Overview: YUV formats

The YUV model defines a color space in terms of one luma and two chrominance components.

There 4 main YUV formats:
- YUV444 : Each point is represented by a (Y,U,V) value. The size of this format is the same with the RGB format size.
- YUV422 : Each block 2x1 is represented by one (U,V) value and two different Y values for each point in that block. The size of this format is smaller than the RGB format size.
- YUV420 : Each block 2x2 is represented by one (U,V) value and four different Y values for each point in that block. The size of this format is smaller than the RGB format and the YUV422 format size.
- YUV411 : Each block 4x1 is represented by one (U,V) value and four different Y values for each point in that block. The size of this format is the same with the YUV420 format size.

We use the YUV formats because the human eye is more sensitive to the luminance than the chrominance. So that we can reduce the chrominance coefficients to reduce the size of the picture or video frame (YUV422, YUV420, YUV411).

Note: in block AxB, A is the horizontal dimension and B is the vertical dimension.

Reference:
- Wikipedia
- http://www.fourcc.org/yuv.php