[pulseaudio-tickets] [Bug 94763] New: ALSA module: tsched=0 causes skipping on nVidia HDMI output under QEMU-KVM

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94763

            Bug ID: 94763
           Summary: ALSA module: tsched=0 causes skipping on nVidia HDMI
                    output under QEMU-KVM
           Product: PulseAudio
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: pavucontrol
          Assignee: pulseaudio-bugs at lists.freedesktop.org
          Reporter: dan at danedgecumbe.com
        QA Contact: pulseaudio-bugs at lists.freedesktop.org
                CC: lennart at poettering.net

bool pa_alsa_may_tsched [modules/alsa/alsa-util.c] disables tsched if PA
determines that it is running within a VM.

This causes awful skipping audio on my system.
Removing the check enables the use of tsched and PA functions without a hitch.

Details
-------
Guest VM running under QEMU-KVM.
Arch Linux current 4.4.5-1-ARCH as of 2016/03/31
pulseaudio-git
commit 0f48b7c82378c32194b625d1fd886eee7f1e5928
Date:   Sun Mar 13 23:56:54 2016 +0200
NVIDIA proprietary driver on nVidia GeForce 960GTX - using nVidia HDMI audio.

git blame appears to stem from 2009 - has support for tsched improved since
then?

53b046d5 src/modules/alsa/alsa-util.c (Lennart Poettering   2009-11-05 03:23:08
+0100 1482)         /* We cannot depend on being woken up when we ask for in a
VM,
53b046d5 src/modules/alsa/alsa-util.c (Lennart Poettering   2009-11-05 03:23:08
+0100 1483)          * so let's fallback to classic IO based playback then. */

I would go ahead and submit a pull request to disable this check but I'm unsure
of the ramifications across different virtualization solutions.

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