On the current players, you have to turn a disk over to play the other side. When playing such a disk, the laser can focus first on one layer and then on the other without pause. Put double layers on both sides and you have space for, say, a film anthology. All DVD players can handle any of the permutations. It is disk makers who will decide how much material to offer at what price on a single disk and how to put the product on the disk.
Sheer capacity is the main draw.
But most DVD disks also put a menu on the screen that lets you choose from among several languages for the dialogue, or pick a language for subtitles. And in future releases, you may even be able to change the camera's view for a different perspective, a feature that seems most suited for possible instructional disks and travelogues. Getting in at the beginning of a gadget trend is never cheap. The DVD players from Toshiba, Pioneer, Sony, Panasonic, and others resemble CD players and VCRs in size and appearance, and operate somewhat like a CD player. In fact, all DVD machines also play audio-only CDs.