I have an LG OLED TV and a pretty good PC (RTX 2080 Ti + i7 8700k). I've actually been using the combination of madvr + MPC-HC for watching 4K HDR content since the day I bought the TV more than 2 years ago. At the time I had a tad bit worse PC (GTX 1080 + i7 4790k) and I've never experienced any problems also after upgrading my PC till last couple of weeks.

The problem manifests in visually dropping frames when I watch 4k@23.976 HDR (the OSD itself is absolutely clean). There is no problem in 4k@60 though. But the reason I am using 23.976 fps is to throughput the image in 10bit to TV (since there is not enough bandwidth to throughput 10-bit via HDMI at 4k60).

I really don't know what caused the problem in the first place - I try to keep everything up-to-date and update whenever I can (GPU drivers, OS Updates, K-lite updates, even TV still gets his own updates) so I a lot of things could cause it in theory.

I've tried to disable DXVA and use different types of DXVA (for me default option was DXVA copy-back for many years), I've tried to change scaling algrotihms in madvr, I've tried to play with other options but nothing helped. Even when I changed scaling algorithms to the ones with the lowest performance penalties - the result was practically the same (visually it dropped less frames but still it was very noticeable).

OSD in MPC shows no delayed/dropped/glitched frames but I noticed spikes max rendering stats (from 8-11ms to 30-35ms approximately - close to a frame time of 41.71 ms).

So then I started to monitor the GPU frequencies and I noticed that frequencies are actually constantly fluctuating between 400MHz and 1500MHz. So my guess at this point is - the GPU cannot raise frequencies to needed level fast enough thus causing dropped frames. Okay, this problem is solved by locking frequencies at high values. But when i did that ANY 23p content (even 1080p SDR) started dropping frames like crazy. Visually it was a constant 15fps mess. I've tried both changing Power management mode to maximum performance and locking frequencies directly at MSI Afterburner but the result was the same.

Perhaps anyone has fresh ideas about my situation?