Sorry if you seem to know all the answers already, but I don't and so I have to
investigate.
Last year, I had literally worked this down to death. I followed every slightest
hint from countless searches, read through hundreds of discussions, driven
because I was unwilling to believe that up-/downloading of video textures with
D3D11 can't be done equally fast as with D3D9.
(the big picture was the implementation of D3D11 support for QuickSync where
the slowdown played a much bigger role than with D3D11VA decoders only).
Eventually I landed at some internal Nvidia presentation, some talks with MS
guys and some source code discussion deep inside a 3D game engine (not a
no-name). It really bugs me that I didn't properly note the references, but
from somewhere in between I was able to gather solid evidence about what
is legal to do and what Is not. Based on that, followed several iterations to
find the optimal way for doing the texture transfer. As I had implemented
D3D11 support for QuickSync, this got pretty complicated because with
a full transcoding pipeline, all parts (decoder, encoder and filters) can (and
usually will) request textures. Only the latest Intel Drivers can work with
array textures everywhere (e.g. VPP), so I also needed to add support for
non-array texture allocation. The patch you've seen is the result of weeks
of intensive work (a small but crucial part of it) - even when it may not
look like that.
Sorry if you seem to know all the answers already
Obviously, I don't know all the answers, but all the answers I have given
were correct. And when I didn't have an answer I always respectfully
said that your situation might be different.
And I didn't reply by implying that you would have done your work
by trial-and-error or most likely invalid assumptions or deductions.
I still don't know how you are actually operating this and thus I also cannot
tell what might or might not work in your case.
All I can tell is that the procedure that I have described (1-2-3-4) can
work rock-solid for multi-threaded DX11 texture transfer when it's done in
the same way as I've shown.
And believe it or not - I would still be happy when it would be
of any use for you...
Even though the discussion is heated (fitting with the weather here) I
don't mind. I learned some stuff and it pushed me to dig deeper. I can't
just accept your word for it. I need something solid if I'm going to
remove a lock that helped me so far.
So I'm currently tooling VLC to be able to bring the decoder to its
knees and find out what it can and cannot do safely. So far I can still
see decoding artifacts when I don't a lock, which would mean I still
need the mutex, for the reasons given in the previous mail.
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