RPi5 "DRM Prime Decoding"

DRM Memory Management — The Linux Kernel documentation

In short, the hardware decoder writes decoded video frames to DRMPRIME memory buffers in a format that allows the same buffer to be (re)used by multiple processes within the display pipeline until the frame is transmitted/output via HDMI. This more efficient than non DRMPRIME decoding where each process in the display pipeline must read (copy) the buffer from memory, do something, then writes data back to memory. DRMPRIME is "zero-copy" decoding. TL/DR: leave it turned on unless you want your RPi5 to work less efficiently. And if you have a problem with something .. this is unlikely to be the cause.