Re: [MMUSIC] "a=extmap" with BUNDLE

Byron Campen <docfaraday@gmail.com> Mon, 27 March 2017 17:55 UTC

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To: Taylor Brandstetter <deadbeef@google.com>, =?UTF-8?Q?I=c3=b1aki_Baz_Castillo?= <ibc@aliax.net>
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From: Byron Campen <docfaraday@gmail.com>
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Date: Mon, 27 Mar 2017 12:55:27 -0500
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Subject: Re: [MMUSIC] "a=extmap" with BUNDLE
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     Would it not be sufficient to specify that bundled m-sections not 
use the same identifier for _different_ extensions? There's no ambiguity 
if you use '3' for mid on every m-section, which is the kind of thing 
implementations do now anyway.

Best regards,
Byron Campen

On 3/27/17 12:44 PM, Taylor Brandstetter wrote:
> If extension IDs aren't unique across bundled m= sections, then on 
> receiving a packet, an implementation may need to determine which m= 
> section it's "associated" with before knowing how to interpret the 
> extension IDs. To do this, it may need to use the MID, which means 
> that at a minimum, the MID extension must be using a unique ID.
>
> But this increases implementation complexity without much benefit (the 
> benefit being that by sharing IDs, you could more easily avoid running 
> out of spare IDs). So I'd be in favor of just requiring them to be unique.
>
> On Sat, Mar 25, 2017 at 6:35 PM, Iñaki Baz Castillo <ibc@aliax.net 
> <mailto:ibc@aliax.net>> wrote:
>
>     2017-03-24 19:28 GMT+01:00 Taylor Brandstetter
>     <deadbeef@google.com <mailto:deadbeef@google.com>>:
>     > saw that. Which means that individual documents are responsible
>     for defining
>     > how their extensions work with BUNDLE.
>     >
>     > But something still would need to define the general
>     restrictions for using
>     > "extmap" with BUNDLE, such as the ID restriction. Or is that
>     just something
>     > that's common sense and doesn't need to be specified?
>
>     https://tools.ietf.org/html/rfc5285#section-6
>     <https://tools.ietf.org/html/rfc5285#section-6> just mandates that the
>     IDs must be unique within a m= section, but at the end, all the WebRC
>     implementations use unique ID values across the entire SDP.
>
>     There are some RTP extensions, such as
>     http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01
>     <http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01>,
>     that work at *transport* level (rather than at m= section level), but
>     nothing prevents such a spec to work even if its ID is not unique
>     within the m= sections.
>
>     This is, IMHO we don't need a global behavior/requirement for the ID
>     values within bundled m= sections.
>
>
>     --
>     Iñaki Baz Castillo
>     <ibc@aliax.net <mailto:ibc@aliax.net>>
>
>
>
>
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