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. After the removal, users had to download custom-built codecs and manually point the app toward them as a make-do solution to gain back AC-3 capabilities.

Finally, on March 20, the last of Dolby's patents over the AC-3 codec expired. You can read more about it on AC3FreedomDay (the page appears to be down, so we're pointing you to a cached page). And that left MX Player free to add back support into its app, which it proceeded to do swiftly.

The team announced it on the XDA forums saying that version 1.8.17 of MX Player and 1.8.16 of MX Player Pro both have it working. All you need to do is restart the app with an active internet connection and the configuration will be updated to enable AC-3 playback. All of your local videos and even streamed ones with AC-3 audio should play normally with sound.