TComb

Latest revision as of 19:02, 24 February 2021

[edit] Description

TComb is a temporal comb filter (it reduces cross-luminance (dot crawl) and cross-chrominance (rainbows) artifacts in static areas of the picture). It will ONLY work with NTSC material, and WILL NOT work with telecined material where the rainbowing/dotcrawl was introduced prior to the telecine process! It must be used before IVTC or deinterlace in order to work. In terms of what it does it is similar to GuavaComb/DeDot.

TComb does support seeking... that is, jumping to a random frame will produce the same result as if you had linearly run up to that frame. For dot crawl removal TComb requires at least 3 static fields of the same parity and for rainbow removal TComb requires at least 5 static fields of the same parity.

[edit] Requirements

• [x86]: AviSynth+ or AviSynth 2.6
• [x64]: AviSynth+
• Supported color formats: Y8, YV12, YV16, YV24, YV411, YUY2

• Microsoft Visual C++ 2019 Redistributable Package (x86 / x64)

*** vc_redist.x86.exe is required for TComb-x86

*** vc_redist.x64.exe is required for TComb-x64

[edit] Syntax and Parameters

TComb (clip, int "mode", int "fthreshL", int "fthreshC", int "othreshL", int "othreshC", bool "map", float "scthresh", bool "debug", int "opt")

clip   =

Input clip.

int  mode = 2

Controls whether both luma/chroma are processed or only one or the other.

Possible settings:

• 0 - process luma only (dot crawl removal)
• 1 - process chroma only (rainbow removal)
• 2 - process both

int  fthreshL = 4

int  fthreshC = 5

Filtered pixel correlation thresholds.

One of the things TComb checks for is correlation between filtered values over the length of the filtering window. If all values differ by less than fthreshL (for luma) or fthreshC (for chroma) then the filtered values are considered to be correlated.

Larger values will allow more filtering (will be more effective at removing rainbowing/dot crawl), but will also create more artifacts.

Smaller values will produce less artifacts, but will be less effective in removing rainbowing/dot crawl. A good range of values is between 4 and 7.

int  othreshL = 5

int  othreshC = 6

Original pixel correlation thresholds.

One of the things TComb checks for is correlation between original pixel values from every other field of the same parity. Due to the oscillation period, these values should be equal or very similar in static areas containing dot crawl or rainbowing.

If the pixel values differ by less than othreshL (for luma) or othreshC (for chroma) then the pixels are considered to be correlated.

Larger values will allow more filtering (will be more effective at removing rainbowing/dotcrawl), but will also create more artifacts.

Smaller values will produce less artifacts, but will be less effective in removing rainbowing/dotcrawl. A good range of values is between 4 and 8.

bool  map = false

Identifies pixels that are being replaced with filtered values.

Each pixel in the output frame will have one of the following values indicating how it is being filtered:

0 - not being filtered

85 - [1 2 1] average of (n,n+1,n+2)

170 - [1 2 1] average of (n-2,n-1,n)

255 - [1 2 1] average of (n-1,n,n+1)

** n = current frame

float  scthresh = 12.0

Scenechange threshold; sets the scenechange detection threshold as a percentage of maximum change on the luma plane.

Use the debug output to see which frames are detected as scenechanges and the scenechange statistics.

bool  debug = false

Will enable debug output. The only thing it shows are the scenechange stats.

The info is output via OutputDebugString(). You can use the utility "DebugView" from sysinternals to view the output.

The frame numbers in the debug output correspond to the input clip after a SeparateFields() call. TComb internally invokes SeparateFields() before itself and weave() after itself.

int  opt = -1

Controls which cpu optimizations are used.

Possible settings:

• 0 - use C routines
• other - automatically choose SSE2 or C

[edit] Basic Setup/Usage

Setting up TComb is pretty simple. The only values that would ever really need adjusting are fthreshL/fthreshC, othreshL/othreshC, and mode.

Set mode to 0 if you want to do dot crawl removal only, set it to 1 if you want to do rainbow removal only, or set it to 2 to do both.

