Re: [pve-devel] [PATCH docs] qm: update section about audio devices

[Stefan Reiter <s.reiter@proxmox.com>]

On 12/01/2021 14:39, Aaron Lauterer wrote:
> With the ability to configure the `none` backend, the audio section
> needs an update.
> 
> Signed-off-by: Aaron Lauterer <a.lauterer@proxmox.com>
> ---
>   qm.adoc | 17 ++++++++++++-----
>   1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/qm.adoc b/qm.adoc
> index 9c54903..d72798c 100644
> --- a/qm.adoc
> +++ b/qm.adoc
> @@ -796,11 +796,18 @@ Supported audio devices are:
>   * `intel-hda`: Intel HD Audio Controller, emulates ICH6
>   * `AC97`: Audio Codec '97, useful for older operating systems like Windows XP
>   
> -NOTE: The audio device works only in combination with SPICE. Remote protocols
> -like Microsoft's RDP have options to play sound. To use the physical audio
> -device of the host use device passthrough (see
> -xref:qm_pci_passthrough[PCI Passthrough] and
> -xref:qm_usb_passthrough[USB Passthrough]).
> +There are two backends available:
> +
> +* 'spice'
> +* 'none'
> +
> +The 'spice' backend can be used in combination with xref:qm_display[SPICE] while
> +the 'none' backend can be useful if an audio device is needed in the VM for some
> +software to work. To use the physical audio device of the host use device
> +passthrough (see xref:qm_pci_passthrough[PCI Passthrough] and
> +xref:qm_usb_passthrough[USB Passthrough]). Remote protocols like Microsoft’s RDP
> +have options to play sound.
> +

I know it wasn't added in this patch, but from personal experience, USB 
Passthrough for Audio will most likely give bad results. Even a pretty 
standard DAC at 16 bit stereo 48KHz results in bad crackling on my 
workstation. PCI Passthrough (of sound cards or USB controllers) works 
fine, as it omits going through user space (I suspect it's latency that 
kills it).

>   
>   [[qm_virtio_rng]]
>   VirtIO RNG
>