- From: Gunnar Hellstrom <gunnar.hellstrom@omnitor.se>
- Date: Sat, 18 Jan 2014 07:45:46 +0100
- To: public-webrtc@w3.org
- Message-ID: <52DA231A.4030506@omnitor.se>
On 2014-01-18 01:53, Barry Dingle wrote: > I have attached the Australian S002 Standard for reference. Good, > > In summary, Section 5.5.1.9 (e) states: > > (i) *minimum duration* of DTMF burst (i.e. transmission) shall be *50 > ms*. And ETSI ES 201 235-2 section 4.2.4 requires 65 to75 ms. > > (ii) *minimum interval* between the transmission of digits shall be > *70 ms*. And ETSI ES 201 235-2 section 4.2.4 requires at least 65 ms and a note requiring not more than 75 ms. > > A Note says post answering DTMF signalling, digit duration should be > minimum 100 ms. How do you interpret this. Is it tone duration that should be 100 ms or tone + gap that should be 100 ms? I guess that all our use of DTMF will be "post answering". /Gunnar > > 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 <mailto: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 > <mailto: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 > <mailto: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 <mailto: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 > > > > > > > >
Received on Saturday, 18 January 2014 06:46:24 UTC