• Chroma Subsampling is the process whereby the color information in the image is sampled at a lower resolution than the original.

• It is the process of reduction of color resolution in digital component video signals in order to save storage and bandwidth.

• The color components are compressed by sampling them at a lower rate than the brightness (luma).

• A reduced color resolution in digital component video signals. To accommodate storage and bandwidth limitations, the two color components (Cb. Cr) in digital video signals are compressed by sampling them at a lower rate than the brightness (Y). Color information is actually discarded. Y is brightness (luma), and Cb and Cr are the U and V color difference signals.

• In chroma Subsampling, only the colors are compressed not the luma because the eye is more sensitive to brightness than to the color components.

• Numbers are given stating how many pixel values, per four original pixels, are actually transmitted.

4:4:4 (Cb/Cr Same as Luma)

• The chroma Subsampling scheme “4:4:4” indicates that no chroma Subsampling is used: each pixel's Y, Cb and Cr values are transmitted, 4 for each of Y, Cb, Cr.

4:2:2 (1/2 the Luma Samples)

• Cb and Cr are sampled at half the horizontal resolution of the luma (Y). Co-sited means that Cb/Cr samples are taken at the same time as Y. Considered high quality, 4:2:2 is used in professional recording like Digital Cameras.

4:1:1 (1/4 the Luma Samples)

• Cb and Cr are sampled at one quarter the horizontal resolution. Co-sited means that Cb/Cr samples are taken at the same time as the Y, and co-sited 4:1:1 is used in DV, DVCAM and DVCPRO formats.

4:2:0 (1/4 the Luma Samples)

• The scheme “4:2:0” subsamples in both the horizontal and vertical dimensions by a factor of 2. Theoretically, an average chroma pixel is positioned between the rows and columns.