http://de.wikipedia.org/wiki/Farbs%C3%A4ttigung


http://en.wikipedia.org/wiki/Chroma_subsampling
video: 
The signal is divided into a luma (Y') component and two color difference components (chroma).
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In human vision there are two chromatic channels as well as a luminance channel, and in color science 
there are two chromatic dimensions as well as a luminance dimension. In neither the vision nor the 
science is there complete independence of the chromatic and the luminance.
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The subsampling scheme is commonly expressed as a three part ratio J:a:b (e.g. 4:2:2)
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expressions like "4:2:2 YUV" always refer to 4:2:2 Y'CbCr
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