Subject: [Rmt] time-lined static media with FLUTE & IMG

From: [email-masked]
Date: Mon, 27 Oct 2003 12:51:53 +0200

Hi Magnus, Ross (and everyone)

1½-2 years back there was a draft on time-lined static media (draft-westerlund-avt-rtp-static-media-01) - basically to send files, text (etc) with timed presentation along with AV media streams. Since the basic requirements haven't gone away, but RMT has made progress on usable protocols, what do you think about using FLUTE (draft-ietf-rmt-flute-02) for the same job? With a quick comparison I think it should be pretty straight forward, although you may have some preferences (or extensions to the FLUTE-FDT) if you already have a working RTP-payload'ed implementation.

Ross mentioned sending ID-3 tags in-band with audio streams. Any ideas you have on doing this with FLUTE (ID3) and RTP (music) could be pretty useful for the Internet Media Guide (IMG) work in MMUSIC - how to move around (and announce) metadata for 'foo' multicast and unicast sessions.

Cheers, Rod.

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From: Magnus Westerlund <[email-masked]>
Date: Thu, 30 Oct 2003 11:00:27 +0100

Hi,

Sorry that it has taken some time to answer this mail. However I needed 
to do some reading. It is also interesting that I only received a single 
copy of this mail instead of the 4 that I should have received.

I will start to declare that I have not spent more time on this problem, 
and actually have dropped the RTP idea for this. The combination of 
binary objects with certain timing relations with continuos media is 
actual a hugh area, reaching into many areas.

I think that for a multicast session the usage of FLUTE to deliver the 
media works. As the transmission is unidirectional the sender can 
co-ordinate this with real-time media to ensure that bit-rate is used in 
a meaningful way. However I would like here to point out that the usage 
of congestion control or multi-layered transmission may be less useful. 
You still need to transmit the data so that the lowest bit-rate version 
has a good chance to reach the destinations. Having more layers would of 
possibly be able to increase the chance of delivery, however if you 
anyway has no congestion problem then there should be no problem of 
receiving the data with the single channel.

The larger problem as I see it is how to synchronize the time-lined 
static media objects with the continuos media. When I started looking at 
this problem we envisioned using SMIL. However this requires one to 
define a caching structure and having URI resolutions into that cache of 
objects. There are other scenarios where on needs to thing on how 
synchronize or bind data together.

What I understand of the RMT work is that you haven't really look into 
how to define session descriptions that actually work with any protocol 
instantiation.

But as conclusion, this topic needs a lot of further work. I think one 
needs to start looking at the requirements then see how the currently 
available protocols can be combined and where parts are missing.

Cheers

Magnus

-- 

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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