The complexity in H.264 gets you later on, when you try to build a complete (e.g. fully compliant) decoder. There are some killer features which seemed like a g

The complexity in H.264 gets you later on, when you try to build a complete (e.g. fully compliant) decoder. There are some killer features which seemed like a good idea at the time, but which make the complexity staggering. MBAFF is a good example (Macroblock-Adaptive Frame/Field encoding). What this means is that the encoder can choose for every block whether it wants to encode it as a single frame or two interlaced fields. Combined with B-frames (and remember that B-frames reference frames both in the past and in the future) this makes for really interesting memory access patterns, which then kills your cache locality and murders performance.