H264 as is uses interframe compression which is completely unsuitable for use in Catalyst. Interframe compression uses interframe prediction to make use of redundancy between neighbouring frames, and thus achieve higher compression ratios. Interframe compression codecs use a series of frames which are interdependent on each other called a group of pictures (GOP) structure. This comprises of Intra (I) frames, Bidirectional (B) frames, and Predictive (P) frames in a particular sequence. This is why it is tricky to playback MPEG-2 backwards or do Inframe/ Outframe stuff with it.

H264 is also rather processor intensive to decode.

Catalyst likes codecs that use intraframe compression where the frames use spatial compression only, such as DV, Photo-Jpeg, AIC, ProRes etc.

AIC is a bit old school. You are much better off with ProRes Lt or Proxy. They are 10 bit, 4:2:2 and look much nicer than AIC, which is 8 bit, 4:2:0. Also ProRes supports hyper-threading. Macs love ProRes of any flavour, but ProRes Proxy gives blistering performance on Catalyst.

Hugh