Dot crawl
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Philips test card with artifacts visible in areas of contact between solid colors (ex: yellow and cyan) and on high horizontal detail ("rainbows" over fine vertical stripes pattern) - click to enlarge Dot crawl (also known as chroma crawl or cross-luma) is a visual defect of color analog video standards when signals are transmitted as composite video, as in terrestrial broadcast television. It consists of moving checkerboard patterns which appear along horizontal color transitions (vertical edges). It results from intermodulation or crosstalk between chrominance and luminance components of the signal, which are imperfectly multiplexed in the frequency domain. The term is more associated with the NTSC analog color TV system, but is also present in PAL (see Chroma dots). Although the interference patterns are slightly different depending on the system used, they have the same cause and the same general principles apply. A related effect, color bleed or rainbow artifacts, is discussed below.
Philips test card with artifacts visible in areas of contact between solid colors (ex: yellow and cyan) and on high horizontal detail ("rainbows" over fine vertical stripes pattern) - click to enlarge]] Dot crawl (also known as chroma crawl or cross-luma) is a visual defect of color analog video standards when signals are transmitted as composite video, as in terrestrial broadcast television. It consists of moving checkerboard patterns which appear along horizontal color transitions (vertical edges). It results from intermodulation or crosstalk between chrominance and luminance components of the signal, which are imperfectly multiplexed in the frequency domain. The term is more associated with the NTSC analog color TV system, but is also present in PAL (see Chroma dots). Although the interference patterns are slightly different depending on the system used, they have the same cause and the same general principles apply. A related effect, color bleed or rainbow artifacts, is discussed below.
References
See also
Composite artifact colors Chroma dots Hanover bars Color framing
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