Building a graph for HDR10 output - stumped at sink

Bill Hofmann bill.hofmann at
Wed Mar 30 00:19:50 UTC 2022

Thanks for the very helpful feedback. I am able to connect to kmssink, and
after specifying connector-id and (the correct, I think) plane-id, I get
video out from the non-X view. Defaults don't work there, but that's
manageable. Clearly not yet HDR (haven't made changes to kmssink yet).

HOWEVER, performance is exceptionally poor - whereas vaapisink is able to
keep up with 4k30 P010 without a problem (in a window on the desktop),
kmssink seems to run at about 15fps. As someone relatively new to this
whole process, what's the best way to debug these performance issues?
Looking at debug all the way up to 9, there isn't (of course) any helpful
logged info at least that's helpful to me.  I'll note autovideosink also
has performance issues (but again isn't full screen or non-X).

A little more context - this is an "embedded" Linux situation - will never
be other than full screen video (likely no UI), so there is no need for
interop with desktop functionality.


On Sun, Mar 27, 2022 at 6:05 AM Nicolas Dufresne <nicolas at>

> Le sam. 26 mars 2022 21 h 45, Bill Hofmann via gstreamer-devel <
> gstreamer-devel at> a écrit :
>> So.  What's the next step here? Is this a big gap in kmssink? Is there
>> another sink I should be trying?
> There is no mainline HDR10 support on Linux outside of vendors BSP (NXP to
> note one vendor). Vendors seems to want to compete on this feature, and
> don't really work very hard to come up with generic implementation.
> That being said, if the kmssink is sufficient for your use case, then its
> the smallest way forward, since you don't need a new Wayland protocol and
> compositors support. What I'm uncertain though is if this will work with
> the fact the kmssink code base have aged and isn't using the newest DRM API
> (atomic kms). But other then that, if you have done that in the past, this
> is plain C and mapping the caps field to the DRM properties is all you
> need. Unlike HDR10+, the metadata does not change every frames.
> Regards,
> Nicolas
> p.s. vaapipostproc have a HDR to SDR converter to help improve SDR output
> quality

Bill Hofmann
+1 510 387-0952
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