- From: Gunnar Hellstrom <gunnar.hellstrom@omnitor.se>
- Date: Sat, 18 Jan 2014 22:35:04 +0100
- To: Barry Dingle <btdingle@gmail.com>
- CC: "public-webrtc@w3.org" <public-webrtc@w3.org>
- Message-ID: <52DAF388.9040708@omnitor.se>
On 2014-01-18 10:41, Barry Dingle wrote: > > > On Sat, Jan 18, 2014 at 5:45 PM, Gunnar Hellstrom > <gunnar.hellstrom@omnitor.se <mailto:gunnar.hellstrom@omnitor.se>> wrote: > > 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. > And the maximum limit was for use during supplementary services. > > >> >> (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". > > > I took that to mean duration of tone Burst (i.e. NOT including the gap > between tone bursts. > Yes, that sounds to be the most likely interpretation. So, then we have guidance to the default values: The default tone duration should be 70 ms to follow ETSI or 100 ms to follow Australia. ( because the usage will be "post answering" ) ( the 70 ms figure appears n many other sources as a suitable value. I suggest that that is selected if Australia can confirm that it can be used. ) The default gap should be 70 ms ( for both ETSI and Australia ) /Gunnar > /Barry > > > /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 21:35:42 UTC