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

[Markus Armbruster <armbru@redhat.com>]

Copying Gerd...

Zir Blazer <zir_blazer@hotmail.com> writes:

> I'm a VGA Passthrough user that uses a QEMU VM to fully replace a Windows native install as the main OS.
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> 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/
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> 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.
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> 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:
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> 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
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> 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?