Bug#1021032: vlc: playing videos results in a black screen

[Dirk Griesbach]

Am Mo, 07. Nov 2022 um 00:11:41 +0100 schrieb Alexis Murzeau:
I'm jumping in to add information, I also get black screen issue after 
updating Qt from 5.15.4 to 5.15.6.


I also get graphical issues in the playlist, when resizing the VLC 
window. These graphical issues appear also in virtualbox-qt.


I've already created a bug on qt: #1023580
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1023580


Thanks! That one was fixed in Qt 5.15.6+dfsg-4 and since then video 
output in vlc is working again for me.


Best regards,
Dirk

Bug#1021032: vlc: playing videos results in a black screen

[Alexis Murzeau]

Hi,

On Sat, 08 Oct 2022 14:30:43 +0300 =?ISO-8859-1?Q?R=E9mi?= Denis-Courmont 
 wrote:

Le lauantaina 8. lokakuuta 2022, 12.40.56 EEST KeyofBlueS a écrit :
> Hi all. Let's continue here from #1021140
> 
> 
> It seems this issue it's not completely fixed. Before it was always

> reproducible under any circumstance, when now there are at least two ways
> to always trigger it:

I believe that the issue is not fixed at all.

The symptoms started showing up after Debian updated Qt, and affect only the Qt 
GUI. The last attempt to fix it affected the VA-API video decoding path in such 
a way that it will still *fail* at a different pace than it did before the fix. 
Then it will fallback to VDPAU or to software decoding path.


[...]


I'm jumping in to add information, I also get black screen issue after updating 
Qt from 5.15.4 to 5.15.6.

I also get graphical issues in the playlist, when resizing the VLC window. 
These graphical issues appear also in virtualbox-qt.

I've already created a bug on qt: #1023580
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1023580

--
Alexis Murzeau
PGP: B7E6 0EBB 9293 7B06 BDBC  2787 E7BD 1904 F480 937F

Bug#1021032: vlc: playing videos results in a black screen

[Rémi Denis-Courmont]

Le 8 octobre 2022 16:40:49 GMT+03:00, KeyofBlueS  a écrit 
:
>> It would be interesting to see if it reproduces with VLC <= 3.0.12 and >=
>> 3.0.18~rc1. (...)
>> It could also be something else. I don't pretend to know that.

>I've compiled 3.0.18-rc2 (sorry i wasn't able to build 3.0.12 also), sadly
>it is still reproducible. I really hope that if it's unfixable, at least
>some workaround could take place, i'm not ready to switch to wayland.

In that case, my hypothesis about the X11 protocol problem is invalidated. 
Updating to 3.0.18 won't fix anything and there are no fixes to backport, and 
no (known) patches to revert either.

Note that VLC 3.0 doesn't support Wayland properly anyway. That would require 
VLC 4.0 which is still far from ready for prime time.

Thanks for the testing.

Bug#1021032: vlc: playing videos results in a black screen

[Aaron]

VAAPI works nicely now under wayland, but users need to export 
LIBVA_DRIVER_NAME=
Cheers.
Aaron.

libva info: VA-API version 1.15.0
libva info: User environment variable requested driver 'radeonsi'
libva info: Trying to open 
/usr/lib/x86_64-linux-gnu/dri/radeonsi_drv_video.solibva info: Found init 
function __vaDriverInit_1_15

Sent with [Proton Mail](https://proton.me/) secure email.ukbeast@debian:~$ LIBVA_DRIVER_NAME=radeonsi  vlc -v
VLC media player 3.0.17.4 Vetinari (revision 3.0.13-8-g41878ff4f2)
[5562c0571580] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
Warning: Ignoring XDG_SESSION_TYPE=wayland on Gnome. Use QT_QPA_PLATFORM=wayland to run on Wayland anyway.
[5562c06128b0] main playlist: playlist is empty
[7f4f2c004910] gl gl: Initialized libplacebo v4.208.0 (API v208)
libva info: VA-API version 1.15.0
libva info: User environment variable requested driver 'radeonsi'
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/radeonsi_drv_video.so
libva info: Found init function __vaDriverInit_1_15
libva info: va_openDriver() returns 0
[7f4f2c243170] gl gl: Initialized libplacebo v4.208.0 (API v208)
[5562c06438e0] pulse audio output warning: starting late (-4066 us)
[7f4f34189f50] qt window warning: orphaned video window
QObject::~QObject: Timers cannot be stopped from another thread

Bug#1021032: vlc: playing videos results in a black screen

[KeyofBlueS]

