Sorry: vo=opengl in combination with --hwdec=vaapi please
I also don't know if the mpv package you are using is some cripled debian / ubuntu version with patched out stuff. But you can easily try with the kodi package ubuntu ships. Turn on VAAPI and Prefer VAAPI Render-Method, that should make the issue clearly visible. Afterwards downgrade the kernel and see it working again.
Btw. using the CHV driver in combination with the very outdated vaapi 1.5.0 I don't consider a great choice either. CHV started to work "mostly bugfree" after libva / libva-driver-intel 1.6.1 was released.
Sorry: vo=opengl in combination with --hwdec=vaapi please
I also don't know if the mpv package you are using is some cripled debian / ubuntu version with patched out stuff. But you can easily try with the kodi package ubuntu ships. Turn on VAAPI and Prefer VAAPI Render-Method, that should make the issue clearly visible. Afterwards downgrade the kernel and see it working again.
Btw. using the CHV driver in combination with the very outdated vaapi 1.5.0 I don't consider a great choice either. CHV started to work "mostly bugfree" after libva / libva-driver-intel 1.6.1 was released.