Video playback slows, loses sound intermittently in Artix guest

[HarryMan]

When playing a video on Artix linux in either Firefox or Qupzilla, at some point the video slows down and the sound disappears completely. I find there are only a few ways to get the sound back: 1) stop the playback momentarily and then restart it; 2) move the current place in the playback to a few moments prior and play from there; 3) re-load the page and restart the playback; 4) reboot the VM (soft reboot works).

The first 3 methods are unreliable. By "soft reboot" I mean as opposed to shutdown and restart of the VM session, analogous to a warm boot.

I recall seeing a number of "buffer underrun" messages somewhere when I first investigated this weeks ago, but now I don't remember which logs. I am seeing lots of messages that look like "VMMDev: Guest Log: VGDrvCommonIoCtl: Unknown request iFunction=..." in the syslog and messages logs.

Host is CentOS 6.9 (which is using kernel 2.6.32), running VBox 5.1.32 with extensions on AMD Phenom II X6 and 12GB memory.

Guest is Artix (kernel 4.9.75) -- Arch Linux variant with systemd removed, replaced by openrc. Guest is configured with 2D/3D disabled. KVM paravirtualization. 1.5GB and 2 vcpu's. (The 2nd vcpu was added in hopes of fixing the problem. It didn't.) Desktop is LXQt. This is the system that has the playback problem, just to re-iterate.

Another guest happens to be Devuan (kernel 3.16.0) -- Debian variant with systemd removed, replaced by (IIRC) sysV init and (IIRC) runit or something. No 2D/3D either. 3GB memory and 1 vcpu. Desktop is XFCE. The playback issue does not happen on Devuan. This is included as an analog for comparison.

Pulseaudio has been removed on all guests and the host. Note that both VMs included in this report do not run systemd. Both are using ALSA audio driver with AC97. Both VMs are 64 bit systems.

Because I am only experiencing the video playback problem on Artix, I am assuming the problem is related to something unique to that distro. Logs from sessions where I tried to playback the same exact video are attached to this report.

[HarryMan]

I rebuilt the GAs from the ISO -- these work better than the GAs distributed with Artix, which are btw 5.2, not 5.1.

OK, what are the ramifications for this? What sort of malfunction or dysfunction should I expect? This has been running for a day or more now without incident so far.

[socratis]

OK, I'll give it a shot. The audio/video problems are an ongoing (uphill) battle. Just take a look at the bug tracker and search for audio and/or video. Be sure to include the closed duplicates.

For example I had never had satisfactory sound output (or some times not at all) on my OSX guests, until the very latest test builds. That is if the VM didn't crash when you were trying to configure the sound input/output. And I'm not talking about an online video, I'm talking about the "beep" sound...

So, with that in mind, I would try (and keep on trying) the latest test builds. The generic ".run" should be fine for your host. As for your Guest Additions (GAs), they have nothing to do with your sound output, neither with your video. The best they could help you with are 3D acceleration, not needed in your case. But if they run fine, hey, who am I to say "dump them"...

[HarryMan]

Those error messages about the missing functions seemed to be mucking with the system. What if it was interfering with the operation of the system, particularly in terms of timing? As I understand it, to get accurate and clear sound playback depends a lot on timing. If the mismatched GAs were somehow interfering with the timekeeping, it might explain the sound issue, and maybe video also.

At any rate, since I started running with the re-built GAs from the VirtualBox ISO, I've not noticed any sound or video issues. I'll continue to post, however. I've noticed in the past that these issues (sound and video playback problems) can be, and often are, intermittent and variant.

[HarryMan]

It may be related to running pysol while video is running, or maybe just pysol period. Last night, I found my entire VM had frozen and syslog-ng had not logged any messages for almost 24 hours. Video was not even running -- it had been stopped, but pysol was left running at the end of the last game played.

I have been noticing, over many months, that pysol is highly suspect. I will post more as I find out more.

[HarryMan]

Problem seems to have abated. Not sure what changed that made the problem disappear, but it is gone now.