Internal functions/Runtime functions - Revision history

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Gzarkadas at 20:40, 15 February 2008

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== 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 '''<tt>last</tt>''' clip (the one that is passed to the runtime filter). Thus, first parameter doesn't have to be specified; it is replaced by the <tt>last</tt> clip.

* {{ScriptFunction|AverageLuma|v2.x|AverageLuma(clip)}}
* {{ScriptFunction|AverageChromaU|v2.x|AverageChromaU(clip)}}
* {{ScriptFunction|AverageChromaV|v2.x|AverageChromaV(clip)}}
: This group of functions return a float value with the average pixel value of a plane (Luma, U-chroma and V-chroma, respectively). They require that <tt>clip</tt> is in [[YV12]] [[Color_spaces|colorspace]] and [[ISSE]].
: ''Examples:''
threshold = 55
luma = AverageLuma()
luma < threshold ? [[Levels]](0, 1.0 + 0.5*(threshold - luma)/threshold, 255, 10, 255) : last

* {{ScriptFunction|RGBDifference|v2.x|RGBDifference(clip1, clip2)}}
* {{ScriptFunction|LumaDifference|v2.x|LumaDifference(clip1, clip2)}}
* {{ScriptFunction|ChromaUDifference|v2.x|ChromaUDifference(clip1, clip2)}}
* {{ScriptFunction|ChromaVDifference|v2.x|ChromaVDifference(clip1, clip2)}}
: This group of functions return a float value between 0 and 255 of the absolute difference between two planes (that is two frames from two different clips). Either the combined RGB difference or the Luma, U-chroma or V-chroma differences, respectively. They require that <tt>clip</tt> is in [[YV12]] [[Color_spaces|colorspace]] and [[ISSE]].
: ''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)
...

The next two groups of functions should be quite handy for detecting scene change transitions:

* {{ScriptFunction|RGBDifferenceFromPrevious|v2.x|RGBDifferenceFromPrevious(clip)}}
* {{ScriptFunction|YDifferenceFromPrevious|v2.x|YDifferenceFromPrevious(clip)}}
* {{ScriptFunction|UDifferenceFromPrevious|v2.x|UDifferenceFromPrevious(clip)}}
* {{ScriptFunction|VDifferenceFromPrevious|v2.x|VDifferenceFromPrevious(clip)}}
: This group of functions return the absolute difference of pixel value between the current and previous frame of <tt>clip</tt>. Either the combined RGB difference or the Luma, U-chroma or V-chroma differences, respectively.
: ''Examples:''
scene_change = YDifferenceFromPrevious() > threshold ? true : false
scene_change ? some_filter(...) : another_filter(...)

* {{ScriptFunction|RGBDifferenceToNext|v2.x|RGBDifferenceToNext(clip)}}
* {{ScriptFunction|YDifferenceToNext|v2.x|YDifferenceToNext(clip)}}
* {{ScriptFunction|UDifferenceToNext|v2.x|UDifferenceToNext(clip)}}
* {{ScriptFunction|VDifferenceToNext|v2.x|VDifferenceToNext(clip)}}
: This group of functions return the absolute difference of pixel value between the current and next frame of <tt>clip</tt>. Either the combined RGB difference or the Luma, U-chroma or V-chroma differences, respectively.
: ''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(...)

* {{ScriptFunction|YPlaneMax|v2.x|YPlaneMax(clip, float threshold)}}
* {{ScriptFunction|UPlaneMax|v2.x|UPlaneMax(clip, float threshold)}}
* {{ScriptFunction|VPlaneMax|v2.x|VPlaneMax(clip, float threshold)}}
* {{ScriptFunction|YPlaneMin|v2.x|YPlaneMin(clip, float threshold)}}
* {{ScriptFunction|UPlaneMin|v2.x|UPlaneMin(clip, float threshold)}}
* {{ScriptFunction|VPlaneMin|v2.x|VPlaneMin(clip, float threshold)}}
* {{ScriptFunction|YPlaneMedian|v2.x|YPlaneMedian(clip)}}
* {{ScriptFunction|UPlaneMedian|v2.x|UPlaneMedian(clip)}}
* {{ScriptFunction|VPlaneMedian|v2.x|VPlaneMedian(clip)}}
* {{ScriptFunction|YPlaneMinMaxDifference|v2.x|YPlaneMinMaxDifference(clip, float threshold)}}
* {{ScriptFunction|UPlaneMinMaxDifference|v2.x|UPlaneMinMaxDifference(clip, float threshold)}}
* {{ScriptFunction|VPlaneMinMaxDifference|v2.x|VPlaneMinMaxDifference(clip, float threshold)}}
: This group of functions return statistics about the distribution of pixel values on a plane (Luma, U-chroma and V-chroma, respectively). The statistics are, in order of presentation: maximum, minimum, median and range (maximum - minimum difference).
: <tt>threshold</tt> is a percentage, stating how many percent of the pixels are allowed above or below minimum. The threshold is optional and defaults to 0.
: ''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)

----
Back to [[Internal functions]].

[[Category:AviSynth_Syntax]]
[[Category:Scripting_Basics]]

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-== Runtime functions ==
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 [[Category:AviSynth_Syntax]]
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