The original musical opening to PBS’s “Masterpiece Theatre,” by the 18th-century French composer Jean-Joseph Mouret, is a stately theme that suggested a formal march of peruked dandies in high heels. That has given way to a new theme for full orchestra that references the first notes of the Mouret tune, then blathers on in generic Hollywood soundtrack fashion.

One might expect the long-standing television franchise (next year marks Masterpiece’s 40th anniversary) to have similarly degenerated. But what has now been rebranded “Masterpiece Classic” remains remarkably strong, especially when it stays close to its unfashionable, anglophile fixations — period dress, proper accents, class snobbery — churning its way through the great, plot-dense novels of the 19th century.

Next up, Jane Austen’s “Emma.” It’s been done before on TV and the big screen, including two 1996 film versions, a teeny-bopper update called “Clueless” in 1995 and a 1972 BBC miniseries. But “Emma,” one of Austen’s most challenging novels, offers endless fodder. If you’re tired of Emma — the rich, witty and narcissistic meddler in other people’s affairs — you’re tired of the world.

The current version, starring Romola Garai, didn’t fare very well when first seen last fall in the United Kingdom. The Independent asked, ominously, “Has the costume drama had its day?” One critic found, among other faults, the following distractions: flowers blooming at the wrong time of year, a misquote of Milton and an inappropriate “south-London” accent coming from the over-wide mouth cavity of Garai.

Still, this “Emma” is a delight. The costume drama might be subject to the most merciless scrutiny, but that, in a way, is a mark of its lingering status. “Emma’s” occasional anachronisms are like those points divers or gymnasts lose for doing things mostly imperceptible to any human eye not trained in the minutiae of the sport.

Reality TV, which is often explained in financial terms (it’s cheaper to produce than scripted drama), has made “Masterpiece” look better than ever. The economic explanation isn’t just a matter of the bottom line in the network budget. The problem with reality TV is that its characters are poorly capitalized. There simply isn’t enough background, drama or depth invested in them to make their conflicts interesting.

The arcs of time over which series such as “Emma” transpire empower their actors. Garai, whose mannerisms are without a doubt anachronistically over-animated for a member of the English gentry, also knows how to build a character (or rather unbuild it) with the slow accumulation of wisdom and self-revelation. The 21-year-old Emma, Austen tells us, is “handsome, clever, and rich, with a comfortable home and happy disposition.” Emma has everything except an accurate sense of her estimable self-worth and the value placed upon her opinion by those less fortunate. Garai, rather magically, manages to reveal Emma’s charms, and her weaknesses, without losing the viewer’s sympathy or interest — but it is a long process.

As her friend and sometime scold, Jonny Lee Miller’s Mr. Knightley keeps enough in reserve over the four-hour drama that it is genuinely thrilling to see his power over Emma’s conscience in the last episode — proof that a single raised voice can have shattering power if the producers and actors are committed to the discipline of long-form pacing.

These series are also a last refuge for the delights of character acting, which is very different than the caricature acting that defines most small and comic roles on TV. Without her bores, boors and preening twits, Austen’s fiction would be the stuff of Hallmark cards. But few of her bores, boors and preening twits are utterly irredeemable, which makes them a major challenge. And so Emma’s father, a fussing and fretting waste of skin played to delicious limits by Michael Gambon, emerges as a damaged man, not a repellent one.

Even when the directors and screenwriters are guilty of heinous crimes against literature, the gambols of great character actors can redeem a costume drama.

The curious thing about the persistence of quality on “Masterpiece” is you sense how badly PBS would like to ruin it. The introductions, by Laura Linney, are the most ridiculous twaddle about real people and real feelings, as if Austen wrote in Sanskrit about Martians. Hovering over the series is the manic fear that somehow the public is too stupid to understand Austen’s characters on their own terms. Hence, on the PBS Web site, “Emma” screenwriter Sandy Welch reassures us of something that, if true, would reduce the miniseries to irrelevancy: “They think in the same way we do, and they act in the same way.”

Fortunately, the product suggests that the people who make these dramas don’t believe this. Of course Austen’s characters don’t think and act like we do. They are obsessed with details of dress, decorum, class and propriety for which there is no contemporary analogue. Which is why we read Austen. And for now, why we watch, too.

“Emma”

Based on the novel by Jane Austen and starring Romola Garai and Michael Gambon.

When: 9 p.m. Sunday

Where: OPB and OPB HD