VIDEOSCAN. A selection of new releases for sale or rental

THE OUTER LIMITS: NIGHTMARE (1963. Directed by John Erman. MGM/UA Home Video) - This episode of ``The Outer Limits,'' one of network TV's most highly regarded science-fiction shows, is so ambitious it almost sinks under its own weight. But not quite. The heroes are a six-man ``multinational strike force'' from Earth, captured on the planet Ebon by what the program notes call ``satanic, batwinged, gargoyle-like'' extraterrestrials. The script drags in so many subplots and psychological nuances that the story gets scrambled, but there are more surprises and subtleties than most TV shows dream of. The cast is also impressive, with Martin Sheen, James Shigeta, and Bill Gunn in key roles. - David Sterritt TANNER '88 (1988. Directed by Robert Altman. HBO Video) - The first three episodes of a pitch-black political comedy, made for HBO television and originally shown when the real-life 1988 campaign was heading into the primaries. The series was written by ``Doonesbury'' cartoonist Garry Trudeau and directed by Robert Altman, of ``M*A*S*H'' and ``Nashville'' fame. It gets off to a slow start, with jokes and vignettes that are more timely than funny. It improves as it goes along, though, and the third portion has some surprisingly pungent scenes. Michael Murphy is suitably cast as Jack Tanner, a candidate who genuinely believes that image and substance are pretty much the same thing. Visually, this is the most sophisticated work Altman has done in years, and the script makes up in prescience what it lacks in consistency. - D.S. MABEL MERCER: A SINGER'S SINGER (1988. Produced and directed by Lou Tyrrell and Leah Jay; View Video, 34 E. 23rd St., New York, NY 10010) - The word ``soul'' suits the late cabaret artist Mabel Mercer to a T. Mercer's career spanned almost 70 years, in the United States and Europe. She was always capable of touching her audience in a very special way. In this performance, taped at Cleo's supper club in New York in 1981, her vocal powers are waning, but her performance is as evocative, humorous, and subtle as ever. She is sensitively accompanied by the late, great pianist Jimmy Lyons.

- Amy Duncan THE BEST OF ERNIE AND BERT (Produced by Sonia Rosario; directed by Jon Stone; Random House Home Video) - Two of the Muppets star in this collection of skits from ``Sesame Street.'' The vignettes are tied neatly together by Big Bird and others looking at a family album in which the photos come to life. Among the most delightful: Bert and Ernie's visit to the pyramids, where an ancient statue begins singing and dancing with Ernie - but only when Bert's not looking. - A.D.