AviSynth Syntax - Runtime functions

These are the internal functions which are evaluated at every frame. They can be used inside the scripts passed to runtime filters (ConditionalFilter, ScriptClip, FrameEvaluate) to return information for a frame (usually the current one). When using these functions there is an implicit last clip (the one that is passed to the runtime filter). Thus, first parameter doesn't have to be specified; it is replaced by the last clip.

Average

AverageLuma(clip[, int offset = 0])
AverageChromaU(clip[, int offset = 0])
AverageChromaV(clip[, int offset = 0])
AverageR(clip[, int offset = 0])
AverageG(clip[, int offset = 0])
AverageB(clip[, int offset = 0])

This group of functions return a float value with the average pixel value of a plane (Luma, U-chroma and V-chroma, R, G or B respectively).

In v2.61 an offset argument is added which enables you to access other frames than the current one.

Examples:

ScriptClip(Last, """
    threshold = 55
    luma = AverageLuma ## gives the average luma of the current frame
    #luma = AverageLuma(1) ## gives the average luma of the next frame
    luma < threshold
    \ ? Levels(0, 1.0+0.5*(threshold-luma)/threshold, 255, 0, 255)
    \ : last
    Subtitle("luma=" + String(luma), align=2)
""")

Difference

RGBDifference(clip1, clip2)
LumaDifference(clip1, clip2)
ChromaUDifference(clip1, clip2)
ChromaVDifference(clip1, clip2)
RDifference(clip1, clip2)
GDifference(clip1, clip2)
BDifference(clip1, clip2)

Single-plane versions support only planar YUV or planar RGB clips. RGBDifference supports only packed (non-planar) RGB clips (that is RGB24/32/48/64).

This group of functions return a float value between 0 and 255 (or 0 and max_pixel_value for bit depths over 8) of the absolute difference between two planes from two different clips.

Either the combined RGB difference or the Luma, U-chroma or V-chroma, or R, B or B component differences, respectively.

Examples:

ovl = Overlay(last, mov_star, x=some_xvalue, y=some_yvalue, mask=mov_mask)
ldif = LumaDifference(ovl) # implicit last for clip1
udif = ChromaUDifference(Tweak(hue=24), ovl)
...

Difference from previous

The "Difference" function groups should be quite handy for detecting scene change transitions:

RGBDifferenceFromPrevious(clip)
LumaDifferenceFromPrevious(clip)
ChromaUDifferenceFromPrevious(clip)
ChromaVDifferenceFromPrevious(clip)
RDifferenceFromPrevious(clip1)
GDifferenceFromPrevious(clip1)
BDifferenceFromPrevious(clip1)

This group of functions return the absolute difference of pixel value between the current and previous frame of clip – either the combined RGB difference or the Luma, U-chroma, V-chroma or R, G, B differences, respectively.

Examples:

scene_change = (YDifferenceFromPrevious) > threshold)
scene_change ? some_filter(...) : another_filter(...)

Difference to next

RGBDifferenceToNext(clip[, int offset = 1])
LumaDifferenceToNext(clip[, int offset = 1])
ChromaUDifferenceToNext(clip[, int offset = 1])
ChromaVDifferenceToNext(clip[, int offset = 1])
RDifferenceToNext(clip[, int offset = 1])
GDifferenceToNext(clip[, int offset = 1])
BDifferenceToNext(clip[, int offset = 1])

This group of functions return the absolute difference of pixel value between the current and next frame of clip – either the combined RGB difference or the Luma, U-chroma, V-chroma, R, G or B differences, respectively.

In v2.61 an offset argument is added, which enables you to access the difference between the RGB, luma, chroma or R/G/B plane of the current frame and of any other frame.

Note that for example clip.RGBDifferenceToNext(-1) = clip.RGBDifferenceToPrevious, and clip.RGBDifferenceToNext(0) = 0.

Examples:

# both th1, th2 are positive thresholds; th1 is larger enough than th2
scene_change = (YDifferenceFromPrevious > th1) && (YDifferenceToNext < th2)
scene_change ? some_filter(...) : another_filter(...)

Color plane median, min, max, range

See also:

YPlaneMedian(clip[, int offset = 0])
UPlaneMedian(clip[, int offset = 0])
VPlaneMedian(clip[, int offset = 0])
RPlaneMedian(clip[, int offset = 0])
GPlaneMedian(clip[, int offset = 0])
BPlaneMedian(clip[, int offset = 0])

YPlaneMax(clip[, float threshold, int offset = 0])
UPlaneMax(clip[, float threshold, int offset = 0])
VPlaneMax(clip[, float threshold, int offset = 0])
RPlaneMax(clip[, float threshold, int offset = 0])
GPlaneMax(clip[, float threshold, int offset = 0])
BPlaneMax(clip[, float threshold, int offset = 0])

YPlaneMin(clip[, float threshold, int offset = 0])
UPlaneMin(clip[, float threshold, int offset = 0])
VPlaneMin(clip[, float threshold, int offset = 0])
RPlaneMin(clip[, float threshold, int offset = 0])
GPlaneMin(clip[, float threshold, int offset = 0])
BPlaneMin(clip[, float threshold, int offset = 0])

YPlaneMinMaxDifference(clip[, float threshold, int offset = 0])
UPlaneMinMaxDifference(clip[, float threshold, int offset = 0])
VPlaneMinMaxDifference(clip[, float threshold, int offset = 0])
RPlaneMinMaxDifference(clip[, float threshold, int offset = 0])
GPlaneMinMaxDifference(clip[, float threshold, int offset = 0])
BPlaneMinMaxDifference(clip[, float threshold, int offset = 0])

This group of functions return statistics about the distribution of pixel values on a plane (Luma, U-chroma, V-chroma, R, G and B respectively). The statistics are, in order of presentation: maximum, minimum, median and range (maximum - minimum difference).

Threshold is a percentage, stating how many percent of the pixels are allowed above or below minimum. The threshold is optional and defaults to 0.

In v2.61 an offset argument is added, which enables you to access the statistics of other frames than the current one.

The decision is based on creating a histogram on pixel values and counts then the given threshold is checked against this pixel level-pixel count table.

This histogram cannot be done for 32 bit float data thus 32 bit float pixels are converted to 16 bit integer data before creating the histogram.

Examples:

# median and average are close only on even distributions;
# this can be a useful diagnostic
have_intense_brights = YPlaneMedian() - AverageLuma() < threshold
...
# a simple per-frame normalizer to [16..235], CCIR, range
Levels(YPlaneMin(), 1.0, YPlaneMax(), 16, 235)

See more at Conditional filters section.

All-in-one stats

PlaneMinMaxStats(clip[, float threshold, int offset, int plane, bool setvar])

Returns an 6-element array with [min,max,thresholded minimum,thresholded maximum,median,average]

See more at Conditional filters section.

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Back to Internal functions.

Changelog

Version	Changes
Avisynth 3.7.2	Added a 6th element to PlaneMinMaxStats result
Avisynth 3.7.1	Added PlaneMinMaxStats
Avisynth+ pre2294	Added R, G, B versions of AverageXX, Min, Max, Difference and Median family.
AviSynth 2.61	added offset parameters

$Date: 2024/01/12 15:32:00 $