# Cnr2 (Chroma Noise Reducer)

## Abstract

author: Chroma Noise Reducer by MarcFD and others
version: 2.61
dowload: http://www.avisynth.org/warpenterprises/
category: Temporal Smoothers
requirements:

- YV12 & YUY2 Colorspace

## What it does

This filter is a Chroma Stabilizer for analogic sources.
It's a temporal filter and it's very effective against two chroma artifacts: stationary rainbows and huge analogic chroma activity.

## Usage

Add the following lines in your avisynth script :

LoadPlugin("Cnr2.dll") # example Cnr2() # for TV/VHS caps Cnr2("xxx", 4, 5, 255) # my suggestion to remove rainbows.

Syntax :

`Cnr2` (clip, mode="oxx", scdthr=8, ln=35, lm=192, un=47), um=255, vn=47, vm=255, log=false)

mode :

mode of each components, "YUV"
two modes are possible : wide ('o') and narrow ('x')
narrow mode is more sensible to variations, and less effective

scdthr :

scenechange detection threshold.
lower it to make scd more sensible.
if a scenechange is detected, cnr2 will
reset the filtering for the new scene

ln,lm,un,um,vn,vm : 0 to 255

the n values are the movement sensibility :
higher values will denoise more, but could produce ghosting artifacts
the m values are the maximum effectiveness of the denoiser :
lower them to reduce the denoising effect.

log :

to log scd internals. use DebugView to see it.

    > Cnr2()
    > Cnr2("oxx", 8, 35, 192, 47, 255, 47, 255, false)
    > Cnr2(mode="oxx", scdthr=8, ln=35, lm=192, un=47, um=255, vn=47, vm=255, false)

are three aliases : they would produce the same filtering.

## History

This Filter is inspired by the Virtual Dub filter Chroma Noise Reduction 1.1 (by Gilles Mouchard)
cnr 1.1 was a good chroma filter but was using YUV conversion to do is job.
I used it for VHS encodes, because it was the better Chroma Noise filter i tested
But when i started to use AviSynth and Huffyuv, RGB convertion was an overhead
So i take a look on the code and wrote my own filter from scratch, but based of the same algo.
the output of cnr2 is 99,9% to 100% the same as cnr (due to YUV colorspace)
and it's 3x-5x faster (Cnr2 can do real-time denoising in 640x480x25fps with a 1,4 Ghz CPU)

version 2.1 (31.7.2002)

little review. corrections.

version 2.2 (01.8.2002)

First frame bug fixed.

version 2.3 (17.11.2002)

YV12 Code and SCD (scene change detection)

version 2.4 (17.11.2002)

small changes/bug fixes

version 2.51 (13.11.2003)

Klaus Post: bug fixes.

version 2.6 (29.06.2004)

tritical: few bug fixes, scene change detection overhaul, code cleanup.

version 2.6.1 (30.06.2004)

tritical: made yuy2 processing fast again.

### Distribution :

This is a free sofware distribued under the terms of the GNU-GPL
The only restriction is to e-mail me if you want to do something with
the source because i don't want you to lose your time to decode my
cryptic C,C++,Delphi (or any other language) writing.
Thanks :)

### Contact :

Don't even doubt of e-mailing me for any suggestion :-), bug report :-(,
feature request :D, or whatever else :-P.
I hope you'll find this prog useful ! (i do...)

`$Date: 2005/10/03 16:49:04 $`