Noise Reduction Suite (NRS) Filter for VirtualDub
NRS is designed to reduce differencies across frames (for better
compression) and to cut out noise near frame borders. The filter provides
two main areas of functionality: dynamic noise reduction and cropping/shifting.
The luminance functionality operates as follows:
The important thing is how the thresholds are determined from the
luminance of the new pixel. Human eyes are more sensitive in dark areas,
so different thresholds are used according to the luminance of the pixels.
And since the eyes are sensible to luminance changes in a logarithmic way
the luminance range is split into 8 pieces and thresholds distributed along
these pieces. To see how the thresholds are distributed, look at
the "Luminance=Threshold" labels.
- The old and new pixels are averaged (blended).
- The luminance of the new pixel is calculated and
determines a threshold.
- If the absolute value of the difference between
the blended pixel and the old pixel exceeds the
threshold, then the unchanged new pixel is used;
otherwise the blended pixel is used.
The cropping/shift functionality allows for cropping from any frame border(s),
automatically centering the resulting area in the original frame size, and
shifting the area as desired.
Version 1.4 [Source code]
Version 1.4 adds the ability to be imported into Avisynth.
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