Subject: [AVTCORE] I-D Action: draft-ietf-avtcore-multi-media-rtp-session-01.txt

From: [email-masked]
Date: Mon, 22 Oct 2012 08:08:25 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
 This draft is a work item of the Audio/Video Transport Core Maintenance Working Group of the IETF.

	Title           : Multiple Media Types in an RTP Session
	Author(s)       : Magnus Westerlund
                          Colin Perkins
                          Jonathan Lennox
	Filename        : draft-ietf-avtcore-multi-media-rtp-session-01.txt
	Pages           : 19
	Date            : 2012-10-22

Abstract:
   This document specifies how an RTP session can contain media streams
   with media from multiple media types such as audio, video, and text.
   This has been restricted by the RTP Specification, and thus this
   document updates RFC 3550 and RFC 3551 to enable this behavior for
   applications that satisfy the applicability for using multiple media
   types in a single RTP session.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-avtcore-multi-media-rtp-session

There's also a htmlized version available at:
http://tools.ietf.org/html/draft-ietf-avtcore-multi-media-rtp-session-01

A diff from the previous version is available at:
http://www.ietf.org/rfcdiff?url2=draft-ietf-avtcore-multi-media-rtp-session-01

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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From: Magnus Westerlund <[email-masked]>
Date: Mon, 22 Oct 2012 17:14:14 +0200

WG,

(As author)

This updates makes three significant changes:

- Updates also RFC 3551
- Expandes on the RTCP bandwidth issues
   * Note solution is still an open issue
- Add a proposal for XOR based FEC handling in this context.

Cheers

Magnus

On 2012-10-22 17:08, [email-masked] wrote:
> _______________________________________________
> Audio/Video Transport Core Maintenance
> [email-masked]
> https://www.ietf.org/mailman/listinfo/avt
> 
> 

-- 

Magnus Westerlund

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Multimedia Technologies, Ericsson Research EAB/TVM
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From: Gunnar Hellström <[email-masked]>
Date: Tue, 23 Oct 2012 00:15:20 +0200

This looks good.

A couple of questions:

1. In 5.6, XOR-based FEC, it is said:
"unless the FEC data is carried in RTP Payload for Redundant Audio Data 
[RFC2198] which has another set of restrictions."
I assume that it is the restrictions described in section 7.2, last 
paragraph you mean. I suggest that you add that reference so that the 
sentence becomes:

" unless the FEC data is carried in RTP Payload for Redundant Audio Data 
[RFC2198] which has another set of restrictions described in section 7.2."

It also takes a bit of analyzing if the restrictions are valid for plain 
original use of RFC 2198 with simple redundancy of one codec payload 
type, or if it is just for the FEC data carried by RFC 2198 redundancy. 
( The "which" after RFC2198 can refer to either RFC2198 or the 
combination).  My deduction is that it is only the FEC-RFC2198 
combination that has restrictions.
I suggest that that is made more clear by further modification of the 
same sentence to become:

"unless the FEC data is carried in RTP Payload for Redundant Audio Data 
[RFC2198]. That case has another set of restrictions described in 
section 7.2."

2. This sentence in section 5.1 is very limiting for the usability of 
this draft:

"The second important consideration is that all media flows to be sent within a single RTP
  session need to have similar bandwidth."
It is further discussed in section 6.4.  
I have no hint on this. I just hope that you can find a good solution to release this limitation.  
Very few multimedia session have similar bandwidth requirements for video, audio and text.

/Gunnar