All things related to multicast

[Tom Pusateri <>]

On Nov 4, 2008, at 5:40 PM, Stig Venaas wrote:

> Frank Fulchiero wrote:
> > I think the challenge and goal should be a system that is flexible
> > enough to be used with hardware boxes, tuners, computer browsers,  
> > mobile
> > browsers, software players, etc.
>
> Yes
>
> > Not sure why you could not have the best of all worlds.
> > Besides the technical challenge of devising it, standardizing it, and
> > getting the content owners to use it!
>
> If done right, the channel reflector could work from hardware boxes,
> tuners or whatever. It's just a matter of using HTTP instead of SAP to
> retrieve the info. You may need some ways of quering just the relevant
> data and some way to filter hits, but I don't see any reason why it
> can't be done.
>
> My dream is to be able to search lots of metadata to find interesting
> content independently of (or not knowing) who is sending it etc. I  
> think
> the main problem with that though, is to get the content providers to
> provide the metadata. I'm not impressed with the info people provide  
> in
> SAP.
>
> Stig

A friend and I wrote a multicast guide a few years back that attempted  
to show available multicast streams on a web page. It listened to SAP  
and parsed the SDP announcements and tried to create the guide based  
on time information in the SDP file. It also allowed you to upload  
your SDP file for inclusion in the guide.

The problem we found was that there was hardly ever any start and stop  
times in the SDP files. So every stream showed up as available when  
more often than not, the content wasn't being sourced.

That was just an experiment at making a guide for people to register  
their content with and we used SAP to bootstrap it. SAP doesn't scale  
and we never intended to leave it based on SAP. My point is that the  
SDP files we came across were minimal at best. I would encourage  
people to spend a little extra time to get your SDP files to  
accurately reflect your content and transmission times.

Taking a step back though, this is a decentralized database  
synchronization problem complicated by access control requirements.

The client needs the SDP file and it can get it via HTTP, rsync, XMPP  
file transfer, email, or a variety of other methods creative people  
might thing of to replace SAP.

Tom