Writing modern volume control UIs (i.e. 'mixer tools') is much harder to get right than it might appear at first. Because that is the way it is I've put together a rough guide what to keep in mind when writing them for PulseAudio. Originally just intended to be a bit of help for the gnome-volume-control guys I believe this could be an interesting read for other people as well.

It touches a lot of topics: volumes in general, how to present them, what to present, base volumes, flat volumes, what to do about multichannel volumes, controlling clients, controlling cards, handling default devices, saving/restoring volumes/devices, sound event sliders, how to monitor PCM and more.

So make sure to give it at least a quick peek! If you plan to write a volume control for ncurses or KDE (hint, hint!) even more so, it's a must read.

Maybe this might also help illustrating why I think that abstracting volume control interfaces inside of abstraction layers such as Phonon or GStreamer is doomed to fail, and just not even worth the try.

And now, without further ado I give you 'Writing Volume Control UIs'.