Movies on the move

You want to watch what you want, when you want to watch it. That's why you have televisions in the living room, home theater, bedroom, kitchen, exercise room and den, and maybe even the garage and bathroom-not to mention TiVo and DVD players-and why networks are putting some shows on their Web sites. It's also why some geniuses invented portable DVD players, and why more and more of those miniature marvels are showing up in corporate and private jets.

True, some such jets feature highly sophisticated built-in entertainment systems, with multiple high-definition DVD players, iPod ports and satellite-direct radio and television. But what if your setup is more modest? Or you have two large-screen monitors but passengers want to watch four different movies?

That's when you'll be glad to have aboard one or more portable DVD players. They're particularly handy when kids are in the cabin and in parts of the world where satellite television has no coverage.

The basics are pretty standard: a liquid-crystal display (LCD); a holder for the DVD; and an array of controls to start, stop, pause and adjust the picture. Beyond that, though, there are lots of alternatives. Here's what to consider:

Design. Flip-up models are similar to small laptop computers and are arguably preferable to tablet-style players where the screen is left unprotected during storage. Many players have a slot for the disc or a disc tray that emerges and retracts from the side or front. Some users, though, prefer a flip-up disc cover, pointing out that DVDs have been known to get stuck in the other mechanisms.

Picture quality. A player with 480-by-234 lines-per-inch resolution can't reproduce all the detail from a disc, resulting in a slightly fuzzy picture. Screen resolution of about 1,000-by-600 will deliver a much sharper image. Keep in mind that the player itself may be capable of better resolution than the screen can display-and that may matter if you ever connect the unit to a higher quality external monitor.

Outputs. Some players have two headphone jacks, while others have dual jacks for external speakers or an audio splitter with a single plug and two headsets. The more outputs the better.

Formats. Some portable DVD players accommodate a wide variety of audio and video formats in addition to standard DVD, including DVD-R and CD-RW as well as MP3 music and jpeg picture files.

Speaking of formats, a market war is raging in the DVD world that recalls the 1980s battle between VHS and Betamax. The battle concerns whether Blu-ray or HD-DVD will become the next-generation optical disc format. Both technologies produce superb video, but they are incompatible and neither is yet available in portable models. The good news is that you don't have to worry that your videodisc collection will become obsolete. Both Blu-ray and HD-DVD players will be backward compatible with today's discs, designers claim.

Size and weight. A simple DVD player with a 3.5-inch screen may weigh slightly less than three pounds, while a top-of-the-line unit with a 10.5-inch screen could weigh more than twice as much. With accessories, a disc collection and a carrying case, the package may come close to 10 pounds-or even more if, like some players today, the one in question has two monitors. Obviously, there's a tradeoff to consider here: You want something big enough to watch comfortably but small enough to be truly portable.

Battery life. Lithium-ion batteries are best and most common and typically last about 2.5 hours between charges, but some players have batteries that operate for five hours or more. If you like a player's features but not its battery life, one solution is to carry a spare battery. Another is to purchase a player with an AC adapter. Both ideas somewhat defeat the idea of portability, but they're nice fallback solutions.