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Author Dan Donovan
Version v0.51
Category Rainbow & Dot Crawl Removal
  • YV12
Discussion Closed source



Removes dot crawl, particularly in animated material.


  • AviSynth 2.5.8 or greater
  • Supported color formats: YV12

Syntax and Parameters

DeCrawl (clip, int "ythresht", int "ythreshs", int "cthresh", int "temporal", int "spatial", int "spatialpasses")

clip   =
Input clip.

int  ythresht = 7
Temporal luma threshold: the 2 temporally surrounding pixels must have a luma value within this threshold.
Range: 0 to 255

int  ythreshs = 8
Spatial luma threshold: the 2 vertically surrounding pixels must have a luma value within this threshold.
Range: 0 to 255

int  cthresh = 2
Chroma threshold: all 3 pixels must have a chroma value within this amount of each other.
Range: 0 to 255

int  temporal = 50
Temporal filtering: strength for temporal filtering. Set to 0 to disable.
Range: 0 to 100
  • Temporal filtering will replace each pixel with 50% of the current pixel (Yc) + 25% of the temporally previous pixel (Yp) + 25% of the next pixel (Yn), if:
    • Yc-Yp <= ythresht
    • Yc-Yn <= ythresht
    • Yp-Yn <= ythresht/8
    • chroma conditions are similar if enabled

int  spatial = 100
Spatial filtering: strength for spatial filtering. Set to 0 to disable.
Range: 0 to 100
  • Spatial filtering uses 1/2P(x,y) + 1/8P(x,y-1) + 1/8P(x,y+1) + 1/8P(x-w/376,y) + 1/8P(x+w/376,y), only taking into account the factors that are within the threshold. It does NOT cap those parameters to one threshold away.
    If a factor is not within the thresfield, the original pixel is substituted. Overall, it's not very destructive to most video as long as the threshold isn't set too high. You might want to use this two or three times in a row, but don't filter temporally at all past the first time.
  • Note: if a pixel is filtered temporally, it will not be filtered spatially.

int  spatialpasses = 1
Number of times to spatially filter, in case the effect is too weak for your source.
Range: 0 to 16


DeCrawl with default values:

DeCrawl(ythresht=7, ythreshs=8, cthresh=2, temporal=50, spatial=100, spatialpasses=1)


    - 0.51 - Minor speedup
    - 0.50 - Major speedup to chroma thresholding
    - 0.42 - Added spatialpasses
    - 0.41 - Bitblt chroma, thresholding tweaks, enable more compiler optimizations (note: 0.40+ are compiled w/ SSE)
    - 0.40 - Chroma for thresholding is now interpolated, chroma thresholding now affects spatial filtering, temporal thresholding slightly improved, defaults changed
    - 0.32 - slight optimizations, spatial filtering no longer takes precedence over temporal filtering
    - 0.31 - slight thresholding fix
    - 0.30 - Spatial filtering is now an adaptive convolution filter. See above...
    - 0.25 - Added basic 3-line spatial filtering. It doesn't work too well at the moment, though.
    - 0.20 - Major changes. This won't even seem like the same filter anymore. Don't set ythresh too high, though, ESPECIALLY if you use it on interlaced video.
             It may be used on interlaced video if you are careful.
    - 0.15 - Fixed a nasty bug (typo) with chroma checking...
    - 0.14 - I had ydiffthresh and ysamethresh reversed in the readme. Made filter more subtle, but still kicking ass on dot crawl.
    - 0.13 - Minor MMX optimization. Changed the averaging to average the current pixel and the 2 temporally surrounding pixels, instead of just the 2 surrounding.
    - 0.12 - HUGE bugfix making crashes quite often...
    - 0.11 - Added defaults (2,10,2)
    - 0.10 - Initial release

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