[asterisk-users] One leg in a conference and adjusting stream volume of other leg

[Markus]

Hi all,

I'm looking for some serious help. :)  I couldn't find a better 
description for my problem... I think it is quite complex! Here's what I 
would like to achieve:

A SIP caller dials into to my Asterisk 10. He will automatically listen 
to a specific MP3 stream.

Other SIP callers dial also into my Asterisk. They all will 
automatically listen to the same MP3 stream.

All callers automatically are joined into the same conference and are 
able to speak/hear each other at the same time they're listening to the 
stream.

The tricky part:

A caller may now press some digits on their their keypad, like 1, or 2, 
and this will have the effect that the volume of the stream is 
increasing or decreasing.

BUT:

When they adjust the volume of the stream, if effects only their stream, 
and not the volume of the stream of the other callers.

In short: All callers at all times are *always* in the same conference, 
but each caller is able to increase or decrease the volume of "their" 
MP3 stream individually.

If I'm right the MP3 stream cannot come from inside conference (MeetMe 
or ConfBridge with MOH) because there is no functionality to control the 
volume individually. So, I guess the basic foundation is a plain 
conference room without MOH, and then somehow the MP3 stream is "joined" 
to each caller individually, without bridging the audio into the whole 
conference ...

I don't know where to start. Queue? Local channel? ...

Thank you so much for any advise! I'm puzzled. :)

Regards
Markus