AVCHD/.mts editing and conversion help?

[fox's box]

I have a brand new tower mac, a green screen, $700+ in lighting, and i just yesterday i purchased a new camera. but imagine my surprise when the only format the camera outputs is AVCHD witch is unusable in final cut express . i tried numerous programs that claim to convert avchd but after conversion the quality has reduced to unusable! i am at my wits end !

if you can help me find a converter that can convert the video in full 1:1 quality + audio
OR
an editing program that allows me to save the video in a usable format that would be awesome!

i am running mac osX snow, and i am trying to convert the video from a canon vixia HF S21

[edDV]

Final Cut Express will import AVCHD files. In FCE Help, search for AVCHD for instructions.

Final Cut Express does not edit AVCHD natively (1:1 as you say). It converts on import to Apple Intermediate Codec, a diital intermediate format, for editing ease. The AVCHD file is decoded to lower compressed frames causing the file for expand in size to ~60GB/hr.