A new report from International Data Corp. (IDC) shows that the “media tablet” market isn’t as strong as previously thought, though the iPad is still the most dominant device.

[ad#Google Adsense 300×250 in story]IDC reports that worldwide shipments of media tablets fell by 28 percent sequentially in the first calendar quarter of 2011 to 7.2 million unit. IDC raised its overall forecast for 2011 from 50.4 million to 53.5 million units, however.

IDC attributes the sequential drop in sales to seasonality, something they’ve seen before in the e-reader market (devices like Amazon’s Kindle and Barnes & Noble’s Nook).

The iPad and iPad 2 “dominate the media tablet market,” according to IDC, which added that Apple’s shipments for the quarter were below expectations. The company attributes that partly to “supply-chain hiccups” and also to Apple’s pre-release announcement of the iPad 2, which may have had an effect on consumer demand.

Android-based media tablets grew to 34 percent of the total market, an 8.2 percent sequential increase.