I am using ffplay.
I solved the problem following this post.
It was about the drivers issues.

Thank you all for your help. You have really enriched my experience.

are you saying you solved something by reinstalling nvidia drivers?
i really don't see how that would solve your original requirement (to force a video player to hard-drop frames).

i might assume that what you call "solved" is that video playback is now smoother?

which is exactly what i said all the time:
HEVC playback without hardware support is extremely painful.
so i guess that by fixing the nvidia driver, you enabled hardware support.

if that was what you wanted all along, you had a Very roundabout way of telling us.

My original requirement is about FFmpeg. I learned from your replies that it is not possible to force FFmpeg to do decoding at a certain fps. It decodes at the capabilities of the hardware it is working on and FFmpeg doesn't drop frames so I cannot notice any miss rate. Therefore, I decided to use FFplay, but I realized that my board had old drivers. Then, when I updated the drivers, now FFplay can decode an HEVC content.

I don't know what you mean by hardware support, because my board (Odroid-XU3) doesn't have HEVC hardware decoder.

Again, Thank you for all your explanations.

yes, i remember you mentioned that.

in that case i don't understand how
this - a post about nvidia proprietary drivers - has ANYTHING to do with your situation.

Yes, this doesn't have any relationship with the initial issue. It just allowed FFplay to decode and play videos smoothly.
So, maybe I should not make this thread as resolved?

what "It"?
you aren't explaining anything.
if you want others to benefit from your solution, you need to share it.

Ok, I screwed up, it was not clear.
I mean updating my hardware drivers allowed FFplay decoding the HEVC content smoothly, that's it.

Thank you