The second-generation Apple TV is capable of decoding and playing back 1080p video, according to a discussion thread on Mac Rumors’ forums. Users of the new set top box report that iTunes accepts 1080p content, which can then be streamed to the Apple TV 2G. While some 1080p material has caused the Apple TV to struggle—likely because of a higher bit rate than other 1080p files that did play without issue—it is encouraging that the…