Subject: [Sipping] [mmusic] Inclusion of media type = "text" in SDP

From: "Gunnar Hellstrom" <[email-masked]>
Date: Fri, 14 Nov 2003 12:24:12 -0600

This is a request for a minor addition to draft-ietf-mmusic-sdp-new-15.txt
to acknowledge use of the media type "text" in sessions.

An RTP transport for real time character by character transmission of text
was defined a couple of years ago in RFC2793.
It is now successfully used in conversational applications, usually combined
with voice and/or video to enable the participants in the session to
communicate in any preferred medium. One important user group is deaf and
hard-of-hearing people, but the feature is of course of value for all.

In the past, most multimedia implementors have been eager to create
interoperability in video and audio, while the text part has been left
behind and iimplemented as manufacturer specific message-oriented
"chat"-additions. It is time for a change, to raise all the three media of
video, text and audio to the same status of interoperability and deployment.
That will give SIP based conversational services a real benefit.

This is also needed for the transcoding work.

By mistake no registration of "text" as an allowed media in the m=
descriptor of SDP has yet taken place. This was discussed in the mmusic
meeting today, and the conclusion was that since it is already a MIME top
level medium, it is just a matter of including it in the sdp document to
make it allowed.

Therefore I suggest the addition of the word "text" in the following three
places in draft-ietf-mmusic-sdp-new-15.txt .
In discussion with Colin, we came to the conclusion that this action would
be sufficient for acknowledging the text medium.

--------in section 5.14 ----------------------------------------------
5.14 Media Announcements ("m=")

      m=<media> <port> <transport> <fmt list>

   A session description may contain a number of media descriptions.
   Each media description starts with an "m=" field, and is terminated
   by either the next "m=" field or by the end of the session
   description. A media field has several sub-fields.

   The first sub-field is the media type.  Currently defined media are
   "audio", "video", "text", "application", "data" and "control", though
this
   list may be extended in future.

-----further down, same section -----------

   The fourth and subsequent sub-fields are media formats.  For audio
   text and video, these SHOULD reference a MIME sub-type describing the
   format under the "audio", "text" and "video" top-level MIME types.

------In Appendix A------------------------------

; sub-rules of 'm='
      media =               token
                            ;typically "audio", "video", "text",
"application"
                            ;or "data"
------End of
proposal--------------------------------------------------------------------
--------

Regards

Gunnar
-------------------------------------------
Gunnar Hellström
Omnitor AB
Renathvägen 2
SE 121 37 Johanneshov
SWEDEN
+46 8 556 002 03
Mob: +46 708 204 288
www.omnitor.se
[email-masked]
--------------------------------------------

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---

From: Dave Singer <[email-masked]>
Date: Sun, 16 Nov 2003 12:32:04 -0800

There is also the 3G timed text draft, of course, 
and the upcoming MPEG and W3C work in timed text.

At 12:24 PM -0600 11/14/03, Gunnar Hellstrom wrote:
>mmusic mailing list
>[email-masked]
>https://www1.ietf.org/mailman/listinfo/mmusic

-- 
David Singer
Apple Computer/QuickTime