Re: [rtcweb] DTMF usecase before DTMF API [was RE: The DTMF API]

[Matthew Kaufman <[e-mail]>]

On 11/18/11 11:02 AM, Hadriel Kaplan wrote:
> On Nov 17, 2011, at 9:46 PM, Harald Alvestrand wrote:
>>>   AFAIK, DTMF is not directly going to useful in browser-browser scenario and it is possible to pass DTMF in the signaling layer for H.323, SIP in the standard manner.
>> What do you mean by "the standard manner"?
> H.323 and SIP both offer a signaling-plane means of indicating DTMF, other than RFC 2833/4733.  For H.323 it's H.245 User Input Indications (UII) messages.  For SIP it's officially KPML (RFC 4730), but in practice it's not popular.  Two vendors I know of support it, but it's a drop in the bucket compared to rfc2833 or SIP INFO.
>

With no DTMF work in the browser, the browser could still send any 
signaling-plane version of DTMF it wants in cooperation with whatever 
server(s) it is talking to.

However this would preclude all cases where the DTMF must be transported 
in the media plane, as per 2833/4733.

Given that the latter cases are fairly common (and not just for PSTN 
interoperation) I believe it would be a mistake to not have this 
capability in the browser. Noting that if we do require it, we get the 
best of both worlds... the ability for the JavaScript to command the 
browser to insert RFC4733 DTMF in the media stream *and* the ability for 
the JavaScript to notify the server to send signaling-layer DTMF.

Matthew Kaufman