VP9 encode support from Kaby Lake+

[EwoutH]

The Readme.md states VP9 encoding will only be supported from Ice Lake forward. The Readme and code over at intel/intel-vaapi-driver however states that VP9 encoding is supported from Kaby Lake forward.

So:

1. Is encoding VP9 with Kaby Lake possible?
2. Is encoding VP9 with Kaby Lake implemented in this repo?

[XinfengZhang]

@EwoutH , it is difficult to explain it. gen9 HW didn't implement all VP9 features, cant guarantee the quality and VP9 sub features enabling. another solution is hybrid solution( CPU & GPU work together to encode VP9) , but no much benefit comparing CPU solution.

[Brainiarc7]

@EwoutH ,

Case in point: VP9 encoding on KBL is limited to 60 fps only, as the MFX block on that H/W gen is incomplete as far as VP9 encoding is concerned.
This is the kind of stuff a company such as Intel wouldn't want to declare prod ready in mediasdk and the media-driver projects, considering the implications.