Quoting Hendrik Leppkes (2016-10-11 22:33:43)
> On Tue, Oct 11, 2016 at 9:34 PM, Anton Khirnov <an...@khirnov.net> wrote:
> > This format is used internally by the QSV encoder to store the encoded
> > bitstream.
> What does that even mean?
> It smells like some evil hackery going into the nice clean hwcontext.

Moderately evil.
If you want to use gpu surfaces with QSV, you need to supply a frame
allocator, which will be invoked to pass surface pools to it. For
encoding, this allocator gets invoked not only for the pool of input
frames, but also for a separate pool of (I assume) reconstructed frames
and another pool of MFX_FOURCC_P8, which on Windows needs to return
D3DFMT_P8 d3d surfaces. I think those are used to store the encoded
bitstream on the GPU.

In any case, while using P8 surfaces for this purpose is indeed rather
strange, there's nothing especially wrong about supporting them in the
DXVA2 hwcontext, it's just another surface format. The only hacky part
is the actual palette itself -- I didn't find a way to retrieve the
palette from a surface, so it's "emulated" by a dummy zero-filled
buffer. The actual contents are irrelevant for my specific use case (and
I don't expect it will be used for anything else).

Anton Khirnov
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