Consumer electronics: Television on a silver platter: A proliferation of options may spawn some orphans in the contest among developers of video disks

High information density — billions of bits etched in a microfine spiral track and then inexpensively replicated in plastic — that's the common denominator of what promises to be the most exciting home entertainment product since color television: the video disk. Together with a shelf-top player that connects to any standard TV's antenna terminals, single video disks can provide half an hour of full color programming per side — complete with stereo or bilingual soundtrack. However, as test marketing gets underway, enthusiasm for the concept could dissipate into pragmatism because several incompatible, independently developed systems now claim preeminence.