Enjoying two sides of Japanese film -- pensive and epic; Also: an unabashed polemic, an odd thriller, a Cukor tribute

The two poles of Japanese film are represented by a pair of movies just going into wide American release. Muddy River, directed by Kohei Oguri, reflects the contemplative and delicately framed style associated with such filmmakers as Ozu and Kinugasa. A 1981 nominee for the ''best foreign-language film'' Oscar, it has now been issued in the United States.

By contrast, Seven Samurai embodies the sweeping epic tradition exemplified by its maker, Akira Kurosawa. First released in 1954, it has hitherto been seen by Americans in a drastically cut version. Now the full-length edition, running almost 31/2 hours, has been issued by Landmark Films.

Set in 1956, when Japan was still struggling to its feet after World War II, ''Muddy River'' gives a muted chronicle of working-class life as seen through the eyes of a little boy. His adventures are small but resonant - he witnesses an accident, makes a new friend, passes through a family crisis he dimly understands, loses his new friend. These incidents are depicted through carefully composed yet matter-of-fact images that suggest hidden emotions and complicated meanings without actually thrusting them before the viewer.

The result, though a small film, is subtle and sturdy, managing to be childlike without romanticizing or sentimentalizing its young characters. It never gathers the momentum of Ozu's best work, and it falters near the end with some harsh images (live shellfish set afire by a thoughtless boy) and a trite story twist involving a prostitute.

Despite these flaws, however, ''Muddy River'' is an impressive debut by a promising new director, and a heartening sign that high-quality work can still take place outside the rigid and conservative Japanese studio system.

Even in its truncated version, ''Seven Samurai'' is a recognized classic, and it certainly packs a wallop at its full 208 minutes. This is not to overpraise it, or overlook its failings - overlong scenes, murky plot developments, and too much hysteria in some of its frantically stylized performances. But its pace is brisk, its visual style ranges from impressive to indelible, and it packs more laughs than you'd ever expect from a rip-roaring yarn about medieval mayhem.

It's still a major Japanese monument, and a healthy tonic after Kurosawa's recent ''Kagemusha,'' which never soared above its lavish but sadly stuffy style. Missive on missiles

Political documentaries usually fall into two categories.

On one hand is the ''balanced'' sort, giving both sides of the story and inviting the viewer to decide between them.

Then there are the polemics - the films that aren't ashamed to bare their convictions as soon and as often as possible. While these aren't always fair, they often gain in passion what they lose in perspective. Good ones can be provocative to watch even when their ideas are infuriating.

America - From Hitler to M-X falls into the second group. Its director, Joan Harvey, wants to convince, not just educate. She musters a lot of evidence for her argument, hammers it home, and gives barely a nod to the opposition. Whether you agree with the film or not, it's bound to stir your thoughts; and if only a small part of its points and allegations are true, then it's a badly needed contribution to current debate on crucial issues.

The film focuses on the ''military-industrial complex'' that Dwight Eisenhower warned about. The gist is that American industrialists have a vested interest in the nuclear-arms race - an interest that's a logical extension of American ties with Nazi Germany beginning in the 1930s.

As before, says the Harvey argument, anticom-munism makes a handy cloak for the ruthless pursual of war-related profits. And already, the film contends, citizens are suffering from the nasty byproducts of nuclear stockpiling, including such blunt dangers as heightened radioactivity levels and such subtle effects as national demoralization in the face of potential nuclear holocaust.

In socking its contentions across, ''America'' largely avoids the cloying emotionalism and simplistic reasoning that marred the last Harvey polemic, ''We Are the Guinea Pigs,'' an attack on the nuclear-fuel industry, in which arguments were avoided more often than won. Whatever one's response to her rhetoric, it's good to find more maturity in her style, and to see new signs that film is alive and well as a medium for social and political debate.

Now showing or due soon in a number of American and European cities, and already the veteran of many film festivals, the new Harvey outcry is likely to arrest attention wherever it travels, though how many it convinces is another question, with a less predictable answer. Odd duck of a film

For both good and ill, Winter Kills is larger than life. Its images are outlandish, its story is byzantine, its performances are extravagant. And it includes something, however momentary, to offend just about everyone - in terms of propriety, politics, artistry, or plain old taste.

It's an odd duck of a movie. But it just won't go away. First released in 1979, it was ignored by audiences, though praised by some critics. It floated around for a couple of years, gathering a ''cult'' reputation, and appeared in a ''sidebar'' to the 1981 New York Film Festival. Now the distribution rights have been acquired by its writer and director, William Richert, and he has tossed it back into the marketplace - with a slightly altered finish - hoping for success at last.

The plot is hard to follow, much less describe. Jeff Bridges plays a quiet young man whose half-brother, a president of the United States, was assassinated years earlier. As new evidence surfaces, our hero tries to track down the killers, and finds the bizarre trail leading toward his own family, dominated by his super-wealthy father. Other characters include the father's henchman, the hero's girlfriend, and assorted thugs, mostly comical. In the cast are such notables as John Huston, Anthony Perkins, Eli Wallach, Ralph Meeker, Richard Boone, Toshiro Mifune, Dorothy Malone, Sterling Hayden, and Elizabeth Taylor in a small role.

