Microsoft will start selling a wireless digital music and video player to compete with Apple’s iPod by Christmas. The new player, which Microsoft has been touting to record companies in the last few weeks, will let users download music and videos over the air, according to one source, a feature which would give it an edge over the iPod. Microsoft has also been showing a new media software, developing an application akin to Apple’s iPod/iTunes integrated ecosystem, according to another source.