BlindDeHalo3

Abstract
Author	Didée
Version	3
Download	Dehalo
Category	YV12
Requirements
License
Discussion

Introduction

Filter to remove edge enhancement artefacts.

Required Filters

• MaskTools2 2.0a48+
• RemoveGrain

Parameters

BlindDeHalo3(clip clp, float "rx", float "ry", int "strength", float "lodamp", float "hidamp", float "sharpness", float "tweaker", int "PPmode", int "PPlimit", bool "interlaced")

rx, ry float = 3.0

The radii to use for the [quasi-] gaussian blur, on which the halo removal is based.

strength int = 125

The overall strength of the halo removal effect.

lodamp, hidamp float = 0.0

Range: 0.0 - ??? (try 4.0 as a start)

With these two values, one can reduce the basic effect on areas that would change only little anyway (lodamp),

and/or on areas that would change very much (hidamp).

Lodamp does a reasonable job in keeping more detail in affected areas.

Hidamp is intended to keep rather small areas that are very bright or very dark from getting processed too strong.

Works OK on sources that contain only weak haloing - for sources ::with strong oversharpening, it should not be used, mostly.

(Usage has zero impact on speed.)

sharpness float = 0.0

Range: 0.0 - 1.58

By setting this bigger than 0.0, the affected areas will come out with better sharpness.

However, strength must be chosen somewhat bigger as well, then, to get the same effect than without.

(This is the same as initial version's "maskblur" option.)

tweaker float = 0.0

Range: 0.0 - 1.00

May be used to get a stronger effect, seperately from altering "strenght".

(Also in accordance to initial version's working methodology. I had no better idea for naming this parameter.)

interlaced bool = false

As formerly, this is intended for sources that were originally interlaced, but then made progressive by deinterlacing.

It aims in particular at clips that made their way through Restore24.

PPmode int = 0

When set to "1" or "2", a second cleaning operation after the basic halo removal is done. This deals with:

a) Removing/reducing those corona lines that sometimes are left over by BlindDeHalo

b) Improving on mosquito noise, if some is present.

PPmode=1 uses a simple gaussian blur for post-cleaning.

PPmode=2 uses a 3*3 average, with zero weigthing of the center pixel.

Also, PPmode can be "-1" or "-2". In this case, the main dehaloing step is completely discarded, and *only* the PP cleaning is done.

This has less effect on halos, but can deal for sources containing more mosquito noise than halos.

PPlimit int = 0

Can be used to make the PP routine change no pixel by more than [PPlimit].

I'm not sure if this makes much sense in this context. However the option is there - you never know what it might be good for.

Comments & Tips

Additional information for optimal usage. Written by Didée in this thread.

• Regarding "strength" & "sharpness" & "tweaker"

These three behave somewhat similar, but not the same.

A bigger value for "sharpness" is similar to reducing "strength".

A bigger value for "tweaker" is similar to increasing "strength" value -- and vice versa for both.

Also the other way round: when increasing "sharpness", you probably have to increase "strength" a little as well, to get the same removal effect.

Usage of "sharpness" works in particular good when bigger radii (say, >2.5) are used for dehaloing.

Usage of "tweaker" is more useful when working with sources containing thin, weak halos.

In the end, it comes down again to trial & error.

• Lodamp and Hidamp

Technically, these two are the "n" constants in two scaling factors of the form "x/(x+n)",

which are used when creating a LUT from the difference between input clip and its gaussian blurred version.

As described above, "lodamp" deals for better protection of areas where this difference is alredy small.

Effectively, it preserves some more of weak detail in areas of high contrast.

A value of 4.0 seems a good starting point.

One can also try to use bigger values like 16.0 or so, along with a bigger "strength" value.

By this, one can somewhat change the characteristics of "what-is-processed-how-strongly".

"hidamp" tries to do the opposite: protect small detail that is very bright or very dark from being toned down too much.

But its usability is much more restricted: it seems to work OK when the actual halos of the source are rather weak,

and/or when not too small radii are used - in this case, the protection of very prominent detail works out, mostly.

In case the source contains strong haloing, is's better to not use "hidamp" at all:

in this case, the halos itself would be considerd to be "prominent detail" and be protected ... no go.

Examples

Full function call with default values:

AviSource("Blah.avi")
BlindDeHalo3( rx=3.0, ry=3.0, strength=125, 
\            lodamp=0.0, hidamp=0.0, sharpness=0.0, tweaker=0.0,
\            PPmode=0, PPlimit=0, interlaced=false)