Q: I want to download movies and watch them on a portable DVD player while taking road trips. Is this possible? Which iPod would be best for this?
A: Firstly, it should be noted that movies that are purchased from the iTunes Store cannot be burned to DVD, so the only way to watch these on a portable DVD player would be to connect your iPod to the player. The simplest way to do this is to ensure that you get a portable DVD player with standard video and audio input jacks and then connect a cable from the iPod to the DVD player, in much the same way as you would for any other video source.
The older, now-discontinued fifth-generation iPod was compatible with a wide variety of video accessories, including some portable DVD players with built-in iPod docks. Further, the 5G iPod supported a fairly standard video cable that could connect to the headphone jack of your iPod and output video from there to the normal video input jacks of a portable DVD player.
The current 2007 iPod models have changed the game in this regard quite a bit. Video output is no longer provided through the headphone jack at all and only specific compatible video cables can enable output through the Dock Connector port. Any of the 2007 models can output video, but you will need to buy the specific Apple Composite AV cables to connect from the iPod to your portable DVD player.