Re: URI Requirements

From: Warner ten Kate (tenkate@natlab.research.philips.com)
Date: Mon, Nov 23 1998


Message-Id: <36595950.E4636AF3@natlab.research.philips.com>
Date: Mon, 23 Nov 1998 13:47:12 +0100
From: Warner ten Kate <tenkate@natlab.research.philips.com>
To: "Davis, Rob - MTVN" <rob@mtvmail.com>
Cc: "'www-tv@w3.org'" <www-tv@w3.org>, "DASE E2E Team (E-mail)" <e-e@toocan.philabs.research.philips.com>
Subject: Re: URI Requirements

Davis, Rob - MTVN wrote:
> 

> Excuse me for jumping in midstream. I hope you all find my comments useful.
> I've been lurking for awhile and figured it is time to add a broadcaster's
> point of view. I work with convergence projects at MTV Networks. Of course,

Thanks for your comments. I found them quite useful. 
Sorry for responding a little delayed. 

I am not sure whether in our current requirements document 
we have touched the proper requirements to fulfill the needs 
you describe. Maybe a little discussion can bring us further. 
Below I suggest an improvement in the requirements list.


> Of course, the EPG doesn't tell you the one thing everyone will need to
> know, which is "When is the commercial break?" The reality of the TV
> business world is that some resources we send during content may not be
> appropriate for use during commercials, and some commercials may require
> their own resources. Therefore, whatever system we use for resource ID must
> also consider the commercials as "segments."

You confuse me. This sounds like a contradiction.

I always understood that content providers wanted:
A: don't provide a mechanism to indicate the commercials
   (such that they can be skipped), the so-called 
   commercial killer.

I understand the above as:
B: do provide a mechanism to indicate commercial breaks
   (such that resources can be retrieved).


(Btw. DVB-SI provides a lite mechanism to signal commercial 
breaks; it is an optional feature, though. It is not used 
as far as I am aware, because of reason A above.)


> 
> What is comes down to is that all broadcasters need a direct an accurate
> connection between on-air and the resources being sent. Right now that data
> exists at the head-end in real time.

This is not an URI requirement, 
but a transport system/protocol requirement.

You can use DSM-CC to solve that. You need an application document 
to express how the various resources (media) are composed together, 
eg. HTML. In your case the program application is interrupted with 
a commercial application (another HTML page), each using different 
resources, modeled in DSM-CC as separate namespaces. 

DSM-CC also provides the accurate timing you need. DSM-CC provides 
a so-called NPT (Normal Playing Time) which locks to the system 
clock of 27 MHz. You can trigger resources with that accuracy.
I suppose that fulfills your need (I don't know the accuracy of 
the LMS):
> 
> If we really want to solve the problem, we would develop a system that puts
> a continuous trigger signal in the video feed so that we can ID at any time
> exactly what is on, where we are in it, and so forth.
> 
> Without that, the LMS is as good as it gets.



The URIs are declared in the application document (HTML page). 
They should point in the corresponding namespace, which is existing 
for at least the time period the commercial is up. 


The precise synchronization in presenting your resources is 
expressed in the application document (HTML), not in the URI. 
The application listens to the events from your transport stream 
and synchronizes the presentation of the resource, indentified 
by the URI, in relation to that event. (So, with DSM-CC you 
have 27 MHz accuracy.)

The URI should only indicate that the resource is available 
in the channel. It is up to the service provider to take care 
that the resource and the application calling the resource are 
scheduled in proper synchronization. (You need your LMS for that.)

--

If information from the commercial stays longer in the 
transmission channel than the application, I would model that 
as a data broadcasting service, having its own channel/service ID, 
not that of the regular program.
[I am not sure whether the term 'data broadcasting' has the same
interpretation in EU and USA. In EU we think of a stand-alone 
service, providing data to (subscribed) users. The receiver is 
not a TV per se. Pushing Web-pages is an example, stock quotes 
another.]


--

Triggered by your comment I changed the fourth requirement. 
I hope that reflects your needs.

o  Given a URI, it must be possible for a receiver to determine 
   the time period(s) within which the resource can be retrieved 
   from the (also resolved) location. The accuracy of the time 
   period should correspond with the event's granularity as 
   provided by the service signaling system.
   [Note: the time period in which the resource is valid/meaningful 
    is controlled by the lifecycle of the application calling the 
    resource. That application also controls the synchronization 
    of the time period in which the resource is presented. The URI 
    indicates the time period within which the resource is available.]


Warner ten Kate.

--
Philips Research Labs. WY21 ++ New Media Systems & Applications
Prof. Holstlaan 4 ++ 5656 AA  Eindhoven ++ The Netherlands
Phone: +31 4027 44830
Fax:   +31 4027 44648    tenkate@natlab.research.philips.com