How many times do I need to state that I care very little about 1080p because I don't own any 1080p video. I'm going to try to convert some 1080p today to see if it transcodes faster than real time. It doesn't need to do it with very little impact on the speed of the computer it needs to be able to do it and share it's screen. Again 1080 is only relevant if you have the new Apple TV.
H.264 is a Codec it's how you get to MP4 (MPEG-4) which is one the formats that Apple TV uses..it's called h.264 it's the standard for compressing HD video to include BluRay bluray players need to decode H.264. There are other ways to compress HD video and no the Apple TV won't read them. You can and do use H.264 to compress regular movies also. H.264 is what you use to rip DVD's into you iTunes library also it's is the codec most popular converters use of which Handbrake and Kigo use.
http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC
Your supposed to figure out things by looking at them in context.
Your second comment shows this should be explained.
http://www.apple.com/appletv/specs.html
H.264 video up to 1080p, 30 frames per second, High or Main Profile level 4.0 or lower, Baseline profile level 3.0 or lower with AAC-LC audio up to 160 Kbps per channel, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats
MPEG-4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats
Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, audio in ulaw, PCM stereo audio in .avi file format
I've spent enough time in timeout recently so this is the last post of yours I'm going to respond to becasue I'll no longer be able to remain polite.