NEON is an advanced SIMD (Single Instruction Multiple Data) instruction set. Think of it as a turbocharger for multimedia tasks. An "Armv7 Neon" codec uses the CPU's DSP extensions to decode video in hardware rather than software. Without NEON, your CPU will struggle to play a 720p video; with NEON, 1080p playback is smooth as butter.
Scroll down to the Decoder section. Look for the option labeled "Custom codec" . 1.49.0 Armv7 Neon Codec For Mx Player