MaskTools v1

Abstract

Table of contents

• Introduction
• Filters list
• Filters description
• Changelog

I) Introduction

AnisoTools's dll contains a set of filters articulated around a filtering idea named anisotropic filtering. Anisotropic filtering is a recursive filtering technic that uses local gradient values into an iterative formula in order to achieve the goal of the filtering. It can be use for various purposes, such as denoising, sharpening, inpainting, etc...

II) Filters list

• Denoising :
  • at_denoise : denoise the video spatio temporally.

III) Filters description

at_denoise

at_denoise : float sstep(0.8f), float tstep(0.8f), float edge(1.0f), float edgey, float edgeu, float edgev, float motion(1.0f), float motionv, float motionv, float motionv, int iterations(5), int center(4), string fedge("0 x edge / abs - exp"), string fedgey, string fedgeu, string fedgev, string fmotion("0 x motion / abs - exp"), string fmotiony, string fmotionu, string fmotionv

• at_denoise is a spatio-temporal mo-comped anisotropic denoiser. It is quite versatile, allowing at the same time both strong denoising and yet no edge blurring.
• sstep defines the amount of spatial filtering applied at each iteration of the algorithm. Too high values (that is, values over 1.0) will result in unstable filtering (you shouldn't want that). Too low values ("too low" depends on other settings) will result in the filter not filtering spatially (since internal computations are made with limited precision). Values inbetween should be fine. Small steps are theorically better but may require too much iterations to achieve the wanted level of filtering, and the limited precision might have unwanted side effect with small values anyway.
• tstep defines the amount of temporal filtering applied at each iterations of the algorithm. All other comments about sstep applies.
• edge controls the edge protection. The lower, the better protected the edges will be. Of course, setting it too low will result in the filter mistaking any noise pixel for an edge (thus filtering nothing spatially). Too big values, however, will make the filter completely edge-unaware, thus transforming it into a slow & dumb spatial blur (quite like a recursive Blur()).
• edgey/u/v, if defined, allows to specify a different edge value for each luma and chroma planes.
• motion controls the motion protection. The lower, the better protected against false motion the filter will be. Set too low, it will disable temporal filtering. Too high will create blocking artifacts that come from block-based motion compensation, and ghosting.
• motiony/u/v, if defined, allows to specify a different edge value for each luma and chroma planes.
• iterations is number of iterations for the algorithm. The bigger, the better and the slower (speed is inversely proportionnal to the number of iterations). There's a threshold over which you won't see any differences, and that threshold should be the value to be used. The lower the step, the bigger the needed number of iterations for reaching stability will be.
• center controls the computation of local spatial gradients. Those gradients are computed on a blurred version of the frame, to make gradient a bit less sensitive to noise. The bigger, the less blurred the frame will be. Minimum value is 1.
• fedge defines the formula used to protect the edges. It's a reverse polish expression, in which "edge" is replaced by edge, while "x" is replaced by the local directionnal gradient (and thus can be negative, ranging from -255 to 255).
• fedgey/u/v allows to define a specific edge formula for each planes.
• fmotion defines the formula used to protect against temporal artifacts. It's a reverse polish expression, in which "motion" is replaced by motion, and "x" by the local temporal gradient along the motion compensation (it can be negative, ranging from -255 to 255).
• fmotiony/u/v allows to define a specific motion formula for each planes.

IV) Changelog

Alpha 3 :

• added : proper documentation (avisynth's style)
• added : per plane specific parameters
• added : edge and motion protection formulas.
• fixed : support for edge = 0 or motion = 0.

Alpha 2 :

• renamed : at_spatial into at_denoise
• changed : parameters influence for at_denoise
• added : temporal denoising
• added : motion compensated temporal denoising
• added : resolution restriction to mod 16 horizontally & vertically

Alpha 1 :

• Initial release.