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Re: [MMUSIC] IETF#89: BUNDLE: Q9: What are the criteria for allowing usage of the same PT value within multiple m- lines?

Christer Holmberg <christer.holmberg@ericsson.com> Mon, 03 March 2014 10:08 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Colin Perkins <csp@csperkins.org>
Thread-Topic: [MMUSIC] IETF#89: BUNDLE: Q9: What are the criteria for allowing usage of the same PT value within multiple m- lines?
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Date: Mon, 03 Mar 2014 10:08:19 +0000
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Subject: Re: [MMUSIC] IETF#89: BUNDLE: Q9: What are the criteria for allowing usage of the same PT value within multiple m- lines?
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Hi Colin,

We tried to define "codec configuration", but we never got text that people could agree to.

Personally I don't have any strong opinion which way we go (personally I am also ok forbidding re-usage of the same PT value). I just want to close the issue, and not once again "take it to the list".

Regards,

Christer

From: Colin Perkins [mailto:csp@csperkins.org]
Sent: 03 March 2014 11:34
To: Christer Holmberg
Cc: mmusic@ietf.org
Subject: Re: [MMUSIC] IETF#89: BUNDLE: Q9: What are the criteria for allowing usage of the same PT value within multiple m- lines?

Christer,

The bundled m= lines form a single RTP session. That means that they share a single RTP payload number space. The rule therefore has to be that you can only reuse the payload type across bundled m= lines if it refers to the exact same configuration of the exact same codec in all cases, where "exact same configuration" means that the a=fmtp: line and all other SDP attributes that configure the codec and packetisation of the media are identical.

If that's not specific enough, then MUST NOT reuse payload types across m= lines in a bundled group is the safe choice. I believe your propose that it's okay if you can handle the media is too vague, and will cause us problems down the line.

Colin




On 2 Mar 2014, at 08:44, Christer Holmberg <christer.holmberg@ericsson.com<mailto:christer.holmberg@ericsson.com>> wrote:
Hi,

One of the open issues we have in BUNDLE, is when it is allowed to use the same PT value within multiple m- lines.

We tried to come up with different criteria, including a "codec configuration" concept, but we never managed to agree on something.

So, in London, I intend to suggest that we simply say: if you offer the same PT value within multiple m- line, make sure you can handle the associated media when it arrives - period (keep in mind that you always indicate what you want to RECEIVE - the remote peer can still ask you to SEND using different PT values).

If you don't like this, please provide an alternative solution, because I want to close this issue in London. There is no idea to keep "taking the issue back to the list". We've done that for a few meetings already.

Regards,

Christer
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Colin Perkins
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