[Spice-devel] Gstreamer, RHEL 7, OpenGL and stripes

[Marc-André Lureau]

Hi

----- Original Message -----
> Hi,
>   yesterday/today I attempted to test the gstreamer patches.
> My approach was mainly as "user", install and see how does it work.
> 
> I installed Francois patches for spice-protocol and spice-server
> (not clients so I tested with mjpeg).
> The initial test was playing this video:
>   https://www.youtube.com/watch?v=IyTv_SR2uUo
> under Firefox on a RHEL 7 VM.
> The client window is maximized and the physical monitor resolution is
> 1920x1080.
> I started testing with gstreamer enabled or disabled during compile time.
> One thing I noted was that with gstreamer enabled the video have some
> strange effect where the video seems to go back and forth in different
> stripes! This was not happening without gstreamer enabled. Just video
> is updated a bit slowly and showing some horizontal stripes.
> 
> To try to debug another problem I wrote some code to blend some color
> to the different streams inside spice-server (you can have up to 50 streams)
> so I moved this debug code on top of Francois gstreamer patches.
> You can see code at
> https://cgit.freedesktop.org/~fziglio/spice-server/log/?h=stream_bug_francois
> (nothing fancy, just some ugly debug code).
> 
> What I discover was quite unexpected. The video is split in horizontal
> stripes
> of about (less than) 64K (65536) pixel so for instance the video I was
> playing
> was divided in stripes of 1671x39 pixels (about 23/24 stripes).
> Doing similar testing with RHEL 6 and vlc I realized that this behavior is
> common to OpenGL (using X11 output with VLC you have a big single stream).

This is a long-standing know issue with XPutImage splitting the draw in 64k requests. There is a patch for BIG-REQUEST support, but it's unlikely to go upstream afaik. Another attempt I had, at least for fixing gnome3 & llvmpipe, use XShm: https://lists.freedesktop.org/archives/mesa-dev/2015-June/085860.html 

Related bug: https://bugzilla.redhat.com/show_bug.cgi?id=1030024