Host is an ASUS Vivobook, Ryzen 7. Sound device on guest is set to ich9, also tried the ich6 option. which works equally well for sound output but still no mic. The AC97 option produces crackly sound so did not try that with the mic.
Virtual Machine Manager 4.10 powered by libvirt. Host and guests F37 Kernel 6.1.13-200 everything updated a few minutes ago.
Sound output works on guests. The webcam works after attaching the USB device.
Microphone works on the host. settings->input->input device, the vu meter bar bounces up and down with sound.
Guest settings->Input->Input Device says, Line In - built in Audio. The vu meter bar underneath shows no movement.
Discussions found elsewhere suggest that the mic works by default, so that is the expectation, i.e. that there are no other settings to be adjusted.
Have you made an usb redirector for your webcam. So that the webcam is visible if you start the guest os.
I could imagine so the system will recognize it.
The mic problem also appears for another user who also has an ASUS laptop, so I ordered a couple of usb headsets. Your post and another on the Internet suggests this. It is not a perfect workaround as a group of people can not sit in front of a laptop and all yell at it. But it will do for now.
Clearly, none of the USB devices listed for redirection is the built in mic.
I do not know how the built in mic is handled as an I/O device or if it is part of an IOMMU group. In some of the discussions people have talked about pass through of the entire sound device, which would work for our purposes - if that would solve the mic problem. I have to look into that another time. I was hoping that there was a neat explanation for the laptop built in mic …