DeScratch - Scratches Removing Filter
Plugin for Avisynth 2.5
Version 0.5
July 31, 2004
Copyright (C)2003-2004 Alexander G. Balakhnin aka Fizick.
http://bag.hotmail.ru
This plugin removes vertical scratches from films.
Also it may be used for removing of horizontal noise lines such as drop-outs from analog VHS captures
(after rotation of image).
Examples
Old scratched 8 mm film. Top half frame - before filter , bottom half frame - after filter
How it works
The plugin firstly detects scratches, then removes its.
It works with every frame, uses spatial information only from current frame.
I adapt it to restoration of my old 8 mm films, may be it will be useful to
somebody else.
Scratch detecting
Apply some vertical blur to frame copy, for suppression of image thin
structure, inclined lines and noise.
Search for local extrems of pixel values in every row, with some threshold difference criterion.
Put these extrems to some map (frame).
Optional close vertical gaps in extrems by vertical expanding of extrems points.
Test extrems map with length and angle criterions, so select real scratches.
Scratch removing
Scratches may be either partially transparent, smooth (with image
details),
or opaque (with no details or almost destroyed).
In the first case, plugin can subtract smooth (blurred) part of scratch pixels
variation from original image. Therefore, image details are kept .
In the second case, plugin replaces scratched pixels by mean values of
some neighbours pixels (in same row).
We have also intermediate case by setting some percent of detail to keep.
The plugin have some adaptation of keeped value according to pixels
difference.
In all cases, some nearest neighbours may also partially changed for more
smoothing.
Needed software
The program is plugin (filter) for free Avisynth 2.5 (http://www.avisynth.org)
Tested with version 2.55beta (some versions have bug with Turnleft() !).
Filter is not more needed in Avisynth C Interface (avithynth_c.dll) by Kevin Atkinson.
Compiled with MS VC++ Toolkit 2003.
Sample script for Avisynth (used for sample clip above):
Avisource("input.avi")
loadplugin("descratch.dll")
converttoYV12()
descratch(mindif=2)
Plugin Parameters:
mindif - minimal difference of pixel value in scratch from neighbours pixels
for luma plane
(from 1 to
255, default 5):
maxgap - maximal vertical gap to be closed (from 0
to 255, default 3):
maxwidth - maximal scratch width ( fixed to
default=3 in current version)
minlen - minimal scratch length (default = 100)
maxangle - maximal angle to vertical (float in degrees,
default=5.0)
blurlen - radius of vertical blur for frame
analysis (default = 15)
keep - percent of scratch detail to keep (default
= 100)
border - thickness of border near scratch for
partial restoration (default=2)
modeY - processing mode for luma plane (0 -
no, 1 - low(black), 2 - high(white), 3 - both, default=1)
modeU - processing mode for chroma U plane (0 - no, 1 - low(green), 2 - high(red), 3 - both, default=0)
modeV - processing mode for chroma V plane (0 - no, 1 - low(yellow), 2 - high(blue), 3 - both, default=0)
mindifUV - minimal difference of pixel value in scratch from neighbours pixels
for chroma planes
(from 0 to
255, default 0):
if =0, then
internal mindifUV value is same as mindif .
mark - mark scratch in debug mode (true or false,
default =false)
( set
rejected extrems pixels to grey, set scratch pixels to lowest or highest values)
(maxgap, maxwidth, minlen, blurlen, border - in pixels.)
You MUST tune parameters for your video.
Use Avisynth commands Greyscale(), UtoY(), VtoY() , and."mark"
parameter for debug and tuning.
Horizontal noisy lines removing
Such long thin noisy lines sometimes appears in analog capture material (TV or VHS line drop-out, etc).
This problem was discussed at Doom9, see article Removal of clicks and scratches (July 10-31, 2004).
But in article DeSpot plugin was firstly used, what is not most appropriate tool for this, due to very weak noise level.
DeScratch could be more effective, however is not ideal too (old version can process only luma plane).
Of course, you must rotate clip for processing with Descratch (and do not forget to rotate it in reverse direction after cleaning :-).
See results for some VHS source (from Ivo).
Top half frame - before processing , bottom half frame - after processing:
Script used for example clip (with optimal Descratch parameters - big minlen, null maxangle):
loadplugin("descratch.dll")
Avisource("drop-outs_.avi")
converttoYV12()
crop(0,0,-0,288) # select top part of frame to save screen space
input=last
assumetff()
separatefields() # for analog interlaced source
turnleft()
descratch(mindif=4,maxgap=20,minlen=300,blurlen=50,keep=100,border=0,maxangle=0)
turnright()
weave() # restore fields
# Compare source frame and frame after scratch removing
StackVertical(input,last)
For color line dropouts removing, you may use modeU, modeV and mindifUV parameters.
License
This program is FREE software for non-commercial using, but WITHOUT ANY WARRANTY.
Please consider to make some donation.
Version changes log and downloads:
Version 0.5, July 31, 2004
fixed
read-write pointer bug,
add "mindifUV" parameter for
separate control of chroma U,V planes cleaning,
some code reorganization,
documentation
corrected.
Download
DeScratch version 0.5
Version 0.4, July 17, 2004
Added chroma processing: modeY, modeU, modeV parameters,
introduced in version 0.4 after Ivo's request (old versions can process luma only).
mindif is now positive only,
marked scratches value is not inverted but contrasted now.
Download
DeScratch version 0.4
Version 0.3, July 14, 2004 - ported
to native Avisynth plugin,
Speed increased due to fast blurring by Avisynth resizing functions.
Download
DeScratch version 0.3
version 0.2, 31 December 2003 - change to sharp extrems, add gaps closing
Download
DeScratch version 0.2
version 0.1, 22 December 2003 -
initial beta (not public)
Current version limitations:
Maximal scratch width is fixed to 3.
The plugin works only in YV12.