In YUV 4:2:2, the basic unit is composed of two pixels, and occupies four bytes of space. Each pixel has an individual 8 bit Y channel. Then, the first pixel specify an 8 bit U channel, and the second pixel an 8 bit V channel. Both pixels use the same U and V channels.
The sequence of data is the following:
Y1 U1 Y2 V2 Y3 U3 Y4 V4 ....Pixels will be actually reconstructed as follows:
Y1 U1 V2 Y2 U1 V2 Y3 U3 V4 Y4 U3 V4 ...YUV 4:2:2 is commonly used on professional-quality video equipment. The loss of quality due to the reduced U and V information is usually not noticeable, because the human eye is much better at seeing differences in brightness than in color.