Am 26.01.2017 um 13:14 schrieb Mark Thompson:
On 26/01/17 11:00, Christian König wrote:
Hi Peter,
Am 25.01.2017 um 19:45 schrieb Peter Frühberger:
Peter, Rainer any idea what I'm missing here? Do you guys use some
modified ffmpeg for Kodi or how does that work for you?
do you set the format correctly, e.g.:
https://github.com/FernetMenta/kodi-agile/blob/master/xbmc/cores/VideoPlayer/DVDCodecs/Video/VAAPI.cpp#L2697
to create the surfaces?
Well the problem here is that the VA-API interface is not consistent and I'm
not sure how to implement it correctly.
See your code for example:
VASurfaceAttrib attribs[1], *attrib;
attrib = attribs;
attrib->flags = VA_SURFACE_ATTRIB_SETTABLE;
attrib->type = VASurfaceAttribPixelFormat;
attrib->value.type = VAGenericValueTypeInteger;
attrib->value.value.i = VA_FOURCC_NV12;
First Kodi specifies that NV12 should be used which implies that this is a 8bit
surface.
// create surfaces
VASurfaceID surfaces[32];
unsigned int format = VA_RT_FORMAT_YUV420;
if (m_config.profile == VAProfileHEVCMain10)
format = VA_RT_FORMAT_YUV420_10BPP;
But then Kodi requests a 10bit surface. Now what is the correct thing to do
here?
I can either create an NV12 surface, which would be 8bit but would result in
either an error message or only 8bit dithering during decode.
Or I can promote the surface to 10bit, which would result in a P010 or rather
P016 format.
Or and that is actually what I think would be best the VA-API driver should
trow an error indicating that the application requested something impossible.
I prefer the last. IMO that code is just wrong - you can't specify an 8-bit
format for a 10-bit surface. (I'm not really sure what it's trying to do, I
would have expected it to barf with the Intel driver as well, which doesn't
have any dithering support so Main10 video must be decoded to P010 surfaces.)
afterwards we just do drm / egl interop, via:
https://github.com/FernetMenta/kodi-agile/blob/master/xbmc/cores/VideoPlayer/DVDCodecs/Video/VAAPI.cpp#L1374
I'm not sure if that will ever work correctly. The problem is that VA-API leaks
to the application what the data layout in the surface is. As soon as we turn
on tilling that will only work with rather crude hacks.
I will try to get it working, but probably need help from you guys as well.
I don't think tiling should be relevant, but do correct me if this has more
issues than it does on Intel.
The problem here is I need to know what will be done with the surface
from the very beginning. E.g. if you want to scan it out directly to
hardware you need a different memory layout as when you just want to
sample from it.
Same applies to sampling from it from OpenGL and in this case also how
you want to sample from it etc etc...
To my mind, the PixelFormat attribute (fourcc) is only specifying the
appearance of the format from the point of view of the user. That is, what you
will get if you call vaDeriveImage() and then map the result.
And exactly that is completely nonsense. You CAN'T assume that the
decoding result is immediately accessible by the CPU.
So the only proper way of handling this is going the VDPAU design. You
create the surface without specifying any format, decode into it with
the decoder and then the application tells the driver what format it
wants to access it.
The driver then copies the data to CPU accessible memory and does the
conversion to the format desired by the application on the fly.
Tiling then doesn't cause any problems because it is a property of the DRM
object and mapping can automagically take it into account.
No it can't, tiled surfaces are not meant to be CPU accessible. So the
whole idea of mapping a surface doesn't make much sense to me.
Regards,
Christian.
With the Intel driver, when a surface is mapped to userspace it goes through
GTT and you see a linear layout; when a surface is mapped to some other
component (OpenGL or whatever) then the tiling information is available there
as a property of the object and can be handled appropriately (possibly by
throwing an error if it can't handle it, but hopefully it can).
Thanks,
- Mark
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