Open MX Player, go to Settings > Decoder , and scroll to the bottom. Look at the Custom codec field to confirm it asks for "ARMv8 NEON" .
neon64-1.49.0-build_2.zip (Specifically for 64-bit ARMv8 devices). How to Install the 1.49.0 Codec MX Player Custom Codec 2.7.x armv8 neon codec for mx player 1490 top
MX Player requires a codec that matches your device architecture and the specific version of the app . Open MX Player, go to Settings > Decoder