On Sat, 8 Oct 2022 15:40:49 +0200 KeyofBlueS  wrote:
> On Sat, 08 Oct 2022 14:30:43 +0300 =?ISO-8859-1?Q?R=E9mi?= Denis-Courmont
<
> r...@remlab.net> wrote:
>
> > I believe that the issue is not fixed at all.
> >
> > The symptoms started showing up after Debian updated Qt, and affect only
> the Qt
> > GUI. The last attempt to fix it affected the VA-API video decoding path
> in such
> > a way that it will still *fail* at a different pace than it did before
> the fix.
> > Then it will fallback to VDPAU or to software decoding path.
> >
> > But it will still fail anyhow, and the exact same failure occurs when
> playing
> > video outside the VLC GUI, which is unaffected. Therefore, I am led to
> believe
> > that this is a race condition that became apparent with the Debian Qt
> update,
> > and partially worked around by the last VA change in the Debian VLC
> packaging.
> >
> >
> > It would be interesting to see if it reproduces with VLC <= 3.0.12 and
>=
> > 3.0.18~rc1. If not, then the X11 protocol-level race condition with
> parenting
> > the VLC video window would be the obvious culprit. Unfortunately though,
> I
> > reckon that that is in fact an X11 protocol design issue that is
> unfixable
> > (short of switching to Wayland, basically), though there are potential
> > workarounds.
> >
> > It could also be something else. I don't pretend to know that.
> >
> > --
> > レミ・デニ-クールモン
> > http://www.remlab.net/
>
> I've compiled 3.0.18-rc2 (sorry i wasn't able to build 3.0.12 also), sadly
> it is still reproducible. I really hope that if it's unfixable, at least
> some workaround could take place, i'm not ready to switch to wayland.
>
> Regards.

Don't know if it can be relevant, but vlc 4.0.0-dev in master, both with
classic and modern layout, doesn't suffer from this issue, or at least i'm
not able to reproduce it.

Bug#1021032: vlc: playing videos results in a black screen

[KeyofBlueS]

On Sat, 08 Oct 2022 14:30:43 +0300 =?ISO-8859-1?Q?R=E9mi?= Denis-Courmont <
r...@remlab.net> wrote:

> I believe that the issue is not fixed at all.
>
> The symptoms started showing up after Debian updated Qt, and affect only
the Qt
> GUI. The last attempt to fix it affected the VA-API video decoding path
in such
> a way that it will still *fail* at a different pace than it did before
the fix.
> Then it will fallback to VDPAU or to software decoding path.
>
> But it will still fail anyhow, and the exact same failure occurs when
playing
> video outside the VLC GUI, which is unaffected. Therefore, I am led to
believe
> that this is a race condition that became apparent with the Debian Qt
update,
> and partially worked around by the last VA change in the Debian VLC
packaging.
>
>
> It would be interesting to see if it reproduces with VLC <= 3.0.12 and >=
> 3.0.18~rc1. If not, then the X11 protocol-level race condition with
parenting
> the VLC video window would be the obvious culprit. Unfortunately though,
I
> reckon that that is in fact an X11 protocol design issue that is
unfixable
> (short of switching to Wayland, basically), though there are potential
> workarounds.
>
> It could also be something else. I don't pretend to know that.
>
> --
> レミ・デニ-クールモン
> http://www.remlab.net/

I've compiled 3.0.18-rc2 (sorry i wasn't able to build 3.0.12 also), sadly
it is still reproducible. I really hope that if it's unfixable, at least
some workaround could take place, i'm not ready to switch to wayland.

Regards.

Bug#1021032: vlc: playing videos results in a black screen

[Rémi Denis-Courmont]

Le lauantaina 8. lokakuuta 2022, 12.40.56 EEST KeyofBlueS a écrit :
> Hi all. Let's continue here from #1021140
> 
> 
> It seems this issue it's not completely fixed. Before it was always
> reproducible under any circumstance, when now there are at least two ways
> to always trigger it:

I believe that the issue is not fixed at all.

The symptoms started showing up after Debian updated Qt, and affect only the Qt 
GUI. The last attempt to fix it affected the VA-API video decoding path in such 
a way that it will still *fail* at a different pace than it did before the fix. 
Then it will fallback to VDPAU or to software decoding path.

But it will still fail anyhow, and the exact same failure occurs when playing 
video outside the VLC GUI, which is unaffected. Therefore, I am led to believe 
that this is a race condition that became apparent with the Debian Qt update, 
and partially worked around by the last VA change in the Debian VLC packaging.


It would be interesting to see if it reproduces with VLC <= 3.0.12 and >= 
3.0.18~rc1. If not, then the X11 protocol-level race condition with parenting 
the VLC video window would be the obvious culprit. Unfortunately though, I 
reckon that that is in fact an X11 protocol design issue that is unfixable 
(short of switching to Wayland, basically), though there are potential 
workarounds.

It could also be something else. I don't pretend to know that.

-- 
レミ・デニ-クールモン
http://www.remlab.net/