How to play the video files? All gets invalid file format
 

I have downloaded the Rockchips's 21 Sample files , and they All Worked!
Variant C , Small videos appear with black borders.

So I want to know what to do now? how to convert any videos so I can play them on my MP4? Firmware:
13.0...x.x.x.x.xxxx.x....etc
Chipod
Not Original , MP6 Gameplayer . Based on one of the RK27xx

figured that out , downloaded convertor , but now it has a clicking sound every second! and on large videos , it is shaving machine sound!