[Mesa-dev] 10bit HEVC decoding for RadeonSI v2

[Christian König]

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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