WebKitGTK cannot play video with hardware acceleration enabled
Epiphany, Eolie, etc. with WebkitGTK 2.34.1 cannot load video or get sound played well with a green-colored glitch graph.
command : "gsettings set org.gnome.Epiphany.web:/ hardware-acceleration-policy 'never'" or uninstall gstreamer-vaapi make Epiphany play video correctly.
OS is latest Arch linux, laptop with Intel integrated graphs and NVIDIA standalone, both xorg and wayland session, flatpak version also tested, the issue is same.
firefox performs normally with hardware acceleration.
Here are screenshot and logs by Vicente
I also tested earlier version of gstreamer-vaapi(1.16.x, 1.14.x from archlinux archive), though there's no strange graph and sometimes video get played well, most times video won't start. (and which plays well is always well, which cannot play will never play)