[Spice-devel] Help with solving a thread safety issue

nicolas prochazka prochazka.nicolas at gmail.com
Mon Sep 8 10:56:08 PDT 2014

I've done  differents tests, with the differents combinaisons between qemu
X and spice-server,
I can say  that is  since video adaptative streaming, the video streaming
is bad compare to the  old version (spice 0.12.3 / qemu 1.7 ).
When i set SPICE_DISABLE_ADAPTIVE_STREAMING=Y , my tests shows that's a lot
of frames are dropping, because of sound synchronisation, The only way to
get good streaming performance is to desactivate audio from client side. (

An other point, when you disable streaming detection from server side,
video is good, but the sound is very bad.


2014-09-08 16:57 GMT+02:00 Jeremy White <jwhite at codeweavers.com>:

> On Sat, Sep 06, 2014 at 08:59:47AM -0500, Jeremy White wrote:
>>>> I think there actually is the same issue when running within QEMU: sound
>>>>> is emitted from a QEMU thread:
>>>> Is there a bug or someone that is working on that issue?  I'd be
>>>> curious to
>>>> see if my patch resolves the problem for them.
>>> I've only noticed this through code inspection/gdb breakpoints after you
>>> pointed out the issue you found.  However, I'm fairly sure there has
>>> been reports on this mailing list of sound stopping after a while when
>>> watching a video. This matches very closely what you described.
>> I was thinking of
>> http://lists.freedesktop.org/archives/spice-devel/2014-July/017132.html
>> Maybe there was another email.
> I couldn't quickly figure out the threading arrangement in qemu, but if
> the main channel is being driven by a different thread than the audio
> channel, then I think this patch would have introduced a bug:
> ---
> commit bf9e210b21a66210b19f69fcaa4542b393b7dc22
> Author: Yonit Halperin <yhalperi at redhat.com>
> Date:   Fri Jan 25 09:34:19 2013 -0500
>     red_worker: video streams - adjust client playback latency
> --
> Of course, that's 18 months ago, so it seems to me we would have found it
> by now (despite it being a subtle, unpredictable bug that only occurs
> during video playback).
> But, just to be sure, Nicolas, would you mind setting the
> SPICE_DISABLE_ADAPTIVE_STREAMING environment variable prior to running
> the client and seeing if that changes anything?
> Cheers,
> Jeremy
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