With Robin Byrd, you kind of had to be there. There, in this case, being the red-orange dank no-man’s land of late-night Manhattan public-access cable TV in the ’70s and ’80s. That’s where Robin Byrd, in her black-crochet bikini, with her caramel-blonde hair and white-as-Elmer’s-glue fingernails and spaced-out grin, was the beckoning host of her own proudly tacky and sex-positive showgirl and showboy fantasy kingdom.

She would still be powdering her nose during the show’s opening moments (that’s how understaffed they were), and she would repeat her catch phrases (“Lie back and get comfortable,” “If you don’t have a loved one, you always have me”), and then she would introduce the first performer of the night — what were then called strippers, though this was the only show where that might be a porn queen in a G-string or a blueboy dressed in skimpy biker leather. In the age of triple-X entertainment, there was nothing that racy about it. The slightly outrageous fun is that you were watching this on television — and the fun, as well, was there in Robin’s innocent, giggly, pushy, in-on-the-joke-but-not-quite personality.

“Bang My Box: The Robin Byrd Story,” which recently premiered at the Tribeca Festival (and will drop on HBO on June 30), is the kind of documentary that now gets made because…well, just because. Because 40 or 50 years after the height of porno chic, or what you might call the Renaissance Age of the sex industry (think “Boogie Nights” and the hipification of the AVN Awards), a universe that was once thought of as a guilty pleasure, with performers who provided a service that was the furthest thing from respectable, is now taken more than a little seriously. The people we then called strippers are seen as having fired salvos of flesh against Puritan America. On top of that, the post-#MeToo world has reclaimed sex workers as liberators who were unfairly discriminated against. One of the producers of “Bang My Box” is Sarah Jessica Parker, and the fact that she would lend her name to a movie about Robin Byrd makes a mythological connection that feels right (though a while back it might have felt a little “Say what?”).

Of course, the other cool reason to make a documentary about Robin Byrd is that though she was out there, baring it all on TV, leading a parade of happy exhibitionism, she herself was quite a mystery. She kept her life private; no one knew much about her. It often appeared, from her affectionate kissing and nuzzling of the female performers on her show, that she was queer, but it turns out that in 1976, as she was gearing up to enter the sex industry, she hooked up with Shelly, an advertising art director, and married him. They’ve been together ever since. (She declares in the film that she’s bisexual.)

Because her shows have been broadcast in endless rotation, our first image of Robin Byrd today is a jolt. She looks much older than she did (in the documentary, we see her turn 69 and then 70, always celebrating her birthday with an ice-cream sundae at the totally old-school Serendipity 3 on the Upper East Side), and that’s because she’s a showbiz performer who chose not to get work done. That makes her a rarity and maybe something of a heroine. With her long graying hair and bangs framed by a bun she pins on top, she looks like a warm and cuddly earth mama, and acts like one too. But sitting around in the overstuffed duplex she shares with Shelly, who is now an ancient white-haired man declining into dementia, she gestures toward the wall of tapes of all her old shows and says, “These are all our children!” She doesn’t know what to do with the tapes (there are 600 of them). But by the end of the film, she’s been made to see that they’re documents of a time, and she agrees to archive them. Can someone’s graduate thesis at Oberlin be far behind?

If you were there, watching Robin Byrd on TV, you know that there was something ineluctably winning and charming and honest in its vulgarity — and sexy — about that era, and the people who became the stars of it. Robin started out in porn, appearing in 13 films (including “Debbie Does Dallas”). She took over a show called “Hot Legs” and, in 1977, changed the name to “The Robin Byrd Show.” Most of her guests, like Porsche Lynn and Candida Royalle and Samantha Fox and Annie Sprinkle, were porn actresses who she would interview and humanize. The message of the show was, “Porn stars are people too.”

Because the show was live, you could call Robin and talk to her, right there on the air. It all felt very fringe, but on Channel J, the first public-access channel where you could lease time and sell ads, it became a money thing when she began to advertise phone-sex party lines. Her show leaked into the mainstream like punk. Cheri Oteri parodied her on “Saturday Night Live”; that will make you famous. And as Robin evolved into an ally of the queer community (her show was beamed each week into the West Village gay bar Julius’), she became an activist voice amid the onslaught of AIDS.

She became a different kind of activist in the ’90s, teaming up with “Midnight Blue’s” Al Goldstein to file a lawsuit against Time Warner when their public-access shows were banned for being obscene. This was a freedom of speech case, rather like the one launched and won by Larry Flynt, and it went straight to the Supreme Court. Goldstein and Byrd won theirs too, but watching all this now you think: With the current Supreme Court, is that how it would go today?

At a compact 79 minutes, “Bang My Box,” directed by Jyllian Gunther and Stephanie Schwam, packs in everything you need to know about Robin Byrd: how she was adopted and grew up in Manhattan, doted on by her antiques-dealer father, who died when she was eight, and how she ran away from home to flee an abusive mother, escaping into the hippie ’70s. The photos of her at the time show a smart leonine girl — the Norma Jeane version of herself. Then she went blonde and became a high-camp answer to Marilyn Chambers. She was a comedian at heart, which is why TV agreed with her. She produced and directed her own shows, creating herself as a character.

We probably shouldn’t take Robin Byrd too seriously. Her public-access show was erotic kitsch, and she knew it. It would always end with that week’s gallery of performers gyrating and clowning to “Bang Your Box,” a rock ‘n’ roll song Robin recorded (“Baby let me bang your box”), with her as the ringmaster clown. At the end of the documentary, there’s a montage of Robin today dancing around Manhattan, and she’s as innocent as can be, but she expresses the same spirit she did in those closing sequences of “The Robin Byrd Show,” laughing, with erotic abandon, at her own joy.