Virtual Dub Filters

Special filters

See a possible usage of these special filters on Avisynth Vertical Misalignment Zoom Correction pages about Stereoscopic Video by Gerrard M. Burnell

Interlaced RGB 0.3
Now with field conversion to grayscale !

Field Align 0.2

Field Shift 0.1

Restoration filters

Pops 0.1
This filter was built to remove or smooth pops, blots, spots, streaks and all kind of things that appear on old movie transcriptions.
This is a test version: it works well but it is not finished, please use conservative settings for testing as false spot detection can lead to errors on picture.
There are three parts to this: detection, correction and error bypassing.
It is based on the fact that this spots appear on only one frame and generally are either white or black.
Controls: Threshold (maximum delta level for zone inclusion), Black level (maximum luminance level on dark spot), White level (minimum luminance level on light spot), Color tolerance (maximum delta between RGB on spot), Maximum pop dimensions (width, height, global with backoff), Stability window (frames, 2 frames lag), Denoise and Debug.
On debug mode the pixels are coloured of red shades, green and white for detection levels debug, lines are inverted as they are excluded (bypassed), the frame is inverted for excess column detection or excess global detection (detection level is then halved and saved and acts as backoff for next frames).

Production filters

Frame Merger 0.1
This filter was built to smooth temporally the picture (blending each frame with the previous one) in order to reduce noise, artefacts and the bitrate needed to encode the stream. Blending strength and propagation are configurable.

Shadow Smoother 0.7
Spatial and temporal smoothing in the shadow areas of the picture.
Shadow Smoother version 0.7 corrects a bug with certain image widths.

Shadow Smoother Quick Cookbook !

* Start by selecting a threshold of 5/7, with strength as 1 and a difference of 2/3.

* Make a second pass and this time aim lower in the shadows but stronger with a threshold of 4/6, strength as 2/3 and a difference of 2/4.

* Difference of more than 4 tend to create artefacts with rough edges appearing on zones of transition. With high differences too much data can be kept from previous frames causing that, instead of reducing temporal noise (this noise is a compression reducer due to the increased data variation from frame to frame) it can introduce new noise thus creating sometimes visible artefacts.

* Keep temporal setting "pixel locking" and "noise locking" on as well as "post smoothing".

* Pixel locking occurs when difference between pixels on two frames (temporally) is roughly half of the configured maximum difference for temporal denoising. On normal temporal process the pixels are blended, on this special case the pixel from the previous frame is kept. This occurs only on the shadow area as by configured threshold.

* Noise locking is a special variation of pixel variation where if a pixel is horizontally sandwiched between two locked pixels then it becomes locked as well.

* Post smoothing enhances compression by applying a last step of horizontal smoothing (a strength 1 of "horizontal smoother") after temporal locking as a way of reducing high frequency components alien to the input material possibly created by the temporal process that would have a negative effect upon compression if they weren't smoothed.

* A third pass could be done over darker areas but this is normally not very productive.

* Warning: Threshold 8 is available and affects the entire picture which is normally not intended and causes a deep degradation of the perceived sharpness of the picture, keeping the smoothing to the darker areas of the pictures gives greater compression without sacrifying image quality so much. Reducing detail on shadows saves bitrate on areas where eye detail perception is physicaly reduced and on areas that are normally out of mind focus, so this can get very much unnoticed normally.

* After "shadow smoother", if your source is good and without noise you can apply a "Vertical Smoother" filter with strength 1, if by the contrary you have a noisy source you can go up to a 2/3 strength, reserving strength 4 to special occasions ...

Horizontal Smoother 0.1
Horizontal smoothing !

Vertical Smoother 0.3
Vertical smoothing ! Version 0.3 corrects a bug with certain image widths.

Valentim Batista 2003/04/01- timsara at softhome dot net