This month, millions of people have sat down at their computers and tuned in to watch. . .other people playing video games.

At first blush that may sound as much fun as watching paint dry, but in reality it’s a growing industry. Gaming channels are already a well-established phenomenon in Korea, and the trend catching on in the United States has helped the rise of professional gamers and provided an innovative outlet for charities and companies to promote their latest projects.

Justin Kan is the founder of TwitchTV, which broadcasts live feeds of players doing their thing, often with commentary from seasoned players — sort of the ESPN of this particular “sport.” He said that the site exceeds 16 million visitors per month, and is growing at a rate of around 11 percent every month.

TwitchTV wasn’t originally Kan’s main focus, in fact it was just a smaller part of his streaming site, Justin TV. But once the gaming service launched, he said, “it just kept growing,” Kan said in an interview with the Post. “We noticed and focused more and more on that, then last June we launched a dedicated site.”

Contrary to its name, which indicates a focus on “twitch” games such as first-person shooters that require super-fast reaction, the service provides feeds of folks playing Minecraft, Starcraft and, yes, games like Call of Duty or Halo. Users watch others play while listening to commentary from experts. Kan said he’s trying to get at an atmosphere that gamers coming of age now already know and love; sitting on the couch, watching friends play and critiquing their style.

“It’s very similar to how poker blew up,” Kan said. “We’re making this easy to watch and understand. This is an audience that’s native to the Web and it’s great for this generation.”

Marketers are taking notice. Plenty of AAA titles have turned to the service for online promotional events ahead of launch. For example, 2K Games debuted a new mode on Twitch TV, and even let viewers write in and ask questions of its producers.

“2K Games chose because they have done an amazing job at building a community around people who like to broadcast and watch live games, so it was a great place for us to show off The Darkness II to a massive audience,” said senior interactive marketing manager Elizabeth Tobey.

Charities holding “play-a-thons” or similar events to raise awareness and cash have also found that the site is a good way to promote their causes.

The site has over 1,000 marketing partners and an average viewing time of 47 minutes per spectator — quite the accomplishment in the online video world, where it’s difficult to capture users’ attentions for more than a few minutes at a time. TwitchTV runs commercials during natural breaks in the action — loading screens, set-up, etc. — to get ads on-screen as well.

Kan said the trend is picking up steam in the real world as well.

There are things called “BarCraft” events, Kan said, where users gather to watch StarCraft matches much in the same way sports fans gather to watch the big game.

“It’s analogous to how people watch traditional sports,” Kan said. “There’s a whole community of people doing this.”

Related stories:

Sony’s PlayStation Vita hopes to carve a niche for itself

The tea party, Occupy Wall Street and ‘BioShock Infinite’: How a video game is reflecting life

Comic-Con 2011: Taking The Darkness II from comic to video game