Let me just provide some corrections and clarifications
Originally Posted by crazygreekangelo
H.264 is an video codec
Alternatively, if you prefer, you can state it as being a MPEG4 compression format. Some background:
, and it is used for the majority of high definition video (Blu-Ray, HD-DVD, OTA HD).
AVC/H.264 is indeed one of the three potential compression formats that you may find on either a Blu-Ray or HD DVD disc (the others being MPEG2 and VC-1). What codec the studio actually uses is free to their own decision, but I'm not certain that AVC/H.264 constitutes the majority choice -- more likely a fairly balanced split between the three currently.
As for OTA HD: for European countries (and elsewhere around the globe), where development of digital tv services was late in coming, adopting AVC/H.264for their DVB broadcasts is fairly easy decision given that they are not encumbered by legacy MPEG2 systems already in place....so AVC broadcasts are indeed beginning to pick up steam.
On the other hand, countries (such as the US) that were early adopters of digital television now have a large installed base of MPEG2 systems in place. This is a particular reason why the ATSC (the committee) is only now considering the adoption of AVC/H.264 (and others) for in the future...but for the time being (likely a number of years to come), ATSC (the standard for OTA broadcasts in America, Canada, S.Korea) is strictly MPEG2 based.
H.264 (.mp4) files
careful here .... .mp4 is simply a file container format. While H.264 encoded content is often placed in a .mp4 container, you could also place it in other container formats too (such as .mov, .mkv, .avi, ....)
.mov files are H.264
again, clarification is needed here. As stated just above, .mov is a container format. And while Apple has indeed developed their own implementation of the AVC/H.264 codec, this does not mean that all .mov container files are stuffed with H.264 encoded material ... indeed, the actual content could have been encoded by using several other compression formats.
The main advantage to H.264 is that high-resolution video can be compressed into a very small file with high quality. The downside to this is decoding the file for playback take an enormous amount of processing.
This is quite correct. I would only add that the compression process (i.e using AVC/H.264 to encode the video content) is also quite process intensive as well.