W3C's feedback on RTT for WebRTC in EN 301 549

Dear WebRTC Working Group,

It was brought to the attention of the Working Group chairs that the 
ongoing revision of EN 301 549 (a EU norm on accessibility) is looking 
at integrating considerations on how to add real-time text (RTT) to 
WebRTC-mediated calls. The current text there makes references to 
RFC8865 "T.140 Real-Time Text Conversation over WebRTC Data Channels".

As has emerged in recent discussions on the WebRTC repo [1], there seems 
to be significant concerns in how good a fit RFC 8865 is for integration 
of RTT in browser-based WebRTC sessions.

As a result, the WebRTC Chairs and Staff Contacts are proposing that W3C 
should offer the following comment to the EN 301 549 draft committee 
(where W3C has an observer seat):

RFC 8865 lacks important RTP packets fields for the synchronization of 
real-time audio and video with RTT. RFC 8865 is ambiguous as to what 
gateways need to do if there are holes due to losses when receiving RFC 
4103 packets.To W3C´s knowledge, there is no mainstream implementation 
of RTT using RFC 8865.

Until there is agreement on whether RFC 8865 is suitable and reliable 
for RTT within WebRTC, W3C strongly recommends to qualify references to 
RFC 8865 within EN 301 549.
(where qualifying references would e.g. include noting some of these 

Please let us know if you have any concerns with this, before Feb 21 EOB.



1. https://github.com/w3c/webrtc-pc/issues/2931

Received on Thursday, 15 February 2024 09:00:54 UTC