[pulseaudio-tickets] [Bug 81824] New: audio from qemu guest suffers delay / pitch changes as of 5.x

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=81824

          Priority: medium
            Bug ID: 81824
                CC: lennart at poettering.net
          Assignee: pulseaudio-bugs at lists.freedesktop.org
           Summary: audio from qemu guest suffers delay / pitch changes as
                    of 5.x
        QA Contact: pulseaudio-bugs at lists.freedesktop.org
          Severity: major
    Classification: Unclassified
                OS: Linux (All)
          Reporter: dimitris at gmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: unspecified
         Component: clients
           Product: PulseAudio

I have a Fedora 20 guest running inside a Fedora 20 host, both using
pulseaudio.  Up until recently, I could use audio apps (mostly Skype) from
inside the guest without issues.

As of Fedora's rebasing of pulseaudio to 5.x, there seems to be some sort of
timing skew and delay.  This isn't limited to Skype; a slightly simpler test
case:

Running "paplay /usr/share/sounds/alsa/Front_Left.wav" repeatedly, I observe:

- In the host: no issues

- In the guest:

The clip's voice pitch sounds slightly lower.  This is consistent with running
the command under time(1), where the just over 1.5s clip consistently takes
50-60ms longer in reported real time to play in the guest.

Running the paplay command repeatedly in the guest, starting each new
invocation after the sound has stopped playing, there seems to be a "back up"
of audio stream building up.  After 5 or so runs, the sound doesn't start
playing until after the command has finished executing in the terminal. 
Waiting some time after that seems to exhaust whatever buffer is being emptied,
but the effect is back if I try another sequence of paplay commands.

The guest's configuration hasn't changed; as I mentioned above, this correlated
perfectly with the 4.x -> 5.x upgrade in Fedora.  More specifically, this
started happening when *only the host* was upgraded to 5.x, with the guest
still running PA 4.x.

The guest virtual hardware has always been:

00:04.0 Audio device: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family)
High Definition Audio Controller (rev 01)
0    alsa_card.pci-0000_00_04.0    module-alsa-card.c

The host has two devices available, with the problem present no matter which
one is used:

00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio
Controller (rev 03)
Bus 001 Device 010: ID 0d8c:0139 C-Media Electronics, Inc.
0    alsa_card.usb-C-Media_Electronics_Inc._DYNEX_USB_Audio_Device-00-Device   
module-alsa-card.c
1    alsa_card.pci-0000_00_1b.0    module-alsa-card.c

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