Chroma Subsampling

This is a method of compressing color info of a signal.  The nomenclature is three digits separeted by two colons.

• 4:4:4 --> No chroma subsampling, each pixel has Y, Cr and Cb values
• 4:2:2 --> Horizontally subsample Cr, Cb signals by a factor of 2
• 4:1:1 --> Horizontally subsampled by a factor of 4
• 4:2:0 --> Subsampled in both the horizontal and vertical dimensions by a factor of 2. Theoretically, the chroma pixel is positioned between the rows and columns as shown in the figure
• 4:1:1 and 4:2:0 are mostly used in JPEG and MPEG