[AC Question]

Let me explain my problem and ill ask my queston along the way. so basically, i recently bought an anart sports camera and every time i use the wifi on the camera through the phone, i save my videos and transfer them towards my samsung s5 phone gallery. It keeps telling me when i review back my video that there is no audio or say's, "Audio Codec." Than i was thinking if i upload it to instagram it would play the audio, but no luck there too. I also tried using mxplayer and it works fine but the thing that sucks is i cant save them to my phone gallery. Is there any way i can fix this problem? I need help real bad.
-Thank you