Anti-Dot Crawl

Common Options : Enabled, Disabled

 

Quick Review of Anti-Dot Crawl

Dot crawl is a visual artifact that plagues composite video signals (e.g. NTSC signals). Fortunately, it’s possible to greatly reduce dot crawl by using a comb filter.

The Anti-Dot Crawl BIOS feature controls the composite video decoder’s comb filter.

When enabled, the comb filter is enabled to suppress dot crawl artifacts.

When disabled, the comb filter is disabled and dot crawl artifacts are allow to manifest normally.

If you intend to play composite video signals on your system, it is highly recommended that you enable this BIOS feature to suppress dot crawl artifacts.

 

Details of Anti-Dot Crawl

Dot crawl is a visual artifact that plagues composite video signals (e.g. NTSC signals). The artifact appears as shimmering checkerboard or line patterns between contrasting colours. As the dots in the artifact crawl between those colours, that gave birth to the term “dot crawl”.

This visual artifact is due to crosstalk between the luminance (colourless) and chrominance (colour information) components of the composite video signal. As such, the only solution is to replace composite video signals with component video signals. Only by using separate component signals can such crosstalk be avoided completely.

Fortunately, it’s possible to greatly reduce dot crawl by using a comb filter. A comb filter is a phase cancellation filter that works by adding a slightly delayed version of the signal to the signal itself. It can be implemented in the composite video hardware or in software.

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The Anti-Dot Crawl BIOS feature controls the composite video decoder’s comb filter.

When enabled, the comb filter is enabled to suppress dot crawl artifacts.

When disabled, the comb filter is disabled and dot crawl artifacts are allow to manifest normally.

If you intend to play composite video signals on your system, it is highly recommended that you enable this BIOS feature to suppress dot crawl artifacts.

 

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