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Cross luminance artefact
From Encyclopedia PRO
An artefact of encoded video, also known as dot crawl or cross-luminance. It occurs in the video picture around the edges of highly saturated colours as a continuous series of crawling dots and is a result of colour information being confused as luminance information by the decoder circuits.
Cross Luminance Artefact occurs when the video decoder incorrectly interprets chroma information (color) to be high-frequency luma information (brightness).