libhb: New denoiser, nlmeans.

Non-local means averages multiple patches of similar pixels together, preserving similarities and attenuating variance (usually noise). This is typically more effective than lowpass and more faithfully restores the appearance of structure and detail found in the original source, especially in the high frequency range. Parameters for origin patch weight tuning and pre-filtering further improve on the original algorithm.



git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6216 b64f7644-9d1e-0410-96f1-a4d463321fa5