# AddGrain/AddGrainC

## Abstract

author: Tom Barry, Foxyshadis
version: 1.4
download: http://foxyshadis.slightlydark.com/random/AddGrainC.zip
category: Misc Plugins
requirements: YV12, YUY2, RGB Colorspace, SSE CPU

## Description

AddGrain generates film like grain or other effects (like rain) by adding random noise to a video clip. This noise may optionally be horizontally or vertically correlated to cause streaking.

### Usage

1) Place the AddGrain.dll in a directory somewhere. If that is the C:\Program Files\AviSynth 2.5\plugins folder folder (recommended) then you can omit the LoadPlugin command in your script. In your Avisynth file use commands similar to

    LoadPlugin("F:\AddGrain\AddGrainC.dll")
    AviSource("D:\wherever\myfile.avi")
    AddGrain(20, 0, 0)

Of course replace the file and directory names with your own.

### P arameters

`AddGrain` (float "var", float "hcorr", float "vcorr", float "uvar", int "seed")

`AddGrainC` (float "var", float "uvar", float "hcorr", float "vcorr", int "seed")

where:

var(1.0), uvar(0) = the standard deviation (strength) of the luma and chroma noise generated, 0 is disabled.
uvar does nothing in RGB mode.

hcorr(0), vcorr(0) = the horizontal and vertical correlation, which cause steaking effect. (0.0 to 1.0)

seed (-1) Specifies a repeatable grain sequence. Set to at least 0 to use.

constant (false) Specifies a constant grain pattern on every frame.

The correlation factors are actually just implemented as exponential smoothing which give a weird side affect that I did not attempt to adjust. But this means that as you increase either corr factor you will have to also increase the stddev (grain amount) in order to get the same visible amount of grain, since it is being smooth out a bit.

Increase both corr factors can somewhat give clumps, or larger grain size.

And there is an interesting effect with, say, AddGrain(800,0,.9) or any huge amount of strongly vertical grain. It can make any scene look like it is raining.

### Version History

`1.0 2003/06/18 Tom Barry Initial Release
1.1 2006/06/01 Foxyshadis Chroma grain + constant seed
1.2 2006/06/06 Foxyshadis Supports YUY2, RGB. Fix cache mess.
1.3 2006/06/10 Foxyshadis Crashfix, noisegen optimization
1.4 2006/08/11 Foxyshadis Constant replaces seed, seed repeatable
`

`$Date: 2006/09/17 20:03:08 $`