen >>>> >>>> >>>> >>>> >>>> >>> > >
Attachments
- application/pdf attachment: S002_2010.pdf
Received on Saturday, 18 January 2014 00:54:13 UTC