In the past few months, Microsoft has done a lot of interesting development and operations, including open source mesa for windows subsystem for Linux (WSL) and supporting various Khronos APIs on Direct3D 12, so as to be used when there is a lack of local drivers on windows.
So far, this work has mainly focused on OpenGL, OpenCL and Vulkan, but Microsoft has even realized the support of Direct3D 12 video API in mesa and made use of the va-api status tracker support in mesa.
Simply put, this latest effort allows WSL GUI applications (such as media players) to enjoy hardware video acceleration. In the code incorporated into mesa 22.2 mainline, d3d12 video API has been implemented, and the relevant va-api entry has also been used for H.264 encoding / decoding. Therefore, linux video player / Multimedia software supporting video acceleration API (va-api) will be "magically" able to enjoy Direct3D 12 video acceleration when running in WSL (2).
This is for those who want to be in windows Subsystem for Linux is a great victory for users who get more powerful GUI software support, and further consolidate the dominant position of va-api as linux video API.
Although there is an experimental and independent va-api implementation on nvdec of NVIDIA, va-api does not support all GPU / drivers, so the support for Direct3D 12 video technically makes it more powerful on windows than Linux itself. Of course, at least for now, it is limited to H.264 codec, but the current code is designed to be scalable to support more video codecs.
Microsoft engineers have worked on the changes of d3d12 video support and gallium3d video acceleration front-end, and successfully tested the use of va-api with ffmpeg encoding / decoding / transcoding, Mplayer forked MPV and vaah264 under WSL with X11 window support. They may also support NVIDIA video decoding and UNIX presentation API (vdpau). As another supported implementation on d3d12 video, some changes of gallium3d vdpau are also taken as part of this merger, but the initial focus seems to be the va-api interface.