Please see the settings below which I have found work all the time when using Xilisoft's DVD2MP4 converter, for creating movies to work on my Rockchip players.
320x240 pixel players [e.g. 2.4", 2.8" and 3.0"]
224x176 pixel players [e.g. 2.0" and 2.2"]
And here's what my Rockchip players look like, in case you were wondering! (2.4" at the top and 2.0" at the bottom)