DeNoise

Author V. C. Mohan
Date Aug 2014
EMail: mohanvc

DeNoise plugins for Avisynth 2.5 and 2.6 versions, are free and the author does not give any guarentee for its operation. It may be downloaded and used at the users risk.

This is an adaptive local noise reduction filter. It uses global variance of the noise, local mean and local variance in a moving grid of specified size. It tries to preserve edges as closely as possible. The global variance value can be specified or it can be computed from a window. The global variance can have one value for the entire clip or can vary frame to frame linearly or computed from a window with its coordinates linearly moving with frame numbers .

version 2.5 plugin works in YUY2, YV12, RGB32 and RGB24 color spaces. version 2.6 plugin works in YUY2, Planar, RGB32 and RGB24 color spaces. In case of YUY2 or planar formats limiting process to luma ( Y) only exists. Option to use Y plane variance for U and V planes exists, however, (as the variance values in a table below shows them to be dissimilar) it may not be good idea to do so

The window for computing global variance should be located in an area with least image grey level variations, so that noise statistic is correctly estimated. Note that this window coordinates must be specified as default values are not provided

The process tries to retain the sharpness of the image, though some blurring may be unavoidable. The process may be repeated number of times to get desired result. However results depend on window selected.

Details of parameters
Description	Name	Type	Limits	Default
Input clip		clip		none
Starting frame number to process	sf	integer	within clip	0
End frame number to process	ef	integer	within clip and not less than sf	last frame
Number of pixels along x axis in moving grid	xgrid	integer	3 to 9	5
Number of pixels along y axis in moving grid	ygrid	integer	3 to 9	xgrid
Is Global variance to be computed?	getvar	boolean	true for yes, false for is specified	true
Is variance valid for all clip or only frame	clip	boolean	true for yes, false for frame	true
window left x at start frame for computing global variance	lx	integer	within clip, less than rx	none. Must be specified
window top y at start frame for computing global variance	ty	integer	within clip, less than by	none. Must be specified
window right x at start frame for computing global variance	rx	integer	within clip, more than lx	none. Must be specified
window bottom y at start frame for computing global variance	by	integer	within clip, more than ty	none. Must be specified
window left x at end frame for computing global variance	elx	integer	within clip, less than erx	lx
window top y at end frame for computing global variance	ety	integer	within clip, less than eby	ty
window right x at end frame for computing global variance	erx	integer	within clip, more than elx	rx
window bottom y at end frame for computing global variance	eby	integer	within clip, more than ety	by
Variance specified at start frame	var	int	>0	100
Variance at end frame	evar	int	>0	var
Whether U and V of YUY2 and YV12 formats to be denoised	uv	boolean	true for uv process, false for not process	true
Whether variance of Y to be used for u and v also	usey	boolean	true yes, false no	false
Whether variance values are to be displayed as an error message	show	boolean	true yes, false no	false

Usage examples
Denoise()
DeNoise(a,35,55,clip=false,lx=220,rx=245,ty=322,by=402)
DENOISE(d,getvar=false,var=120,evar=160,xgrid=5,ygrid=7)
On top input, center is Output and at bottom noise removed example

following script used to get the images below:


denoise(img1, lx = 350, rx = 390, ty=460,by=560,uv = true, usey = false)

On left is input, middle is with 2 iterations, right is with 4 iterations

Left 6 iterations, middle 8 iterations, right 10 iterations

The variance values within the specified window after each iteration of the above example is given in the table below.

iter no	rgb red	rgb green	rgb blue	yuy2 y	yuy2 u	yuy2 v	yv12 y	yv12 u	yv12 v
0	116	76	174	61	8	22	61	8	22
1	42	20	98	16	6	19	16	6	19
2	31	14	91	12	5	18	12	4	18
3	28	11	89	9	5	17	9	4	17
4	25	9	88	9	4	17	9	4	17
5	24	9	88	8	4	17	8	3	16
6	22	8	88	8	4	17	8	4	16
7	21	8	88	7	3	17	7	3	15
8	20	7	88	7	4	17	7	3	15
9	19	8	89	7	3	18	7	3	16
10	19	8	89	7	3	18	7	3	16

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