This plugin allows controlling the system value from a remote device. It works pretty well except for the following issues:
- if multiple audio sinks are available only the one returned by @DEFAULT_SINK@ can be controlled
- the remote device won't know if the user changes the volume in another way
While the first one can be easily fixed by adding a volume slider for each sink there is no easy fix for the second, because there is no commad like get-sink-volume in pactl. I already filed a bug about this https://bugs.freedesktop.org/show_bug.cgi?id=102998 . We either have to wait until this gets fixed (maybe I will write a patch myself) or use libpulse directly, which would our work more complex.
Though unfinished I'm showing it to get some early feedback. See corresponding Android patch