Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and digital video data, and is often one of the last stages of audio production to compact disc.
Hepatic porphyria. Hepatic porphyrias is a form of porphyria in which the enzyme deficiency occurs in the liver. Examples include (in order of synthesis pathway): Acute intermittent porphyria. Porphyria cutanea tarda and Hepatoerythropoietic porphyria.
It is a component of hemoglobin, the molecule that carries oxygen in the blood. Hepatoerythropoietic porphyria has been described as a homozygous form of porphyria cutanea tarda, although it can also be caused if two different mutations occur at the same locus.