I have written a tutorial on how to convert video for rockchip players. You can select the resolution sizes so it works with all size players. You can get it here
http://www.mympxplayer.org/how-to-vt3183.html
Or if you prefer the simplicity of "Drag and Drop" type programs I uploaded the AviConverter v2.1 for you here
http://uploaded.to/?id=tclxw6
Dave