You can use viDrop in this page viDrop
s taking care in put MP2
instead of MP3... this converted which is a front-end of mencoder, come with some configurations by default that you can use.
Remember that OndaVX858LE is a rockchip device.
This answer the question you made in another thread here --> Video problem
Concerning firmware you will have to visit Onda BBS here Onda BBS
and deal with Chinese. For OndaVX858LE there are specific firmwares and I don't know of skins for it.