Hiya i would sugest using Handbrake.
What i do is change the video output to 320/240 if video 4/3 and 320/180 for widescreen.
These Match the Dingoo A320 screen, also set the Bitrate to about 1/3rd of original or say 300-400, the quality reduction is not noticed much on the Dingoos small screen.
By dropping a 640X Video @ 900BR to 320X and 350BR you can reduce the file size by 60% and it would still look half decent.
As for Codecs well MP4 (MPEG4) or XviD work fine.
