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DeScratch

The descratch video plugin can be used to remove vertical scratches from film. It can also be used, after image rotation, to remove horizontal noise lines that may appear on analog VHS captures. For best results YUV should be the video format; however if your format is RGB, it will first be converted to YUV. There are many tuneable parameters necessary to get good results for your specific film.

Figure 10.41 shows a list of the parameter descriptions:

Figure 10.41: DeScratch control window

Figure 10.42: Various parameters of DeScratch

threshold
  instantaneous slope value; chroma difference in numerical pixels.
asymmetry
  maximum asymmetry of surrounding pixels.
Mode
  None; Low=black; High=white; All=both; y – processing mode for luma plane; u– processing mode for chroma u plane; v – processing mode for chroma v plane.
width min/max
  minimal scratch width in pixels and maximum scratch width in pixels.
len min/max
  percent minimal scratch length and percent maximum scratch length.
len blur
  scaled radius of vertical blur for frame analysis.
len gap
  number of pixels for maximum vertical gap to be closed.
max angle
  maximal angle to vertical in degrees.
fade
  percent of how much it fades to and how much it. Uses between before image and blurry image.
border
  pixel thickness of border near scratch for partial restoration.
Mark
  shows the potential scratch lines for ease of viewing and for debugging. It shows chosen pixels in the color green, close but still rejected in yellow, and extreme pixels in the color red. This makes it easy to vary some parameters to choose more or fewer scratch lines.
Reset
  activating this button returns all of the parameters to their default values.

Figure 10.43 shows a before and after DeScratch scenario. With Mark set, you can see the black lines which indicate what the program was looking at to determine the scratches to remove.

Figure 10.43: Original video with scratch; Option Mark selected and Final video