[SR-Users] rtpengine alt stream question

[Alex Balashov]

Hello,

I recently encountered SDP attributes that look like this:

Media Attribute (a): alt:1 3 : njfxofkg bavpjfxg 192.168.2.59 41978
Media Attribute (a): alt:2 2 : fpukfyaj dqmiarjx 192.168.111.1 41978
Media Attribute (a): alt:3 1 : euvrwenk jctmhavh 192.168.238.1 41978

I was not familiar with these. However, RFC 4796 says:

alt: the media stream is taken from the alternative source. A
typical use case for this is an event where the ambient sound is
separated from the main sound. The alternative audio stream could
be, for example, the sound of a jungle. Another example is the
video of a conference room, while the main stream carries the
video of the speaker. This is similar to the 'live' role in
H.239.

RFC 6064 http://tools.ietf.org/html/rfc6064#section-4.4 speaks to this a
little as well.

This does not really make any clearer to me what these mean in this
scenario, and unfortunately I cannot find out from the user.

My question is: I assume that rtpengine (both Kamailio and daemon-side)
does not support this, correct? Are there any plans to in the future?
Can anyone with more experience with video, perhaps, give some insight
into the meaning and application of this attribute?

Thanks!

-- Alex