I doubt if ''Winter Kills'' will ever succeed with a really wide audience. Its atmosphere is too heated, its energy too heightened, its style too flamboyant for current moviegoing moods. While some portions have a dreamlike grip, others set new heights in brazen self-indulgence. Also, its harsh language and brief but noisy sex scene will put it still further off limits for many.

The filmmaker disagrees. ''People are starved for something that will make them think, and give some real dialogue to listen to,'' Richert told me the other day. ''And this movie says things that have to be heard,'' he continued, referring to its view - sometimes cautionary, sometimes downright paranoid - of American government as a tool of special interests and wealthy connivers.

Still, he's playing it safe. The reissue of ''Winter Kills'' is proceeding cautiously, traveling to hand-picked theaters in carefully chosen cities, beginning with a respected ''art house'' in Manhattan. The idea is to build interest by appealing to a limited audience of supposedly ''thinking'' viewers. A broad release will follow, as well as the reissue of yet another Richert opus, ''Success,'' completed about the same time as ''Winter Kills'' but never distributed despite a cast including Jeff Bridges, Ned Beatty, and Bianca Jagger.

The making of ''Winter Kills'' was an adventure almost as surreal as the movie's plot: According to the director, the producers made false financial claims, and the production ran out of money long before completion. He spliced together whatever footage he had, spent years raising money for a little more shooting ''to fill in some of the gaps,'' then edited the result by ''ruthlessly cutting out anything that bored me.''

No wonder it's such an eccentric picture. But there's no denying Richert has a real moviemaking talent, and the chutzpah to back it up. ''If you want to take a chance these days,'' he says, ''Hollywood gets upset and says you can't do anything so preposterous. But why do we still enjoy all the old, classic movies? Because they were preposterous!''

He has a point. Meredith Monk film

When she isn't busy singing, composing, dancing, choreographing, or playing the piano, Meredith Monk makes movies.

Her latest is an exquisite short called Ellis Island, which deserves to be widely seen. And unlike most shorts, it will be - on Feb. 2, when it's scheduled for a nationwide airing (PBS, check local listings for time and channel)m. It has already appeared at film festivals and won three prizes.

Focusing on the American past, ''Ellis Island'' is both an elegy and a celebration. It remembers with sadness the loneliness, bewilderment, and undignified treatment that marked the entry of so many newcomers to the United States when that tiny chunk of land served as a checkpoint, processing station, and human warehouse for the immigration authorities. Yet it cheers the courage and conviction that saw the newcomers through, picturing them as stalwart pioneers determined to set down new roots as firm and deep as their old ones.

All this is evoked wordlessly, through precisely chosen images punctuated with delicate snippets of Monk music. Not all the movie's ideas are as fresh as they could be: It's rather ordinary to alternate black-and-white images with color, for instance, to contrast past and present. But its moods are engaging and its tone is irresistible. As an introduction to the Monk style - of both music and dramaturgy - it's invaluable. As a movie in its own right, it's a small gem. A touch of directorial class

More than one critic borrowed a phrase from ''The Philadelphia Story'' to sum up the late George Cukor's favorite theme - ''the privileged class enjoying its privileges.'' For more than five decades this elegant and inventive director gave Hollywood a touch of class that appealed to moviegoers of all tastes. It was a distinguished career in every sense.

Cukor made his directorial debut in 1930, just as talkies took hold for good. It was a fitting coincidence, as he loved good dialogue and took pride in working with the best screenwriters Hollywood had to offer. He disdained the view that words are a second-class element in cinema. His movies celebrated language as well as images.

The humility he felt before first-rate screenwriters extended to the great performers he worked with, too. He became known as a ''woman's director'' for guiding such stars as Greta Garbo in ''Camille,'' Katharine Hepburn in ''Little Women,'' and Ingrid Bergman in ''Gaslight.'' Yet men gave him memorable performances, as well, from W.C. Fields in ''David Copperfield'' to Spencer Tracy in ''Adam's Rib'' and ''Pat and Mike.''

Cukor had little use for high-toned critical theories that enshrined him as a directorial ''auteur'' with a profound style all his own. In an interview with him a few years ago, I spoke well of his 1941 comedy ''Two-Faced Woman,'' and he wouldn't hear a word of it. The next time we met, he jokingly remembered me as ''that intellectual young man'' who had found something to admire in a movie that just wasn't worth the candle.

Cukor directed more than 40 movies, including TV films - ''Love Among the Ruins'' was one, with Hepburn and Olivier - and wrapped up his career with last year's ''Rich and Famous.'' He occasionally appeared to be ahead of his time: The 1935 ''Sylvia Scarlett'' anticipates the current ''Tootsie'' in more ways than one, and his definitive ''A Star Is Born'' probably hasn't seen its last remake yet.

But mostly he was in and of his time, reaching out to all audiences with his crisp approach and fluid style, while often revealing a reflective mood by taking show business and entertainment as his very subject matter. He was a director of taste and cultivation, and Hollywood will be the better if his influence - already considerable - continues to grow among younger generations of filmmakers.