Once bereft of high-def content to play on their new bigscreens, U.S. viewers now have a burgeoning bounty of satellite and cable options to go along with Blu-ray and HD DVD drives.

DirecTV, for one, has thrown down the high-definition gauntlet.

After months of promising upward of 100 HD channels, the satellite provider finally began rolling out its offerings late last month. In the process, DirecTV has gone from offering one of the smallest HD packages among programming providers to the largest: 72 national HD channels and counting.

“We overwhelmingly lead the industry in terms of both quantity and quality of HD programming,” says Derek Chang, exec vice president, content strategy and development, at DirecTV.

In comparison, EchoStar’s Dish Network boasts close to 40 HD channels, while most cable operators average around 20 to 25 (in Los Angeles, for example, Time Warner Cable currently offers 21). In response to the DirecTV channel explosion, cable operators say they’re focusing more on HD on-demand services in addition to the most popular linear HD nets.

DirecTV, which is banking on HD as a chief sales tool in the near future, was able to dramatically increase its offerings thanks to the successful launch of the DirecTV 10 satellite this summer.

Since then, the promise of carriage has prompted several major cable nets to finally roll out HD counterparts, such as FX HD. Additionally, several brand-new networks have bowed in recent weeks directly into the HD landscape, including the all-high-def MGM HD and Smithsonian Channel HD services.

In MGM’s case, the studio was able to take advantage of the suddenly available HD bandwidth to finally launch a domestic channel — a longtime goal for the company, which has operated channels overseas for years. MGM HD will take advantage of the studio’s film library (consisting of more than 4,000 titles) and also hopes to eventually program original content.

“By converting MGM’s sizable library to high-definition, we’ve developed a sustainable business model for an MGM HD channel in the U.S.,” says MGM chairman-CEO Harry Sloan.

In the case of the Smithsonian Channel, the institution struck a controversial pact with Showtime last year; the pay cabler came onboard to produce much of the channel’s original programming. Originally developed as a video-on-demand service, the Smithsonian switched to a linear, HD channel after that marketplace — fueled by the influx of cheaper HDTV sets — began to grow rapidly.

Meanwhile, News Corp.’s new Fox Business Channel recently became one of the first major cable nets to debut in both standard and high-def simultaneously. (The same can be said for Fox Cable Networks’ just-launched Big Ten Network.)

“We’re definitely seeing a lot of demand (for channel space) from the program suppliers,” Chang says. “Large programmers want additional services up,” in addition to the midsized channels that are still putting their HD plans into place. “Plenty of people are asking us for space.”

They’re joining a crowded field. Pioneers like HDNet, Universal HD, Discovery HD Theater and ESPN HD are now part of a lineup that includes newcomers like CNBC HD, CNN HD, HGTV HD and TBS in HD. And premium cablers like HBO and Showtime have seen some of their sister services, like Cinemax and the Movie Channel, also land distribution for their HD feeds.

Several of Starz’s offerings — Comedy, Edge, Kids & Family — also landed HD slots on DirecTV.

The rise of multiple HD services is also forcing some rebranding of existing channels at companies like Discovery Communications. The company’s Discovery HD Theater recently changed its name to simply HD Theater to avoid confusion, now that it has also launched HD simulcasts of Discovery Channel, Animal Planet, TLC and the Science Channel.

And in a twist, Bravo once again has its own HD channel. The original Bravo HD was renamed Universal HD and turned into a general high-def pipeline for all NBC Universal outlets at the end of 2004. Now, Bravo HD is back — as are new HD feeds of sister NBC U outlets USA Network and Sci-Fi Channel.

“I think the competitive environment for viewer eyeballs on behalf of the programmers will force them to continue to add HD at a pretty good rate,” Chang says. “Otherwise they’ll get left behind.”

Most of the pre-existing cable nets’ new HD channels are simulcasts — which means some, but not all, programming, is in HD. (A handful of cablers, including Food Network, currently provide all-high-def feeds for the HD channels that differ from their regular, standard service.)

Over at Fox Cable Networks, affiliate sales/marketing exec VP/g.m. Mike Hopkins says sports drove the company’s early HD plans. That’s why the division launched an HD feed for several of its regional sports networks first, before turning to entertainment outlets like FX.

Then came National Geographic Channel, which made sense because much of the network’s documentaries were already being shot in HD.

“DirecTV, EchoStar and the big cable companies first came to us and said, ‘It would be great if you guys could provide sports in HD,” Hopkins says. “And NatGeo was easy because we made a decision early on to start producing programming in high-def.”

Beyond that, channels that rely on a heavy dose of syndicated fare, like FX, aren’t necessarily programming a lot of HD fare on their new simulcasts just yet. But that will change over time, Hopkins says.

“As you get newer movies and series in, they’re all pretty much in HD,” he says. “This will be a process over the next several years.”