HD Video: Correct white balance in post-processing?

As a digital still photographer I am used to shooting my pictures in RAW format. Therefore I can correct my white balance in the RAW converter without degrading the quality. How does this apply to FullHD video? I currently shoot with a Canon HV20 and can set the white balance in advance, but need to know whether I can use a white balance card in my filming and correct white/black-point and white balance after the shooting inside Final Cut Pro without loosing quality. Thanks for your help!