ShowFilterLumaEffect

[fvisagie]

Hi All,

Here's a utility for displaying the effect of a specified filter on clip luma to look for clipping and/or banding. It displays the filtered clip and histogram on the right alongside the original clip and histogram on the left. It's useful for testing whether a specific filter would cause clipping or banding of the current luma range, and for visualising luma normalisation and/or dithering settings.

http://forum.doom9.org/attachment.php?attachmentid=13342&d=1363294153

The display is actually jagabo's idea (http://forum.videohelp.com/threads/354292-Preparing-this-Rec-601-YV12-clip-for-Rec-709-MPEG-2-encoding?p=2226253&viewfull=1#post2226253). I just wrapped it in a function and parameterised the filter for convenient testing.

Updated to 1.1.0 - added identifying subtitles on top

#-------------------------------------------
# ShowFilterLumaEffect 1.1.0
# Visualises effect of specified filter on clip luma, with specific emphasis on clipping and/or banding
# - displays the filtered clip and histogram alongside the original clip and histogram
#
# Useful when
#
# Testing whether specified filter or function would cause clipping or banding of current luma range
# - this is useful when one intends to do initial filtering before normalising the luma range
# Normalising clip luma range (provide normalising filter or function as input to the function for visualising results)
# Dithering colour banding (provide dithering filter or function as input to the function for visualising results)
#
# ShowFilterLumaEffect(clip c, string filter)
#
# <c> input clip
# <filter> filter expressed in OOP notation
#
# Usage
#
# # Testing whether specific filter would cause clipping or banding of current luma range
# ShowFilterLumaEffect(OpenDMLSource("DV encode test source.avi"), """QTGMC(Preset="Slower").Crop(0, 8, -10, 0).Spline64Resize(720, 576)""")
# # Visualising effect of normalising, dithering, etc.
# ShowFilterLumaEffect(OpenDMLSource("DV encode test source.avi"), "levels(0, 1.0, 255, 2, 235, coring=false)")
#
# Requirements
#
# input clip must meet specified filter's criteria
# filter parameter must be provided in OOP notation
#
# Version history
#
# 1.1.0 Francois Visagie
# added identifying subtitles
#
# 1.0.0 Francois Visagie
#

function ShowFilterLumaEffect(clip c, string filter) {
original = c
filtered = Eval("original." + filter)
orghisto = original.Histogram(mode="classic").Crop(original.Width(), 0, 0, 0).TurnLeft()
orghisto = orghisto.Spline64Resize(original.Width(), orghisto.Height())
filhisto = filtered.Histogram(mode="classic").Crop(filtered.Width(), 0, 0, 0).TurnLeft()
filhisto = filhisto.Spline64Resize(filtered.Width(), filhisto.Height())
return(StackHorizontal(StackVertical(orghisto, original.Subtitle("original", align=1)), StackVertical(filhisto, filtered.Subtitle(filter, align=1))))
}
I hope you find it useful. Feel free to post any comments or improvements.

Cheers,
Francois