[pulseaudio-discuss] Per-application volume glitching, and an idea for multiple channel volume control

[Jud Craft]

On a side note, that appears to be how Vista's per-app sound panel
works:  it doesn't detect apps, but sound streams.  Once a stream is
detected, the Vista mixer leaves that app's entry on the volume panel
even when the sound stops.

It does seem to monitor when the app closes though, and then removes
it from the panel.  But it definitely doesn't detect them until they
first play their sound.