All things related to multicast

[Frank Fulchiero <>]

On [Jul 24], at 6:21 PM, Greg Shepherd wrote:

> I don't think you should need a web browser to find a video stream.
> If the goal is an easy way for most viewers  to watch a video  
> channel, then the video player should show the available channels  
> automatically.

> Which video player?


What I envision does not exist yet in the multicast world  
(afaik)...except in a primitive form in VLC with SAP discovery.
Or in somewhat closed systems, like VBrick's. Not criticizing this  
approach, btw, sometimes you HAVE to control streams and clients, and  
VBrick is a good solution here.

Personally, I am more interested in promoting open programming over  
multicast, especially in educational and research environments.
I guess the closest that would come to what I envision is an open- 
source version of iTunes...combining discovery of media with the  
ability to play it.
With a good system for organizing many files and sources. Independent  
of web browsers, but can also interface to them.

A new multicast announcement/discovery open standard should also be  
independent of players, then their developers and manufacturers could  
decide whether to interface to it or not. That also brings up the  
question whether multicast streams should be treated any differently  
than unicast ones in discovery/announce systems.



> This follows the broadcast television model: turn on the TV, see  
> what's on, and then decide what to watch. You don't go to NTSC- 
> Google to find a channel, though that might be fine if it were  
> built into the television as a dedicated app. and integrated with  
> the television seamlessly.
>
>
> This works for TV because there is a national TV standard. With  
> streaming digital media, there are many standards to choose from. ;-)

Looking at the entire landscape, yes. But there do not appear to be  
that many standards in multicast streaming: UDP vs RTP for delivery.  
MPEG2 vs MPEG4 for encoding/decoding (granted, several parts, levels  
and profiles). SAP for announce/discovery.


> Yes, VLC does a great job on most content, but how much commercial  
> content uses it?

That is a good point. Richard Mavrogeanes probably scared them all  
off! ;-)
Sorry Richard, could not help myself...


> YouTube uses a browser quite successfully I gather. But it's no  
> less a proprietary solution than opening WMP to look for content..  
> or QT, or VLC, or Real.. But if a content directory service was  
> available via a web browser, then the SDP file would open the  
> correct player and all is well.

Yes, that is true. For some reason it seems more elegant to also have  
the programs show up in a player, like in iTunes.
Or, say the iPhone YouTube app. But open-source open-standard ones,  
that are not controlled by any one manufacturer.

A few other odd thoughts...

1. I think it's possible to hierarchically structure a long list of  
programs to make it more manageable. Good example here again is  iTunes.

2. There are interesting features in the SDP standard that could  
possibly be used in a new announce/discovery system. The  
a=cat:<category>  attribute "gives the dot-separated hierarchical  
category of the session." Not sure any clients use this...And then  
there is the fact that you can make up any attribute to extend SDP.  
For example, VLC uses “a=x-plgroup:Name” to group streams in one  
Program Group. Lots more could be done with the "a" categories. Well,  
just thinking out loud...

Finally, I am not pushing SAPs, just trying to best use them while  
waiting for something better to come along. Thanks for all your  
comments.

Frank Fulchiero
Digital Media Specialist
Connecticut College