Subject: [AVT] I-D ACTION:draft-ietf-avt-rtp-toffset-02.txt

From: [email-masked]
Date: Thu, 19 Oct 2006 15:50:02 -0400

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

	Title		: Transmission Time offsets in RTP streams
	Author(s)	: H. Desineni, D. Singer
	Filename	: draft-ietf-avt-rtp-toffset-02.txt
	Pages		: 15
	Date		: 2006-10-19
	
This document describes a method to inform RTP clients when RTP
   packets are transmitted at a time other than their 'nominal'
   transmission time.  It also provides a mechanism to provide improved
   inter-arrival jitter reports from the clients, that take into account
   the reported transmission times.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-toffset-02.txt

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---

From: Dave Singer <[email-masked]>
Date: Fri, 20 Oct 2006 10:57:43 -0700

Hi folks

the only adjustment here from the previous drafts is to use URIs to 
identify header extensions, rather than reversed domain names.  URIs 
have the advantage that they might be de-referencable URLs, and 
indeed the draft now says that for RFCs, the extension name is the 
URL to the RFC.  So the following two now say that, as well.

I'm asking for last-call on these, as we've seen them a while, they 
are complete, and the discussion has died down.  Re-start the 
discussion if you disagree!

* * * *

This draft is a work item of the Audio/Video Transport Working Group 
of the IETF.

	Title		: A general mechanism for RTP Header Extensions
	Author(s)	: D. Singer
	Filename	: draft-ietf-avt-rtp-hdrext-06.txt
	Pages		: 17
	Date		: 2006-10-19

This document provides a general mechanism to use the header-
    extension feature of RTP (the Real Time Transport Protocol).  It
    provides the option to use a small number of small extensions in each
    RTP packet, where the universe of possible extensions is large and
    unregistered.  The actual extensions in use in a session are signaled
    in the setup information for that session.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-hdrext-06.txt

	Title		: Associating Time-codes with RTP streams
	Author(s)	: D. Singer
	Filename	: draft-ietf-avt-smpte-rtp-05.txt
	Pages		: 20
	Date		: 2006-10-19

This document describes a mechanism for associating time-codes, as
    defined by the Society of Motion Picture and Television Engineers
    (SMPTE), with media streams, in a way that is independent of the RTP
    payload format of the media stream itself.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-avt-smpte-rtp-05.txt

-- 
David Singer
Apple Computer/QuickTime

---

From: "Even, Roni" <[email-masked]>
Date: Sun, 22 Oct 2006 08:47:24 +0200

Hi,
My concern is with what looks to me like duplication between the header
extensions and the "shim" draft and I would like have one mechanism if
possible. 
Roni 

> -----Original Message-----
> From: Dave Singer [mailto:[email-masked]]
> Sent: Friday, October 20, 2006 7:58 PM
> To: [email-masked]
> Subject: [AVT] 3 to last-call - RTP header extensions
> 
> Hi folks
>

---

From: [email-masked]
Date: Sun, 22 Oct 2006 09:36:52 +0200 (CEST)

Hi Roni, folks,

Here's my take:

The shim draft's main intention/application is to signal certain
information (error resilience strength commands to be precise) from a
media decoder to a media encoder, utilizing the reverse direction media
path.  I won't comment on that idea in fear of using inappropriate
language, but I do have an opinion :-)

If work should contrinue at all on this draft (I'm personally not of the
opinion it should) I guess one avenue would be to split the draft into a)
transport of opaque bytes shimmed between RTP header and RTP payload, plus
related signaling, and b) the use case proposed (signaling of AMR encoder
operation points from an AMR decoder).  Then a) should be called a
profile.  That would be half-way clean, I think, though not necessarily
helpful, considering that the profile negotiation problem is (to the best
of my knowledge) still unsoved.

Dave's header extension stuff, on the other hand, is a comparatively clean
use of RTP's exstension mechanism that has been available for many years
(although perhaps intended more for experiments than for regular use).  It
should not break existing codebases and monitoring tools intended to
support any of the existing profiles, as long as the implementatiosn/tools
follow RFC3550 in throwing away extensions they don't understand.  Not
true for shim.  That's why shim should be called a profile.

Dave's stuff could carry the payload proposed in the shim draft, though at
a certain penalty of a few bytes per packet (using Dave's mechanisms, I
think it's 8 bytes penalty).  Some companies in 3GPP SA4 see this as a
major problem, as it makes radio optimization difficult.  Others disagree.
 But on the Internet, the 8 bytes should not do any significant harm.

I believe, the main discussion should be between Dave's header extensions
and the specification/use of new profiles.  I believe to recall that there
was a plan (proposed by Cullen?) to take this issue to the RAI area
mailing list, as it is closely related to profile negotiations.  But I
haven't seen any related traffic.

Regards,
Stephan

P.s.: in SA4, even the shim use case is by no means agreed.

---

From: Dave Singer <[email-masked]>
Date: Sun, 22 Oct 2006 21:48:55 +0800

>  But on the Internet, the 8 bytes should not do any significant harm.

The 8 bytes comes from the current treatment of the X bit (I have to 
have the signature and the length in there, even though my stuff is 
self-identifying and self-framing).  So they're not quite my fault. 
But they are there.

>haven't seen any related traffic.

Nor I.  I also note that we have been refining the header extensions 
for a while now, while the shim draft is both more recent (first 
version in august) and more specialized.  I guess I'd like their 
comment on why the general header extension is not appropriate, or 
other alignment issues.

-- 
David Singer
Apple Computer/QuickTime

---

From: "Desineni, Harikishan" <[email-masked]>
Date: Wed, 25 Oct 2006 09:57:43 -0700

Header extension is a profile independent approach. It is applicable to
RTP/AVP and all extensions of it (AVPF and others profiles). Whether a
particular profile is implemented or not, there is an easy way to make
use of header extension.

--Hari

> Sent: Sunday, October 22, 2006 6:49 AM
> To: [email-masked]; Even, Roni
> Cc: [email-masked]
> Subject: RE: [AVT] 3 to last-call - RTP header extensions
> 
> >(although perhaps intended more for experiments than for regular
use).
> It
> >Dave's stuff could carry the payload proposed in the shim draft,
though
> at
> >>>      provides the option to use a small number of small extensions
in
> >>  each
> >>>      RTP packet, where the universe of possible extensions is
large
> and
> >>>      (SMPTE), with media streams, in a way that is independent of
the
> >>  RTP