I’ve been using libvirt on my workstation to host a variety of local VMs for a while. Recently, Amazon Music HD became a thing. It’s pretty slick! OPUS and FLAC codecs! However, this is only supported on their desktop players and mobile players - not on the web player.
Well, I don’t run Windows, and despite my trying, the desktop app simply won’t run in Wine (or more specifically, Codeweaver’s Crossover). So hey, I have this Windows VM I use for the occasional Active Directory work and a non-administrative user on it… so I installed the player only to realize that, despite having an audio device defined in the libvirt domain, nothing was making it to my ears.
I wasted far too much time trying to use QEMU arguments to make it talk to pulseaudio via UNIX socket… when I discovered that SPICE actually supports audio passthrough! I already use SPICE for the GUI… and apparently the defaults are to pass audio through if SPICE is in use. Despite this, no audio was happening.
I ended up needing to add some stuff to the domain XML:
<sound model='ich9'>
<codec type='output'/>
<audio id='1'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x1b' function='0x0'/>
</sound>
<audio id='1' type='spice'>
<output mixingEngine='yes' fixedSettings='no'/>
</audio>
Note that I am using the output codec and only defining the output mixingEngine. Originally I tried to get the microphone working (with the ‘micro’ codec) but while it showed up, nothing seemed to make it into the VM. Since I don’t really need that, I just turned it off.
Just for reference, the rest of the SPICE settings are as follows.
<channel type='spicevmc'>
<target type='virtio' name='com.redhat.spice.0'/>
<address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>
<graphics type='spice' autoport='yes'>
<listen type='address'/>
<image compression='off'/>
</graphics>
<redirdev bus='usb' type='spicevmc'>
<address type='usb' bus='0' port='2'/>
</redirdev>
<redirdev bus='usb' type='spicevmc'>
<address type='usb' bus='0' port='3'/>
</redirdev>
I made sure to install the various drivers and the qemu guest agent via the virtio-win windows ISO.
I have since migrated to RHEL8, and when importing my KVM domains I ran into problems - specifically the <audio /> element is not available. I pulled my hear out for a while but found the solution was actually quite simple. All I had to do was remove the existing SPICE graphics, and re-add it. Upon doing so, I was left with a configuration like so and audio Just Worked. Note there is some device-specific video stuff in this as I have enabled OpenGL.
<graphics type='spice'>
<listen type='none'/>
<image compression='off'/>
<gl enable='yes' rendernode='/dev/dri/by-path/pci-0000:01:00.0-render'/>
</graphics>
<sound model='ich9'>
<alias name='sound0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x1b' function='0x0'/>
</sound>
<video>
<model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
<alias name='video0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
</video>
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