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.



The display is actually jagabo's idea. 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