# Avisynth script by J. Beale, Nov. 2005 www.bealecorner.com 
# Rename script to end with .AVS prior to use

# Objective: reduce noise near dark level prior to MPEG2 encode
# brightest pixels (here, above level 150) are completely unfiltered
# source: downconverted HDV exported from Vegas 6c via DebugMode Frameserver


Orig = AVISource("C:\video\noisy.avi")
Y1 = ConvertToYUY2(Orig)

Sclip = TemporalCleaner(Y1, 4, 6)
Mask = Levels(Sclip,16,0.7,150,16,255,coring=false)  # black where smoothing should happen
#Greyscale(Mask)  # useful for viewing Mask to judge threshold setting

# Overlay (clip, clip overlay, int ''x'', int ''y'', clip ''mask'', float ''opacity'', string ''mode'', bool ''greymask'', string ''output'', bool ''ignore_conditional'', bool ''pc_range'')

Overlay(Sclip, Y1, 0,0, Mask)  # darker areas in Mask make Y1 more transparent & replaced by Sclip filtered pixels


#===========================================================

# ConverttoYV12()
# Histogram(mode="levels")  # Hist() requires YV12 format

# ColorYUV(levels="PC->TV") # just in case this is needed


# === below are misc. notes for other noise reducing filters

# Trim(1800,0) # deletes the first n frames
# FluxSmooth([clip], int temporal_threshold, int spatial_threshold)
# FluxSmooth(10,5) is good for clean DV clips (VX2k)
# ConvertToYUY2(interlaced=true)
# SpatialSoften(clip clip, int radius, int luma_threshold, int chroma_threshold)
# TemporalSoften(clip clip, int radius, int luma_threshold, int chroma_threshold 
#   [, int scenechange] [, int mode]) 
# Good initial values: TemporalSoften(4,4,8,15,2)
# Sclip=  FluxSmooth(Y1,10,3)
# FluxSmooth(Y1,200,200)  # hugely exaggerated values
# TemporalCleaner (clip, int "ythresh", int "cthresh")