Re: [PATCH v6 00/12] Add VIRTIO sound card

[Volker Rümelin]

Am 21.08.23 um 08:10 schrieb Manos Pitsidianakis:
> Hello Volker,
>
> On Sun, 20 Aug 2023 14:46, Volker Rümelin <vr_qemu@t-online.de> wrote:
> > I tested the virtio-sound-pci device. It seems the device works 
> > unreliably. Audio playback has a lot of dropouts. I can actually hear 
> > my mouse moving around. Audio recording with audacity doesn't work. 
> > Either recording stops with an error or the recorded stream is silent.
> >
> > I'll see if I can change the code so audio playback works reliably. I 
> > don't think it makes sense to review the current code as it is. I 
> > will of course report any issues I find.
>
> have you been having this bad performance with pulseaudio/pipewire? 
> Are you using alsa for playback/recording in the guest?
>
> I am asking because this was my setup and I was wondering if it 
> affected the code I ended up with. For me I had normal playback, 
> except for a short delay at first (maybe something to do with alsa 
> buffer lengths, I am not familiar with ALSA much).
>
> If you can share your guest and host setup you used for this I can try 
> replicating it.

Hi Manos,

on the host I use pipewire. The audio device used for playback and 
recording is a Intel HDA device. I also tested recording from the 
playback monitor of the HDA device. The important command line arguments 
are: ./qemu-system-x86_64 -machine q35 -device 
virtio-vga-gl,xres=1280,yres=768,bus=pcie.0 -display 
gtk,zoom-to-fit=off,gl=on -machine pcspk-audiodev=audio0 -device 
virtio-sound-pci,bus=pcie.0,audiodev=audio0 -audiodev 
pipewire,out.frequency=48000,in.frequency=48000,id=audio0

The guest is Linux OpenSUSE 15.5 system. The guest uses PulseAudio. This 
means audacity ALSA audio recording was routed through PulseAudio. 
Audacity doesn't really start recording but after a few seconds it 
reports 'Wait timed out' and 'Error opening sound device. Try changing 
the audio host, recording device and the project sample rate'.

When I start QEMU with -audiodev 
pipewire,out.mixing-engine=off,in.mixing-engine=off,id=audio0 audacity 
only records silence.

For playback I use Rhythmbox or Audacity. If you don't immediately hear 
dropouts try activating and deactivating the QEMU gtk window in quick 
succession. A slightly increased processor load like moving the mouse 
around also increases the dropout rate.

With best regards,
Volker