SUMMARY Today in OSes like Windows if you wish to listen to a recording device, it is a simple checkbox that you can enable. This results in you hearing any audio input from the recording device, whether that is a mic, line in or other device. In Linux in general, you need to add a loopback device using a command such as "pactl load-module module-loopback latency_msec=10". This is less than ideal for the average user who may not wish to have to manually delve into config files or run commands for this. If KDE could get a way to enable loopback quickly, it would be a quality of life improvement. Unsure if this is something KDE can do or if Pulse Audio needs to implement first? ADDITIONAL INFORMATION N/A
What's the use case for this? Is it to test your recording volume level?
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(In reply to Nate Graham from comment #1) > What's the use case for this? Is it to test your recording volume level? I see a few uses cases: 1. Testing recording volume as you mention 2. Input from another system, eg a classic game console with a capture card for video and loopback for audio. I personally use this to handle my work/person computers. My main PC (personal) is hooked to my DAC. My work Macbook is run to my main PC via TOSLINK input. I then run "pactl load-module module-loopback latency_msec=10" so that I can listen to my work Macbook through my main PC. I can then play videos/music on my personal PC while hearing notifications from my work Macbook.
I'm unsure if this is something KDE can own though? KDE would need to make assumptions for the underlying audio API or handle the various APIs available - does it do this already?
I think there's no reason why there couldn't be a button to allow users to easily set up loopback devices. One thing to note, however, is that this is specifically a limitation of PulseAudio. With PipeWire it's possible to directly link the toslink input port to the system output using tools such as qpwgraph (yes, it's a Qt5/Qt6 GUI from the same person who wrote qjackctl). With PW Plasma could directly do such linking, which has the benefit of avoiding the extra latency that loopbacks always cause. One slight difference to note is that loopback also applies volume control whereas direct linking will result in capturing at the full 100% volume. I'm a bit unsure about the exact effect but it would likely result in Mac OS playing back at whatever volume it's outputting to the toslink and any volume adjustments needing to be done there (although maybe I'm wrong?). As such in rare cases loopback might still be desired but it's definitely not required like it was with PulseAudio.