The STB uses the Sling transcoder to convert your content to a compatible format, then the app wireless boots a sub-HD version to your portable device.
The JVC can record and play in standard DV format and convert its own high-def recordings on the fly for playback at lower resolution on old-fashioned TVs.
However, if you've ripped CDs into AAC using iTunes, you will be able to play them back in the NW-E005 without having to convert them into another format first.
With its early audio players, the company actually expected customers to dutifully convert (using software that is generously remembered as buggy) all of their song files into a proprietary format that the players could play.