If you remember back in 2014, MX Player had to take a forced step of removing support for the AC-3 codec (also known as Dolby Digital) from its app. That killed a bit of MX Player’s magic: it had previously been popular as the app that could play any and every video you threw at it, no need to worry about formats and encodings, and regardless of whether or not your device’s own video player could support them.
MX Player adds back AC-3 codec support after the last Dolby Digital patent expired was written by the awesome team at Android Police.