The coming weeks will bring a flood of movies on low-priced cassettes as the studios prepare consumers for what they hope will be a Christmas remembered by the stacks of videocassettes under the tree. Even if your tree isn't so graced, you'll at least remember the ads for the movies you didn't get, because the major studios will spend more than $50 million to spread the video word between now and Christmas. While most of the attention and ad dollars will be focused on the $30 movies previously unavailable on video -- including "Lady and the Tramp," "Star Trek IV" and "An American Tail" -- the studios have repriced some of the most popular titles in their catalogues at $30, $25 and even $20, the magic price point for the discount and mass merchandise stores whose shelf space they covet.

All those different prices mean that shopping for video this fall is going to be more confusing than ever. Because of the studios' inscrutable pricing policies, movies that seemed fairly similar to the consumer will have relatively wide price differences for no apparent reason. This year, for example, the sequel to "Poltergeist" will be $5 cheaper than the original -- even though they're from the same studio. And while some of the promotions feature specific genres or performers, most are simply arbitrary grab bags of marketable movies that have nothing in common beyond the studio label.

We'll provide a complete rundown of what's available for how much when it's closer to holiday shopping time. In the meanwhile, one promotion has emerged as the best dollar-per-minute value of the season. Warner Home Video's "The Great Eight" offer cuts the price on eight features that share one easily discernible attribute: length. Of the eight movies whose prices come down to $29.95 in October, only one, the 1951 Marlon Brando/Vivien Leigh "A Streetcar Named Desire," clocks in at a mere two hours. The rest are at least within five minutes of the three-hour mark, and are so long that they need two cassettes to hold their epic entertainments. They are, in order of ascending length: "A Star Is Born" (the 1983 restoration of the Judy Garland musical), "Camelot," "Around the World in 80 Days," "Woodstock," "Barry Lyndon," "The Right Stuff" and "Giant." All but "Barry Lyndon" are offered in hi-fi stereo, most for the first time.

Zzzzzzzzzzz Home video has been a boon to the estimated 80 million Americans who suffer from insomnia, by offering one more thing with which to fill sleepless nights. "The Sleep Tape," due next month, seeks to go one step further by bringing those sleepless nights to an end. Hosted by "noted sleep authority" Dr. Robert Schachter, the 40-minute, $19.95 video offers a five-step route to dreamland. Viewers are shown what causes insomnia, how to identify problem-causing behavioral and eating patterns and how to correct them. There's a lesson called "noise-proofing" your bedroom, followed by a guided relaxation exercise designed to be repeated whenever tension strikes at bedtime. The tape comes from the video division of book publisher Simon & Schuster, whose line of how-to tapes are not the kind of videos likely to suffer a fall-off in rentals if the thing really works.

Basinger's Bad Call Kim Basinger, currently in "Nadine," seems to be best known as an actress whom critics loved in movies that they hated -- the good talent/bad judgment syndrome. Her last mistake, "Blind Date," hits the rental market next month, featuring Basinger slapsticking it up with TV stars Bruce Willis and John Larroquette. If her track record is any indication, it will be a bigger hit on video than it was in the theaters -- her wrong career move of 1986, the Richard Gere disaster "No Mercy," was one of the summer's biggest rental titles.

River Cruise Home exercisers whose minds wander riverward during workouts on their rowing machines can now get a boost from their video screens. "The Rowing Machine Companion," a half-hour, $14.95 video out this month, takes viewers on a trip down the Charles, where they can match strokes with the U.S. Olympic rowing team in both four-man and eight-man shells. Beforehand, there's a stretching session with former Olympic rower Stephen Kiesling. The tape comes from Congress Video, which also produces six road tours for stationary bicyclists who want to see the world from their rec rooms.

Lit Vid "Waiting for the Moon," a fictional look at how things might have been between Alice B. Toklas and Gertrude Stein, comes to video stores next month. Released theatrically early this year, the film stars Linda Bassett as Stein and Linda Hunt as Toklas ... And late September brings three lengthy BBC productions of Jane Austen novels: "Pride and Prejudice," which aired as a mini-series on PBS, and "Sense and Sensibility" and "Mansfield Park," both new to U.S. audiences. Ranging in length from 3 to 4 1/2 hours, the dramas offer generous helpings of spectacular English locations -- just the place to spend a few hours as the fall closes in.