[Bug 766954] General stream error or black screen on Wayland

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=766954

--- Comment #15 from Egor Zaharov <nexfwall at gmail.com> ---
(In reply to Víctor Manuel Jáquez Leal from comment #14)
> Please note that in this case, libva loads the libva-xvba-driver. And it
> works in X.

Nope. This is my `r600_drv_video.so -> gallium_drv_video.so` symlink. This was
done to avoid problems, when programs trying to poke r600 driver for va and
does not find it. But later I've done LIBVA_DRIVER_NAME export using systemd
user.conf DefaultEnvironment. And forgot about it.

I don't know why in this particular case this ENV variable was not exported.
But it's still the same gallium driver.

And, I don't know what libva-xvba-driver is at all, because it does not exist
on Fedora.

> > So, VAAPI does not work at all in Wayland. 
> 
> Just to be exact (or nitpicking), libva supports Wayland, but the available
> drivers for your hardware do not.

Yep. I'm talking about driver, not the libva itself.

But also, later I found, what VAAPI is working on Wayland in mpv. But only of
you use "vaapi" video output (vo). I don't know what kind of "magic" it uses to
do that, but it was actually working. But forgot to save the output. If you
need it, I can try again.

> Yes, it is bad. That is why, in master, we already landed a patch which
> bails out the gstreamer-vaapi elements when the driver is not in a
> "white-list", and only the intel and gallium drivers are in that list (bug
> 764673).

And if driver is in white list, and fails to play video, Gstreamer will not try
to fall back to software decoding? Maybe I just misunderstood you (damn
language barrier), that is not what I meant.

I think gstreamer-vaapi can't be installed by default in distribution, only
because if it fails, then this is fatal. E.g. if this kind of hardware does not
have video decoding capatibilities, or just fails because of the driver, then
it can't play the video at all. But it should not be like that.

I think if it fails to play video using hardware acceleration, Gstreamer should
try to fall back to other plugin/sink which CAN play this codec. E.g. software
implementation. Just like mpv did it.

And then, the distributions can install it by default, without the fear what
user will get his Totem (or other gstreamer-based player) not playing videos.
Just a WARNING (output? dialog with "do not show this again" tick?) when it
can't do so using vaapi.

> mmmh... waylandsink needs the scaler extension and your setup doesn't
> provide it. I wonder why. But that is another issue.

This is Fedora 24, if you wonder. You can check why. But I don't understand
what is wrong.

> > Because, personally, only not working VAAPI holds me back from using Wayland
> > every day.
> 
> You can use the software decoders. But yeah, it would be much better if the
> drivers get in shape.

Software decoders can do it, but it will mean more CPU usage. And it feels like
I wasted it, because my hardware actually can decode it.

Hardware decoding saves CPU, so you can just leave your Firefox opened, while
you playing your favourite serial/anime in player. AMD E-350 is not beefy, it's
meant for low-cost machines and netbooks.

Also, Firefox can use gstreamer, so it kind of can use this plugin too.

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