How do I know if I encountered CPU performance issue or hardware decoding capability issue?

I have M1 iPad running iPadOS 15 Public Beta4 and I downloaded 144GB 8k hevc video, and I encountered glitch.
I wonder if M1 iPad is capable of hardware decoding 8k hevc videos?
Or if Infuse is using software decoding and M1 is not powerful enough?
Or it’s a iPadOS 15 compatibility bug?
How do I know which one did I encounter?

Downgrade to iOS 14.7. If the problem exists try another player such as VLC. If problem persists then it’s most likely something with hardware