The audio codec describes how sound is encoded. It is separate from the selected language or output device.
The 5.0 includes an Info tab in Viewing options for video details. The tracks panel’s Audio tab provides track selection and sound controls.

Earlier codec reference
The earlier Windows guide listed AC3, AAC-LC, HE-AACv1, HE-AACv2, MP3, MP2, MP1 and Ogg Vorbis. This is a historical reference, not a guarantee for every file in 5.0.
For sound problems, note the track and output device and contact support@cnxplayer.com with file and device details.