Re: [MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE allow/disallow PT sharing ??

Christer Holmberg <christer.holmberg@ericsson.com> Tue, 22 October 2013 08:02 UTC

From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Harald Alvestrand <hta@google.com>, Suhas Nandakumar <suhasietf@gmail.com>
Thread-Topic: BUNDLE/SDP : ISSUE#1: Should BUNDLE allow/disallow PT sharing ??
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Date: Tue, 22 Oct 2013 08:02:26 +0000
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Cc: Cullen Jennings <fluffy@cisco.com>, mmusic WG <mmusic@ietf.org>
Subject: Re: [MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE allow/disallow PT sharing ??
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Hi,

Please note the “DECISION (BERLIN-Q1/Q2/Q7): Usage of specific PT value for single codec configuration” thread, were Jonathan and Bo have presented some ideas for the PT-value-reuse criteria.

Regards,

Christer

From: Harald Alvestrand [mailto:hta@google.com]
Sent: 22. lokakuuta 2013 10:56
To: Suhas Nandakumar
Cc: mmusic WG; Christer Holmberg; Cullen Jennings
Subject: Re: BUNDLE/SDP : ISSUE#1: Should BUNDLE allow/disallow PT sharing ??

0: No, using PT 98 for both audio and video should absolutely not be allowed. Reuse of a PT for different codecs MUST NOT be done. I thought that was pretty clear in BUNDLE already; if it's not 100% crystal clear, it needs to be made clear.

1: Either the SDP should be rejected outright or the response to this SDP needs to disallow bundling those two lines. This belongs in the BUNDLE spec, and I thought it was pretty clear already.

2: If the question is about the "a=rtcp-fb" field, I think it should be classified as NORMAL. If it is about "a=rtcp-fb:98", it makes more sense to call it IDENTICAL.




On Tue, Oct 22, 2013 at 8:36 AM, Suhas Nandakumar <suhasietf@gmail.com<mailto:suhasietf@gmail.com>> wrote:
Hello All

   Section 5.2 in the draft-nandakumar-mmusic-sdp-mux-attributes-05 defines one category of OPEN ISSUE that was raised while analyzing multiplexing behavior of RFC4855, RFC5583 attributes for example.

As an example, let's consider the  SDP Example (copied from the draft)







// PTs are shared and have different feedback types

   a=group:BUNDLE audio video

   m=audio 3456 RTP/AVP 98

   a=mid:audio

   a=rtpmap:98 iLBC/8000

   a=rtcp-fb ack                  // Positive ACK

   m=video 3456 RTP/AVP 98

   a=mid:video

   a=rtpmap:98 VP8/90000

   a-rtcp-fb:98 nack rpsi        // Nack ACK

In the above case, PT 98 is repeated between the audio and video media lines. Audio media line has rtcp-fb ack and video media line has rtcp-fb nack.

Since RTCP reporting happens per RTP Session, we can see the following high level questions :

0. Should this be allowed ?

1. What should be the expected behavior in this scenario ?

2. What category assignment makes sense in here - IDENTICAL or NORMAL ??


Cheers
Suhas

[MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE allo… Suhas Nandakumar
Re: [MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE … Christer Holmberg
Re: [MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE … Christer Holmberg
Re: [MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE … Harald Alvestrand
Re: [MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE … Suhas Nandakumar
Re: [MMUSIC] BUNDLE/SDP : ISSUE#1: Should BUNDLE … Harald Alvestrand