Filmex, the Los Angeles International Film Exposition, opened its sixth annual festival last week with search lights and red carpets, beefeaters and balloons and a bagpiep, carnival performers dressed in traditional costumes, fireworks over a huge fountain, a man who greeted the celebrities stepping out of limousines with inane questions over a loudspeaker, and, oh yes, a movie - The world premiere of Tony Richardson's "Joseph Andrews."

It was just like "old-time Hollywood," said the man with the loud-speaker.

Maybe so. Why shouldn't "the world's largest public film event," which is how Filmex officials describe their handiwork, take its cue from its location in the old time film capital of the world? Nevertheless:

Of the 61 programs devoted to new films here, only 14 are American - but this is mentioned in the Filmex literature as "an outrageously chauvinistic display." Twenty-nine other countries are represented, including the People's Republic of China, Ivory Coast, Argentina, Romania, India and Australia.

The two most anticipated American films at Filmex are "Annie Hall," by New Yorker Woody Allen, and "Welcome to L.A." The latter is set in Hollywood all right, but in the booming record business which, with television, has taken Hollywood's main stage away from the movies.

The most conspicuous center of attention among the celebrities who attended the opening was Cher, leaving the theater alongside "Joseph Andrews" star Ann-Margaret. Cher is not known for her film career.

The Filmex activities that really belong to "Hollywood" are programs and old films - a 50-hour marathon devoted to the kind of musicals they don't make any more, a series of 12 double features devoted to originals and remakes, and a program of recently restored films from the UCLA Archives.

California Gov. Jerry Brown, speaking at the opening, offered the traditional hooray-for-Hollywood remarks expected of any California governor, noted that "while some would wish to look back with nostalgia, I would prefer to look forward," then sat down to watch "Joseph Andrews," a movie set in 18th Century England and filmed in contemporary England.

Most of the festival takes place in the shiny new buildings of Century City, which replaced most of the old 20th Century-Fox back lot. The neighborhood was never actually part of the geographical area known as Hollywood.

This does not necessarily add up to another lament over the grave of the past. When asked by the man with the loudspeaker if it all seemed like "old-time Hollywood," one of the opening guests replied that no, this was "the new-time Hollywood, and it's younger, more exciting and vibrant than ever."

That may sound like extremism in the defense of liberty, but perhaps the man has a point. There is little doubt that Filmex reflects a cosmopolitan, intellectually substantive mood, which would have been very unusual for an official Hollywood institution a decade ago.

Filmex has not always been an official Hollywood institution in its six-year history. In fact, it may just now be approaching that status. At first, the studios were suspicious of something that took film so seriously. Now they buy tables at the opening right ball, where the hoopla seems designed to prove that "Movies Can Be Fun." The Burbank Studios and First Artists chip in with corporate contributions, but so do newer Hollywood institutions like ABC, Atlantic Richfield, Motown and RCA records.

Probably it's just as well that the studios do not rule the roost. This year there is one major activity dominated by contemporary Hollywood figures - a 12-session "Filmusic" conference starring 40 working composers. But as a whole, the Filmex programing reflects an unusually compreming and eclectic view of what movie entertainment is all about.

Filmex includes an 11-program survey of new documentaries, an eight-day "Perspective on French Cinema," four programs of work by AFi film students, fixed programs of artists' films and videotapes and shorts before most of the scheduled features. There are special programs devoted to commericals, movie trailers, Super-8mm film, animation, Japanese ammation, experimental filmmaker Chick Strand, the late Henri Langlois fo the Cinematheque Francaise, the late Peter Finch, the late Fritz Ling, flapper star Colleen Moore (who is expected to attend), and films made by college film students and New York City children. Among the regularly scheduled new features are 25 American premieres and nine world premieres. There were 100,000 admissions last year; at least that many are expected before Filmex ends March 27.

Nagisa Oshima's "In the Realm of the Senses," a film deemed too sexually explicit by U.S. Customs, which yanked it out of the New York Film Festival last fall after the press had already seen it, is scheduled to be seen here March 17. It also appeared at the Chicago Film Festival last year. Presumably the West and Mid-west are less corruptible than the innocent young East.