How to remove cross-luma
Info Cross-luma is an artifact caused by incomplete separation of the luma and chroma information in an analog video signal.
This results in typical diagonal needle-like artifacts at horizontal color edges. Sometimes a crossed pattern results.
Historically this artifact was caused by the way the color (chroma) information was added to the black&white TV signal in order to keep the new color TV signal compatible with existing b&w TV sets.
We filter out this artifact by looking for the typical structure in 3x3 pixel blocks at color edges which is characterized by large horizontal and vertical standard deviations.Settings Making the right settings can be a matter of trial and error.
There are two groups of settings: one for the detection of constant color and one for the detection of the cross-luma pattern in the non-constant color areas.
Actually the artifacts extend into the constant color area. This is what the "extent" setting is for.
You find more artifacts in the following way:However, relaxing the cross-luma detection may make the filter more abrasive.
- 1. Make conditions for "constant chroma" detection stricter
- longer test length
- longer min length
- smaller max chroma standard deviation
- 2. Enlarge extent
- 3. Relax conditions for the detection of cross-luma artifact in a 3x3 pixel block.
- lower minimum block standard deviation
- higher block maximum standard deviation
- larger percentage (not explained here)