I'm guessing it has something to do with the broken h.264 codec. It's a known bug

#Broken H.264 codec bug!

Problems: (avc bug, h.264 and x264)

0. Artifacts and ghosting
1. There is a shadow left from the last image onto a black scene that comes after.
2. There is a trailing edge of every lighted scene around the picture.
3. The problem is wide, not only related to single app.

I did notice on Xiaomi devices pixelation on videos. I have mi box s 4k and chromecast ultra while there is no pixelation for the same video for chromecast ultra I'm getting pixelation issue for mi box s 4k and redmi note 8 pro. This issue I did notice it for local videos and youtube app (I didn't notice for netflix).

So I did try some methods my self. switching to sw decoding on mx player got pixelation fixed but this isn't precise solution cuz I did read somewhere that hdr is gone for sw decoding and youtube app problem stays.

For Xiaomi devices I did find a video on YouTube. so on mine redmi note 8 pro I did as the video told.

the video did told me to turn on hw overlays so I did turn it on and I got pixelation fixed!!!

https://youtube.com/watch?v=MGxh2vCmR1E

But for mi box When I turn on disable hw overlays I'm getting no screen I'm only getting audio what could be the cause of this could someone help me to turn this on?

Or is there any other solution how I can fix the pixelation?

Update:

İn mi box s 4k There is no pixelation in apps like netflix!!! but vlc, mx player and chromecast built-in playing local video file is the issue getting pixelation in hw decoder!

https://imgur.com/a/OO2R8VI

#####Example:

Hw decoder: https://imgur.com/US8Xzor

Sw decoder: https://imgur.com/fUzwKvw

You can see white line in hw decoder. İn sw decoder the white lines are gone pixelation is fixed but not a permanent fix.

Do you have some new Information about the issue or could you solve it?

Facing the same issue with my mi box and Kodi (or VLC or MX)