to avoid quality loss, you generally would like to export clips that will be effected in ae to a lossess or uncompressed format. most people choose the lossless animation codec, but tiff, targa and png sequences will work well too.
however, your hd clips will be huge… if you don’t have the disk space, you can pull clips (or copies of the clips) directly from the capture/scratch folder that fcp put the transcoded mov files in when it converted them from the p2 (mxf) files at import. or look into getting a reference movie out of fcp for the clips you need. fyi, ae will work better (by better, i mean quicker and easier) with the lossless codec or an image sequence than with dvcprohd due to intraframe/temporal compression, but it will work with dvcprohd.
if you’re ae work will be ‘basic motion graphics,’ you may be best off to produce the graphics in ae, render as lossless with alpha (choose straight-unmatted in the output module settings) and then composite those in fcp. that way you’ll avoid any further loss in the dvcprohd footage (remember even if you render lossless out of ae, fcp will still convert to dvcprohd at import, so any original footage will be compressed again). you can use footage for placement, just remove/hide it before render. if you have to render fully composited clips, still render to the lossless codec, or an uncompressed image sequence.
Kevin Camp
Designer – KCPQ, KMYQ & KRCW