It is awesome Plasma allows automatic configuration for audio output, but the default setup isn’t robust enough to allow configuration in all situations. I think a few small front end and backend changes would improve things.
Right now a physical device is grouped together and sub-device output sources aren’t added to the simultaneous output grouping.
For example : GPU 1 has 5 ports.
2 HDMI and 3 DP
Currently the GUI has a line for this 1 GPU and any port that is actually plugged into the GPU shows up as a drop down. Then other physical devices such as an audio jack shows up as another device. If you activate the “Simultaneous” outputs check box it groups only GPU 1 and its active selection from above, but it doesn’t allow more sub-device selections.
What I propose is a simple GUI change.
You can leave it how it is for ease of use when not in “Simultaneous Mode” if desired, but when the user activates the Simultaneous checkbox it switches the listing to a per-audio source list.
So now GPU 1 with its 5 possible sources(if they are connected) would show up as 5 audio source outputs. Add 1 check box to say “combine this source” or whatever. Now when the user selects these sources it will be added to the virtual device and play the audio out of all those sources.
I don’t know the details of your audio hardware, but I suspect that it’s not possible to achieve what you are asking for.
The dropdown allows to chose between different device “profiles”, i.e. modes. The set of profiles and the behavior they give come from PulseAudio/the hardware, and only one profile can be active at any time
Maybe this pa config will help elaborate the point further. So I can manually configure this setup this way, but I cannot do this in the GUI. We need to break the drop down as shown in the picture below into different devices if in “simultaneous mode” and then maybe add a “checkbox” that allows this output source to be added to the “simultaneous mode” virtual device. This would make it much easier to configure.
