Peter Saint-Andre wrote:
Paul Witty wrote:
Peter Saint-Andre wrote:
I already have support for
in-band DTMF, and, once I've written the stuff to negotiate it, will
support RFC 4733 DTMF in the content channel. I'll also implement DTMF
in the signalling channel.
I see two options:
1. DTMF over XMPP (XEP-0181) ("in-band/signalling")
2. DTMF over RTP (RFC 4733) ("out-of-band/media")
Do you see a third option?
DTMF actually as tones in the audio. Old-fashioned, but valid enough
for G.711, and probably some other codecs as well. Sometimes needed if
going to a SIP to POTS gateway, and not a bad fallback if the far end
doesn't offer support for XEP-0181 or RFC 4733.
Ah, OK, I got confused by terminology. Typically people call the
"signalling channel" something like SIP or XMPP (where you negotiate the
media session) and the "media channel" something like RTP (the transport
for the media). You're talking about sending DTMF as tones in the media
itself. Yes, that's old-fashioned, but it probably gets the job done. :)
I'd consider DTMF tones in the audio to be the only in-band method, with
RFC 4733 being out-of-band as it is the same channel but different band
as the media, and XEP-0181 being out-of-band as it is in a different
channel to the media. I may have a slightly video-conferencing view of
the world though.
For a bit of a laugh, I've also implemented DTMF through chat messages
(as well as a very basic chat-based UI to connect to pre-defined
destinations through the gateway), in order to let released versions of
Google Talk send messages.
--
Paul
