Which update broke HEVC codec playback?

Hello.

Recently I got a problem with playback of 3840x2160 HEVC Hi10p 60fps videos with DXVA2 Native hardware acceleration enabled. Not a single file, but all such videos that I have.
Same files used to play just fine on exactly the same computers few months ago. I haven't played them in a while so I'm having trouble tracing down which update broke it.

I have 2 computers, one with GTX950 and one with GTX960. Both running Windows 10 x64. Both experience the same issue.
Videos play smoothly for few seconds, then start lagging, and then smooth again. Few months ago all played smoothly.

See below. Both screenshot taken on the same playback session within 15 seconds.

https://i.imgur.com/aV5qgDg.jpg
https://i.imgur.com/nif77GA.jpg

As soon as I disable hardware acceleration and let my i7 do all the dirty job, I have no problem with playback at all, but I don't like 70% of CPU usage, and I want my GPU to do what I bought it for.

When I monitor CPU, GPU, RAM, and SSD usage during playback, it all remains constant no matter if it plays smoothly or lags at given moment.

Since I have only noticed the problem now, how do I trace what caused it?
I keep literally everything up to date, so it could be windows update, K-Lite update, or a gpu driver update.



To summarise, HEVC files played with DXVA2 Native hardware acceleration started lagging for no reason on 2 computers and I have no idea why.

So the clock speed and P-State of the GPU are constant during playback?

Does DXVA2 copy-back behave the same?

Clock speed of the GPU seems to vary a bit, but stays in its highs.
Not sure what P-State is.

GPU-z log: https://www.mediafire.com/?6t89bdceeiup0bw
screenshot: https://i.imgur.com/T5LDPYT.gif

Give me a moment. I will check copy-back in a second.

P-State is Power State.

NVIDIA Inspector is a nice little tool to monitor the GPU.

Yes, It does exactly the same thing on copy-back.

I will check P-State with NVIDIA Inspector tomorrow.

P-State is related to the clock speed. That was pretty stable (and not low), so it does not seem to be a performance issue on the GPU side.

No issues here with a GTX960. But I am using Windows 7. Also haven't updated the driver in a while. Still on 361.

Does it also happen with 8-bit videos? Or 24/30 fps?
You could also try changing the video renderer to madVR.

Here is an example of a file that I tried:
http://demo-uhd3d.com/fiche.php?cat=uhd&id=88

http://demo-uhd3d.com/fiche.php?cat=uhd&id=97

1. I don't have any 8-bit HEVC videos to test (do they even exist?)
2. I tried both of your samples. 24fps one plays smoothly, but 60fps one lags.

Also I just have discovered that the problem I am describing in here only occurs when I have v-sync enabled. When I disable v-sync, it seems to be playing smoothly, but obviously not as smooth as it would with v-sync enabled.

Yes, VSync can cause problems sometimes. That is why it is also disabled by default. In general, it is not really needed. If the smoothness is not satisfactory, then you could try selecting a different video renderer in MPC-HC.

madVR is a very advanced renderer. Its settings are a bit complex and can be overwhelming, but for beginners it is fine to use the default settings.