I'm getting a new failure in d3d11 tests (with GL): `d3d11.c:36304: Test failed: Got hr 0x80004005`.
Oops, yes, I was not nearly careful enough with my testing. Fixed now.
Other than that it LGTM. Maybe NV12_D3D9 and NV12 would be another naming option to consider?
I don't hate it, although I'd reverse it and use NV12_D3D10 so that the other FOURCC formats remain consistent.
Not sure I like it better than NV12_PLANAR though, so I left it alone for now...