Hi Rainer,
the render thread doesn't wait either.
See when you dispatch some work the AMD drivers always wait for
prerequisites in the background, not in the foreground.
The older radeon driver uses hardware semaphores for this while amdgpu
has a GPU scheduler which handles that stuff.
This is very important because when you hold back rendering work in the
application the driver stack won't know about it and power management
starts to stutter.
Not so important for 1920p because power management should be able to
compensate the work peaks, but for 4K that's something mandatory to let
the driver be able to estimate future load.
We even discussed in our multimedia meeting if we shouldn't limit 3D
power management when UVD/VCN decoding is active because of that
problem. But I'm not very keen about those workarounds because it's
really counterproductive for transcode use cases to have the 3D engine
idling around with high clocks.
Regards,
Christian.
Am 11.02.2018 um 12:51 schrieb rainer.hochec...@onlinehome.de:
Hi Christian,
For Kodi it is better to wait on the thread that does decoding than later
by the render thread. Means it is desired to call it.
Does vaSyncSurface block as stated by the docs?
Regards,
Rainer
*Gesendet:* Sonntag, 11. Februar 2018 um 11:02 Uhr
*Von:* "Christian König" <christian.koe...@amd.com>
*An:* "Philipp Kerling" <pkerl...@casix.org>, s...@jkqxz.net
*Cc:* rainer.hochec...@onlinehome.de, peter.fruehber...@gmail.com,
mic...@daenzer.net, mesa-dev@lists.freedesktop.org,
harry.wentl...@amd.com, lru...@libreelec.tv
*Betreff:* Re: [Mesa-dev] 10bit HEVC decoding for RadeonSI v2
Am 09.02.2018 um 21:35 schrieb Philipp Kerling:
> Hi,
>
> resurrecting this thread again since there's been some progress on the
> Kodi side.
>
>> For the EGL part, see <https://github.com/01org/libva/pull/125>
>> and
<https://lists.freedesktop.org/archives/mesa-dev/2017-October/171246.html>.
> We recently started testing vaExportSurfaceHandle support, so we will
> have this covered soon.
>
>> I have been testing with mpv and ffmpeg; any thoughts from the
>> Kodi point of view would be most welcome.
> It generally works quite well, but we still have the unresolved
> vaSyncSurface problem.
> To recap: vaExportSurfaceHandle requires calling vaSyncSurface to make
> sure that the decode is actually finished and the buffer is usable
> before rendering the frame. However, vaSyncSurface was largely
> unimplemented on mesa back then and it was unclear how to proceed with
> regard to decode (VAAPI)/present (EGL+GL) synchronization.
>
> So on to the question: Is this still the case, or has there been
> progress on implementing vaSyncSurface in mesa? In either case, do we
> need that support or does this syncing work implicitly somehow on AMD?
>
> I've noticed that mpv does not seem to call vaSyncSurface, although it
> technically should.
Actually the mpv approach is correct.
Calling vaSyncSurface is unnecessary and undesired for AMD hardware
because it moves synchronization to the CPU while it should happen on
the GPU and/or GPU scheduler.
E.g. our 3D pipeline can wait for hardware video decoding to finish
before starting the rendering. We even have some implementations which
allow the 3D pipeline to start when only the first halve of the picture
is decoded etc..
If we don't do this the 3D pipeline runs dry between frame decoding
which leads to problems with power management.
We should probably add a flag or bit or feature or something like this
to note that the application explicitly should NOT call vaSyncSurface
before exporting the surface.
Regards,
Christian.
>
> Best regards,
> Philipp
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