No support for Audio Roles
Currently, audio in Plasma Mobile does not have any support for audio roles, so volume control is only for the output, which can be quite disconcerting when receiving notifications while listening to music in headphones for example.
Some quick investigation shows that the QtMultimedia plug-ins in 5.15 do not provide any audio roles support either, and supportedAudioRoles()
returns an empty list. In Ubuntu Touch, this is handled through the qtubuntu-media
plug-in, which directs media playback through media-hub
there, which sets the role on the GStreamer playbin used.
Current options seem to be patching of QtMultimedia 5.15 to provide and set roles on the streams in the gstreamer media plug-in, implement a new plug-in which does so, or to use the Ubuntu Touch plug-in and media-hub to handle media streams.