All things related to multicast

[Toerless Eckert <>]

On Thu, Jun 06, 2002 at 10:23:40AM -0400, Bill Owens wrote:
> At 18:42 -0700 6/5/02, Toerless Eckert wrote:
> >Now you should certainly be able to use QuickTime to receive IP/TV
> >3.4 sourced MPEG4 streams, but of course the QuickTime 6.0 receiver
> >does not support SSM - unlike IP/TV 3.4, which does.
> 
> I use Quicktime 'wrapped' with MacTV, and I'd think that a similar 
> wrapper would be able to handle the SSM mechanics, wouldn't it? The 
> kernel would need IGMPv3, which MacOS doesn't yet have. But we can 
> hope. . . or build a patched kernel ourselves ;)

So, we tried to persuade Apple to support IGMPv3, but failed, i.e.:
Apple was not interested - i would guess that they simply didn't have
customers asking for IGMPv3/SSM support.

Now, we also tried to understand wether we could try to SSM enable
mac application via our IGMPv3lite mechanism and had to determine that
that is not possible because of quicktime. The same issue will apply
if you even have native IGMPv3 in the kernel - eg: With MacOX X, you
have a standard BSD kernel, so you could replace the IGMPv2 stack 
in that kernel with the IGMPv3 stack (from Wilbert de Graaf), but even
that would not help you to get a QuickTime application to become
SSM capable:

   The problem with QuickTime is that the API you have towards decoding
   a stream is too high-level: If you write an application that want's
   to use QuickTime (libraries) to decode an display a stream, then
   you have to call a high-level API, like NewMovieFromDataRef, which
   you basically pass a URL of type SDP and then the QuickTime library
   will internally get the SDP file, learn multicast group and
   IGMPv2 - join to the group.  And because there's also no access
   to the actual receive-socket onto which the IGMP join has to be
   executed, there's no way to trick around the fact that there's just
   an IGMPv2 done!

That's as much as i remember. I'd be happy to be proven wrong on this.

Cheers
        Toerless