Description
It would be nice to be able to raise and lower the volume directly in Emacs, not having to open Pavucontrols or equivalent to manually change the volume of the process. Not sure if it would be easy to come up with a solution portable between all the backends though, but for MPV it can be done with the --input-ipc-server flag and ncat. Example:
$ mpv --input-ipc-server=/tmp/eradiosocket ...
$ echo 'add volume -10' | ncat -U /tmp/eradiosocket
I suppose the functions would look something like
(defun eradio-lower-volume ()
(interactive)
(message (shell-command-to-string "echo 'add volume -10' | ncat -U /tmp/eradiosocket")))
except they would do something different depending on the backend.
An alternative solution which would probably work for most situations could be to ask the user for volume when executing eradio-play and pass that along as a command line argument when starting the player process. For MPV, there's the --volume flag. This solution would not allow changing the volume without restarting the player, but that's not all that bothersome, so it would still be very useful.