Composite video artifacts - what you need to know

In a composite video signal, the black & white component and the color components are combined into a single signal. In certain cases, information from the black & white signal will bleed into the color signal and vice versa. When the black & white signal bleeds into the color signal, the viewer sees colors where there shouldn't be any. This is shown in the image below. As the original video is completely black and white, the spurious color you see shouldn't be there.

When the color bleeds into the black and white signal, you may see crawling on edges of objects (not shown).

Monitoring

To monitor for these artifacts, take a composite output from your video editing system and send that to a monitor or TV. Because this is a lower quality signal than S-Video/Y-C and component, you don't really need to send it to a good monitor. A consumer TV would work.

Your TV/monitor may have a comb filter setting. On some Sony PVM monitors it is under User config -> "358TRAP FILTER". These settings will make tradeoffs between sharpness and reducing the color artifacts described above. I suggest setting it to whatever gives you the sharpest picture and most color artifacts (which is what you would like to monitor for).

Dealing with these artifacts

Will people see these artifacts? In many case, yes. A lot of people have their TVs hooked up with a composite connection. Even if you are mastering to a digital format like DVD, they may have their DVD player sending a composite video signal to their TV. Keep in mind that these people will always see these artifacts and tend to tune them out (or not notice them) if they aren't obvious. So you only need to go after particularly obvious cases.

To reduce these artifacts, make sure that you don't have extremely high contrast edges in your video and watch out for certain fabrics/textures/patterns. For text, use drop shadows, glows, and anti-aliased edges to reduce contrast on edges. Blur tools can also work.

You can also try building yourself a low pass filter (or search the filters and see if one is named low pass). For Sony Vegas, it is described in my article on Unsharp Mask.

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Also check out my sister site on broadcast monitors.

This site by Glenn Chan. Please email any comments or questions to glennchan /at/ gmail.com