Re: DTMF v4

WebRTC-SIP Interworking Requirements Draft states that:

A3-4 WebRTC MUST provide a means for the Javascript application to invoke
[RFC4733] DTMF events to be generated, and their duration, with a default
duration of 100ms.

A3-6 WebRTC MUST NOT generate [RFC4733] events closer than 50ms
back-to-back.  In other words, even if                      the Javascript
calls the API repeatedly or provides a string of digits to send, the
browser must enforce a minimum of 50ms inter-event gap.

There are several fairly old recommendations, such as ITU-T V.18, on which
these values are based, but the bottom line that these values are usually
considered safe.

_____________

Roman Shpount

On Fri, Dec 14, 2012 at 3:53 PM, Martin Thomson <martin.thomson@gmail.com>wrote:

> On 14 December 2012 12:40, Harald Alvestrand <harald@alvestrand.no> wrote:
> > Bernard mentioned a minimum gap (I think he said 50 ms), but I'm not sure
> > where that came from.
>
> Minimum values come from experience with IVR interoperation for cases
> where the tone is subsequently mixed into the audio.  Too short a tone
> (or gap) and some IVRs fail to detect the tone.  I've seen minimum
> tone duration of 100ms and gap of 50ms in some cases, though more
> conservative values might be appropriate.  I have no good data to back
> any specific choice.  I expect fluffy has more data than I.
>
>