Roku is once again the top seller of media streaming devices in the U.S., but Google Chromecast is quickly catching up. The dongle slid past Apple TV into the No. 2 spot for sales in 2014, a report this week said. 

As sales of Chromecast rise, Roku and Apple TV have both seen their share of the market fall through the first three quarters of the year, according to Parks Associates, a market research firm. Roku's market share stands at 29 percent, down from 46 percent last year, while AppleTV holds 17 percent, down from 26 percent in 2013.

Chromecast, on the other hand, now accounts for 20 percent of the market after not registering in Parks Associates' 2013 numbers. The Amazon Fire TV has also emerged as a major player, holding down 10 percent of market share since its launch in April.

With a price tag of $35, the Chromecast is one of the cheapest streaming devices available. By comparison, the Apple TV and the Amazon Fire TV are both $99, although Amazon also recently introduced a $39 Fire TV Stick. Roku, meanwhile, offers streaming devices that range from $49.99 to $99.99.

Roku and Apple can't be thrilled about losing market share, but fortunately for them, U.S. sales of media streaming devices continue to keep growing. Through three quarters, 2014 sales have already matched those of last year. That's an indication that media streaming devices will be popular gifts this holiday shopping season, the report said.