I've seen this player and it's clones all over Shanghai. You don't really need to know the manufacturer as you already know it's a Rockchip player.
To successfully convert video, you have to make sure you have all the parameters EXACTLY right, or you get the file error. Looking at the properties of the working sample video will help.
I'm not an expert, but here is what worked for my Rockchip player. First, none of the converter software worked on my computer. I obtained Fair Use Wizard to convert DVD's to an .avi format, making sure the output was Xvid (
http://fairusewizard.com/lang_en/). I set the output from Fair Use Wizard to the best I could get on the freeware version, but I guess you don't really have to. I found
Then I used viDrop encoder (
http://skss.freehostia.com/) to further convert the down to the right size and audio output. For it all to work, you have to make sure the output size is right (probably 320X240) and the FPS low enough to keep the sound in synch, probably no higher then 22. You have to make sure the output audio codec is mp2. The downside is it takes about two hours to convert one DVD.
If you search this forum, there are more specific instructions and I'm sure the really sharp folks here will correct anything I said that is incorrect. There are some settings in Fair Use Wizard that make it a bit better, as well as viDrop. PM me if you decide to try this route and I'll dig them up. I've converted many DVD movies and they all seem to work fine. Good luck!