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Re: [rtcweb] Does RID require the same ext id for all the m= sections?

"Mo Zanaty (mzanaty)" <mzanaty@cisco.com> Mon, 11 September 2017 13:34 UTC

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From: "Mo Zanaty (mzanaty)" <mzanaty@cisco.com>
To: Iñaki Baz Castillo <ibc@aliax.net>
CC: "rtcweb@ietf.org" <rtcweb@ietf.org>
Thread-Topic: [rtcweb] Does RID require the same ext id for all the m= sections?
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Date: Mon, 11 Sep 2017 13:34:27 +0000
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Subject: Re: [rtcweb] Does RID require the same ext id for all the m= sections?
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See bundle section 13.

https://tools.ietf.org/html/draft-ietf-mmusic-sdp-bundle-negotiation-38#section-13

The same ID must always map to the same URN. Different IDs can map to the same URN as aliases. (The latter is not stated but implied.)

Mo

On Sep 11, 2017, at 8:49 AM, Iñaki Baz Castillo <ibc@aliax.net<mailto:ibc@aliax.net>> wrote:

On Sun, Sep 10, 2017 at 8:22 PM, Mo Zanaty (mzanaty) <mzanaty@cisco.com<mailto:mzanaty@cisco.com>> wrote:
All extmap IDs must be consistent in all bundled m= sections, just like PTs.

Thanks.

However, what does "consistent" mean? I assume/expect that the extmap
ID (for example a=extmap:4) cannot exist in two different m= sections
pointing to different extension URLs, right?

But, and given that you told about PTs, it's perfectly valid that two
different PTs point to the same codec+condiguration within the same m=
section or in different m= sections.

So, could a m=audio section have an "a=extmap:4 urn:foo" line while a
m=video section has "a=extmap:8 urn:foo"? or should both use extmap ID
4?

For example, the extmap ID for MID must be *UNIQUE* across all the
m=sections. Does the same constrain exist for the extmap ID for RID?



--
Iñaki Baz Castillo
<ibc@aliax.net<mailto:ibc@aliax.net>>

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