Re: [rtcweb] Spencer Dawkins' Yes on draft-ietf-rtcweb-video-05: (with COMMENT)

Adam Roach <> Tue, 09 June 2015 20:21 UTC

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Subject: Re: [rtcweb] Spencer Dawkins' Yes on draft-ietf-rtcweb-video-05: (with COMMENT)
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On 6/9/15 12:54, Spencer Dawkins wrote:
> I did have one question. In this text:
>     Implementations MAY send and act upon "User data registered by Rec.
>     ITU-T T.35" and "User data unregistered" messages.  Even if they do
>     not act on them, implementations MUST be prepared to receive such
>     messages without any ill effects.
> Is that a usual thing to say? Perhaps it is, but I thought that might be
> understood.

This text is the result of a specific recommendation from Stefan Wenger, 
who has far more familiarity with what H.264 implementors are likely to 
get wrong than I do. His suggestion (to the RTCWEB mailing list, 
November 24, 2014) was:

> MAY:
> User data T.35 registered, and user data unregistered
> Especially the latter you see occasionally for proprietary extensions.
> It's a good idea to advise implementers that a bitstream may contain that
> kind of stuff, even if they don't act on it. 

Given Stefan's specific mention of this as a potential issue, I'm 
inclined to leave it in unless someone can provide a reasonable argument 
that it causes harm.