Dot Crawl Removal Tweaking (fthreshL/othreshL):
To find good values for fthreshL/othreshL, start with the following line:

TComb(mode=0, fthreshL=255, othreshL=255)

Now, keep othreshL at 255 but set fthreshL down to 1. Keep increasing fthreshL in steps of 1 to 2 until you find the point at which all dot crawl is removed. Remember that value.
Next, set fthreshL back to 255, and set othreshL to 1. Now, increase othreshL in steps of 1 or 2 until you find the point at which all dot crawl is removed. You've now got values for fthreshL/othreshL.

Rainbowing Removal Tweaking (fthreshC/othreshC):
To find good values for fthreshC/othreshC, start with the following line:

TComb(mode=1, fthreshC=255, othreshC=255)

Now, keep othreshC at 255 but set fthreshC down to 1. Keep increasing fthreshC in steps of 1 to 2 until you find the point at which all (or most) rainbowing is removed. Remember that value.
Next, set fthreshC back to 255, and set othreshC to 1. Now, increase othreshC in steps of 1 or 2 until you find the point at which all (or most) rainbowing is removed. You've now got values for fthreshC/othreshC.

Once you've got values for mode, fthreshL/fthreshC, and othreshL/othreshC, add the necessary TComb() line into your script and run through part of it. If you see any artifacts try lowering your fthresh/othresh values.

[edit] Changelog

v2.3 (20210224 pinterf)
   Y8, YV16, YV24, YV411 support

v2.2 (20210223 - pinterf)
   Fix: unsave register x64 assembler causing artifacts
   Drop all external asm
   Rewrite assembler in SIMD intrinsics (old stuff is not removed yet, only conditionally ignored)
   Add CMake build system
   Add MinGW/gcc support
   Add linux support (with ENABLE_INTEL_SIMD=off option as well)
   Add build instructions to README.md

v2.1 (20210221 - pinterf)
   project forked to https://github.com/pinterf/TComb/
   param 'opt' is back for debug. 0 means pure C code
   Fix bug in x64 assembler buildFinalMask_SSE2
   Fix crash in 32bit version of VerticalBlur3_SSE2
   Fix: scenechange SSE2 did not work
   Fix: x64 assembler HorizontalBlur6_SSE2
   Fix: HorizontalBlur6: C only did top 2 lines. SSE2 bad top 2 lines
   Fix: HorizontalBlur3_SSE2 artifacts (both x86 and x64)
   Fix: HorizontalBlur3_SSE2 missing rounder (both x86 and x64)
   (now C and SSE2 is giving identical results)
   Code:
       Update to Visual Studio 2019
       update to actual Avisynth+ headers
       clang-friendly code
       removed memcpy and bitblt variants
       replaced planarframes module with the one I updated in tivtc project for Avisynth+ and hbd preparation
       Fix debug build configuration in VS project settings

07/26/2015  v2.0.0.1 (Elegant996)
    + Corrected the masks used in HorizontalBlur6 for x64.

07/17/2015  v2.0 (Elegant996)
    * project moved to https://github.com/Elegant996/TComb/
    + Removed buffering of frames/info that weren't actually used (was there for
      development/testing purposes). Should save a lot of RAM usage.
    + Switched to AVS 2.6 API since AviSynth 2.6.0 was released.
    + Added x64 support which also utilizes SSE2. This also includes some missing
      SSE2 functions (andNeighborsInPlace_SSE2).
    + Restructured debug and error messages so that it was apparent that TComb was responsible.
    - Removed MMX/ISSE support as times have changed and the support was not going to be carried over to x64.
    - Removed "opt" parameter. TComb will now use SSE2 if available and will fallback
      on C++ if it is not supported.

05/16/2006  v2.0 Beta 2
    + Stricter checking of othreshL/othreshC when looking for oscillation
    + For dot crawl detection require at least one vertical neighbor (y-1/y+1, x-1/x/x+1)
    - fixed possible crash with yuy2 input (sse2 planar<->packed conversions)

03/31/2006  v2.0 Beta 1
    - complete rewrite

06/24/2005  v0.9.0
    - Initial Release

[edit] Archived Downloads

[edit] External Links

• Scintilla's Guide - Additional usage information mainly for dot crawl.
• GitHub - Source code repository (v2.0 - Elegant996)
• GitHub - Source code repository (v2.1 - pinterf)

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