I can only comment on the Linux side of GPU accelerated video decoding as that's where my experience is: Pretty much _the_ standard for GPU accelerated video de

I can only comment on the Linux side of GPU accelerated video decoding as that's where my experience is: Pretty much _the_ standard for GPU accelerated video decoding is VDPAU, originally an nvidia project, now open source. Support for intel integrated GPUs came a little later in Linux under the guise of VAAPI (technically a subset of VDPAU). ATI/AMD also have a proprietary API called XVBA via their catalyst drivers but I haven't had much interaction with ATI hardware on Linux for a long time. VDPAU allows my 7 year old weedy 1.6ghz atom to play 1080p without breaking a sweat (around 2% CPU usage). VLC lagged behind a lot of other players (e.g mplayer, my personal favourite player; which added support in ~2009 or so), but has had decent VDPAU/VAAPI support since 2.1 (2013?). In the case of VDPAU on nvidia, support for 4K is a hardware limitation (the purevideo chip that actually does the decoding). It's supported on purevideo 5 and later (present on some later fermi and most Kepler architecture cards). It's the same story with Intel. Generally speaking, only Haswell and later architecture CPUs have support for 4K.