Set your global preference to External . When a file fails, tap the "HW" button on the video overlay to toggle to "SW" manually. For DTS audio on the free version, accept that you must use the internal codec or buy the full app.
If you’re looking for an (or a technical explanation), here are the key points that make “nPlayer + external codec” interesting: nplayer external codec
If you receive a warning that the external codec is outdated, you must download the latest version matching your app's version (e.g., version 4.2.1). Set your global preference to External
Keeps playback smooth even when decoding complex audio formats. How to Install the nPlayer External Codec nplayer external codec