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Re: SDPng

From: Rob Lanphier <robla@real.com>
Date: Thu, 25 May 2000 18:13:53 -0700
Message-Id: <>
To: Markus Buchhorn <markus@acsys.anu.edu.au>, confctrl@ISI.EDU, atmsdp@eng.fore.com
Cc: www-smil@w3.org
Hi Markus,

(www-smil@w3.org added to the cc line.  See mail below for context)

The W3C SYMM Working Group is currently in the process of defining the next 
version of SMIL (Synchronized Multimedia Integration Language).  It's an 
XML-based language describing how to combine multimedia primitives (audio, 
video, images, text, etc) into a coherent presentation.

One of the proposed set of extensions to SMIL would be to add RTP delivery 
information into the SMIL specification.  The latest draft for this is 
located here:

A SMIL representation of SDP information would clearly be heavier than an 
SDP equivalent, but would also be a lot more expressive.  What's more, 
there's many cases where SMIL and SDP are both used in the same 
presentation today (RealPlayer and Quicktime support both).

I'll have to add the caveat that this particular portion of the spec hasn't 
received a lot of attention due to the fact that the bulk of the working 
group has more interest and/or expertise in matters higher in the 
application stack than getting the bits from point A to point B.  Input 
from this group on fleshing this proposal out would be greatly appreciated 
(best sent to www-smil@w3.org to keep me honest)  :)

Since the RTP portion of the SMIL Boston spec has such clear overlap with 
an existing IETF spec, it may make sense to separate this out and work on 
it as a namespace-separated extension to SMIL Boston, for which the details 
are sorted out in the IETF.  That would allow the group with the most 
interest and expertise in the matter to participate.



At 09:43 AM 5/25/00 +1000, Markus Buchhorn wrote:

>Hi All
>A quick question that leapt to mind from a couple of recent threads. I have
>seen mention of various extensions to SDP ("we're hitting some limitations
>of SDP"), some for application features (codecs, etc.), some for transport
>features (ATM leaps to mind, mobile users ?).
>Which group/who is looking at the next generation of SDP? (I think Mark
>Handley mentioned "some people call it SDPv2 and it's not really a v2"). I
>haven't seen any mailing lists under avt or mmusic (where it should be?)
>really discuss it.
>I'd be interested to see what is being done. One idea I wanted to canvas
>was the use of XML in session/content/transport description, with
>appropriate DTD's being created as necessary. Nicely extensible and
>pigeon-hole-able and container-able :-). However, it can be a bit heavy and
>SAP puts some strong recommendations on bandwidth usage and packet sizes.
>OTOH XML is compressible (e.g. wbxml) in special cases.
>Anyway - just wanted to lob a couple of cents in (around $US0.0114 at last
>glance...), and see what people are thinking.
>         Markus
>Markus Buchhorn,  Advanced Computational Systems CRC     | Ph: +61 2 62798810
>email: markus@acsys.anu.edu.au, snail: ACSys, RSISE Bldg,|Fax: +61 2 62798602
>Australian National University, Canberra 0200, Australia |Mobile: 0417 
Received on Thursday, 25 May 2000 21:10:26 UTC

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