Tearing with opengl-hq and not with opengl on Gnome with MPV

Hello, I'm on Fedora 23 with Linux 4.4, Gnome Shell 3.18, MPV 0.17 and Nouveau driver (Nvidia GT430). In windowed mode I have tearing with opengl-hq and not with opengl. In fullscreen mode there is no tearing with both opengl-hq and opengl.

Here is the commands to test

mpv --no-config --vo=opengl-hq movie.mkv
mpv --no-config --vo=opengl movie.mkv

With Netrunner 14.2 (KDE - Kubuntu 14.04 derivative), MPV 0.17 and Nvidia proprietary drivers there is no tearing in windowed mode with opengl-hq. I tried Gnome Shell and Plasma 5 on Manjaro too. There is no tearing with Nouveau and Opengl-hq in windowed mode in Plasma 5 but there is stutter and there is tearing with Gnome Shell.

Actually there is dropped frames with Nouveau and Opengl-hq in windowed mode in all DE.

I opened an issue on MPV github and Wm4, the main MPV dev, said that my GPU (Nvidia GT430) with Nouveau driver is maybe too slow (no reclocking ?).

https://github.com/mpv-player/mpv/issues/2501

For me the logical behavior should be like on Plasma 5 with Nouveau, no tearing but if the GPU is not powerful enough the playback have stutter due to the dropped frames.

I contacted Rui Matos, a Mutter developper, and he advise me to file a bug here. Here is a summary of our talk to give all the infos I have :

Rui : Did you try gnome-shell on this environment (same as Plasma 5)? I supposed it'd still tear.

Me : I tried Plasma 5 and Gnome Shell on Manjaro with Nouveau on the same installation. The tearing was present in Gnome Shell but not on Plasma 5.

Rui : I'm afraid I can't help with this one, you'll have to file a nouveau bug.

Me: Can you confirm that even if the tearing was present in Gnome Shell but not on Plasma 5 on the same install I should file a bug to Nouveau.

Rui: Is kwin using opengl compositing? For the comparison to be meaningful you need to compare gnome-shell with kwin with opengl compositing enabled.

Me: I just checked to be sure and the opengl compositing is enabled for kwin too.

Rui: Ok. I still might be a driver issue that just happens to be triggered by different timings and API usage in mutter vs. kwin. Anyway, I can't really do much without the hardware to test, so it's still better to report it to nouveau.

Thank you !