Text Conversation standards report

Gunnar Hellstrom gunnar.hellstrom at OMNITOR.SE
Mon Oct 25 17:25:06 EDT 1999

Gunnar Hellström
October 23, 1999

This is a report from accessibility related activities in ITU-T Q11-15/16
meeting in Red Bank, New Jersey 1999-10-18—22.

in the Multimedia Systems and Services ITU-T Q11-15/16 meeting in Red Bank,
NJ, I have participated with a set of accessibility related contributions
from LM Ericsson.
The contributions can be downloaded from
The meeting was successful and the results point towards major achievements
in approved accessibility related standards in February 2000.

1       Total Conversation and Text Telephone Services
A definition of the Total Conversation Service concept is made in a draft
multimedia service description F.MCVS, as an extension of the video phone
and video conferencing concept, by adding real time text conversation to it.
The F.MCVS draft is numbered APC-1690a. It was reviewed briefly. Q1/16 is
supposed to bring it to the next SG16 meeting for determination. The Text
Telephone Service is also defined here.

2       Text Conversation in IP Multimedia Conversation and IP Text Telephony
Telecommunication is moving into the IP networks. Standardised text
conversation must be established there as well as it was in the PSTN as text
telephony. One main architecture for IP Multimedia and IP Telephony is ITU-T

Text conversation is added by H.323 Annex G, Text Conversation and Text SET.
It also defines a simple IP text telephone with text and voice features. A
revised version of the document was reviewed in the meeting, and approved.
It was submitted as a white contribution to ITU-T in Geneva for decision in
the February 2000 SG16 meeting. The submitted document is found as TD-60.
The main change from last version was that RTP transport of text is now
default and TCP is a preferred option. Also the H.245 message syntax is more

For IP transmission of text conversation, an IETF document “RTP-Text” is in
the process of being approved. It was reviewed as APC-1689. After checking
that it matched the H.323 Annex G progress, it was slightly modified and
entered as a contribution for next IETF meeting in Washington DC on November
10. It can be found in Internet-Drafts as ietf-draft-avt-rtp-text-02.txt

For the purpose of defining the text conversation presentation protocol
T.140 as the contents of RTP-Text, T140 is applied for MIME registration as
a media stream of the text type, both with and without the enclosing RTP
payload description.

When the MIME registration is complete, it is possible to make IP text
telephones and IP Total Conversation devices also according to the IETF SIP
architecture without any need for further standardisation.

3       Interworking with text conversation in different networks
H.248 is an important gateway architecture in creation. It will enable calls
to efficiently cross the border between IP networks and other environments,
like PSTN and mobile networks. It is important to define how that is to be
done for text conversation and text telephony.
H.248 is structured in a core document and packages that add specific
application information. The creation of H.248 is a joint project between
ITU and IETF and the core document will be published also as an IETF
Text Conversation and Text Telephone packages are proposed in H.248 Annex I.
It was entered as APC-1691 to the meeting, and refined into TD-55a. Time did
not allow for a thorough review of it.
The Core H.248 was approved to go for decision in February. The general
format for package definition has been varying and was still varying in the
meeting. It was not regarded stable, and therefore only a few very central
packages were approved for decision. The other packages, including Annex I,
were recommended for determination in February.
The text conversation packages will be entered together with other basic
packages in one document to the Megaco working group of IETF for the meeting
in Washington DC in November. Mike Kallas of Nortel Networks is the editor
of the combined document.

4       Text Conversation in ISDN
The approved modification to H.320 multimedia in ISDN to carry text
conversation in a H.224 transport channel was again discussed in Q11/16. The
required full new text of H.224 and the modification instructions were
submitted to ITU for decision via Tom Geary, rapporteur of Q11/16.

5       Text included in the video stream
The advanced video coding activity H.26L works on a definition of how small
amounts of real time text can be transferred in the video stream. They were
adviced to use ISO 10646 UTF-8 coding and some kind of usage indicator, that
can indicate the application: text description of video, video subtitling,
text conversation, copyright info etc.

6       New question definitions
The proposed new question definitions for 2001-2004 were briefly reviewed.
Question H is a broadened Accessibility question. The proposed project
Mediacom 2004 also includes Accessibility studies. It is important to find
out if the ITU members are prepared to put resources into the proposed work
items of the Accessibility activities. The definitions are found in
APC-1680, TD-11, and TD-12.

7       Conclusion
If everything goes smoothly, the Total Conversation concept can be complete
by February 18, 2000. That will allow any interested organisation to create
standardised interworking telecommunication services including text
conversation. If properly exploited, it will be a major achievement for
anyone, but especially for deaf, hearing impaired, speech impaired and
deafblind people. The gateway definition will only be Determined in February
and are expected to be Decided later during 2000 together with other H.248
gateway additions.
The standards are backwards compatible with earlier telecom services and
·       Text telephony in PSTN, IP and mobile networks, including concurrent use
of voice and text.
·       Total conversation in PSTN, ISDN, IP, data conferencing and mobile
networks allowing simultaneous real time conversation in video, text and
Gunnar Hellström
LM Ericsson

Mob +46 708 204 288
Tel +46 8 556 002 03
Fax +46 8 556 002 06
Video +468 556 002 05
Txt (All kinds) +46 8 556 002 05
E-mail gunnar.hellstrom at omnitor.se

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