Vudu, maker of the eponymous video-on-demand set-top box, is adding a few hundred pixels to some of its HD titles--dubbed HDX--challenging rival Apple TV, which is lagging 350 pixels behind.

Starting Thursday, the Santa Clara, California, startup will offer 65 HDX titles at 1080 pixels--close to Blu-ray, the highest HD quality available now--while rival Apple TV stays at 720 pixels for its HD titles.

“HDX titles have been encoded at a much higher bit rate, producing a higher quality image,” said Patrick Ellis, a senior product manager at Vudu, adding that the company is planning to rapidly expand its HD library, which currently counts a little under 400 titles.

Vudu’s standard library counts over 10,000 titles-- five times more than Apple TV.

Apple offers a bigger selection of HD titles, about 500, but is missing the extra pixels.

The difference of 350 pixels might get lost on those satisfied with the standard 480-pixel definition, but sharp-eyed videophiles and HD TV owners might appreciate the effort.

“The HDX versions of Vudu movies are insanely sharp; they make standard films look blurry and washed out by comparison,” said David Pogue, The New York Times technology columnist.

The HDX flicks will cost the usual $4 to$6 that the company charges for lower bit rate rentals, but they are so data heavy that, depending on the Internet connection, it takes 2 to 3 hours to start--compared to under a minute for other formats movies.

It remains to be seen if users will choose to wait a few extra hours to watch an HDX movie when they can get direct access to the lower bit rate version of the same movie instantly.

The company said it plans to expand its HDX library to all its standard HD titles.

The initial 65 available HDX titles include, among others, movies such as The Fast and the Furious, The Chronicles of Riddick, Speed Racer, Chinatown, Casino, Fatal Attraction, and Close Encounters of the Third Kind.