Re: [Qemu-devel] What is the status of the QEMU sound rework?

[Markus Armbruster]

Copying Gerd...

Zir Blazer <address@hidden> writes:

> I'm a VGA Passthrough user that uses a QEMU VM to fully replace a Windows 
> native install as the main OS.
>
>
> Currently, one of the biggest hazzles for many users is that sound is hard to 
> get working properly with the emulated AC'97 and Intel HDA Sound Cards due to 
> crackle or latency issues (Latency issues heavily affects recording 
> scenarios, like voice chat applications in a VM). An example here, through 
> there are far more: 
> https://www.reddit.com/r/VFIO/comments/746t4h/getting_rid_of_audio_crackling_once_and_for_all/
>
>
> Some people managed to get sound working at acceptable levels by meddling 
> with the environmental variables, but most of the solutions come from a 
> trial-and-error esoteric procedure instead of structured troubleshooting, as 
> each user has to figure out which settings makes the emulated Sound Cards 
> work decently in his system. For those that failed getting the desired 
> results with emulation, they have to throw Hardware at the issue by using PCI 
> Passthrough of a Sound Card, or an USB Sound Card via USB Passthrough (Or 
> even have it plugged to an USB Controller passed to the VM via PCI 
> Passthrough), or using the passthroughed Video Card HDMI with a Monitor with 
> speakers, just to solve the sound issues. The problem is that this 
> complicates this type of setups a lot, and it makes impossible a typical use 
> case that would be that all the VMs output the sound to the host, which has 
> control of the Motherboard integrated Sound Card, and it mixes it to use a 
> single set of speakers for the entire system.
>
>
>
> I have been googling around and found that at several times, there were ideas 
> and proposal, and even some code, that were intended to overhaul QEMU sound 
> system. Examples includes:
>
> GSoC 2011 Xen PV Audio, a paravirtualized Sound Card 
> https://wiki.xenproject.org/wiki/Archived/GSoc_2011_Ideas
> GSoC 2015 QEMU rework of the sound environmental variables 
> https://wiki.qemu.org/Google_Summer_of_Code_2015#QEMU_audio_backend
> GSoC 2017 QEMU rework a patch series that did precisely that 
> https://wiki.qemu.org/Google_Summer_of_Code_2017#QEMU_audio_backend
> https://lists.nongnu.org/archive/html/qemu-devel/2016-01/msg02451.html
>
>
>
> Basically, what happened with all the previous ideas and proposals? Did any 
> of that work ever get into upstream QEMU?
> Is anyone tinkering with the idea of making a paravirtualized Sound Card and 
> its associated Drivers for the mainstream OSes to try to fix once and for all 
> the sound issues?