Originally Posted by PeterS
Neither MPEG-2 nor MPEG-4 (AVC) were designed for HD content. They are both retrofits designed to accomplish the task through increasing the bit-rates.
MPEG-2 - designed for NTSC/PAL SD Video. It is what DVDs are encoded in (how do they look?)
MPEG-4 (AVC/h.264) - Designed for internet video conferencing. Increased bandwidth and some spec changes to support additional colorspaces made to support HD. VERY PROCESSOR INTENSIVE.
H.264, which was originally called H.26L, where "L" stands for "long term" or something like that to aim ultimate efficient video codec, putting almost everything known techniques whatever it costs, for long term solution. Engineers indeed very much considered covering from very low bit rate application to higher level application.