[pulseaudio-discuss] Receiving RTP streams with pulseaudio

[Rémi Denis-Courmont]

On Wed, 18 May 2011 10:40:48 +0100, Colin Guthrie <gmane at colin.guthr.ie>
wrote:
> If you have any recommendations for the defaults, please feel free to
> suggest them, but I guess the intention was to keep the traffic in house
> by default. We should likely expose via paprefs the ability to choose a
> public mutlicast group or something. WDYT?

There is almost everything you need to know in the already referenced RFC.

To summarize, the standard for SAP group address is:

 - 224.2.127.254 for global IPv4 multicast,

 - the last address in the netmask for non-global IPv4 multicast:
   SAP group = scope prefix | scope mask

 - ff0X::2:7ffe for IPv6 multicast where X is the multicast scope:
   SAP group = ff00::2:7ffe | (scope identifier << 120)

Link-local IPv4 multicast is 224.0.0.0/8, so the corresponding standard
SAP group is 224.0.0.255. VLC always selects the SAP group with the same
address family and scope as the advertized RTP multicast stream. This is
not required by the standard, but it only makes sense...

-- 
Rémi Denis-Courmont
http://www.remlab.net/