http://forum.aufeminin.com/forum/actu1/__f106964_actu1-Une-mere-decouvre-le-secret-d-une-belle-peau-sans-depenser-une-fortune.html
Seriously, the most important thing to keep in mind is that you can't do better than you initial (sources) quality. There exists some layers that could help reenhancing or cleaning your footages such as "sharpen" (in order to bring to light details, mostly black pixels) but you I think would like to search a way to smooth pixels' discontinuity (broken or not smoothed color gradients)
I leave you with the researches because I want you to find it by yourself