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Re: [MMUSIC] T.140 in Data Channel scenarios - SDP support- the pull request

Bernard Aboba <bernard.aboba@gmail.com> Fri, 27 September 2019 11:03 UTC

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From: Bernard Aboba <bernard.aboba@gmail.com>
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Date: Fri, 27 Sep 2019 04:03:17 -0700
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References: <667F39A8-C0DD-45E5-B48C-D57A6FAB87C0@ericsson.com>
Cc: Gunnar Hellström <gunnar.hellstrom@omnitor.se>, mmusic WG <mmusic@ietf.org>
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To: Christer Holmberg <christer.holmberg@ericsson.com>
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Subject: Re: [MMUSIC] T.140 in Data Channel scenarios - SDP support- the pull request
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I do not understand the PR. 

> On Sep 27, 2019, at 2:41 AM, Christer Holmberg <christer.holmberg@ericsson.com> wrote:
> 
> 
> https://github.com/cdh4u/draft-datachannel-t140/pull/35
> 
> JSEP has a statement in section 5.2.1  https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-25#section-5.2.1 about creation of an offer for a data channel saying
> 
> "Attributes other than the ones specified above MAY be included"
> 
[BA] No existing browser generates the attributes defined in the draft in createOffer(). Since the SDP cannot be changed, that also means that if you pass the draft attributes to SLD/SRD these calls will fail.
> So, to me it seems that the API and JSEP together not really supports, but also not forbids use of additional attributes in data channel specifications.
> 
[BA] That is not correct. If you pass the draft attributes to SLD/SRD all browsers will fail.
> Therefore, the discussed note seems too strong
> 

The note is correct as written. What could be clarified is that if support for the attributes can be handled in the application, browser support is not required.

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