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Appendices : Video Formats and Bandwidth Page 235
4.4.4 means that every pixel is sampled for Chroma and Luma value.
The two Chroma values are the result of:
Luma minus Red value
and
Luma minus Blue value
The RGB and 4.4,4 color sampling systems lead to a high bandwidth requirement while preserving color defini-
tion.
They are used by graphics and special effects designers. The maximum Chroma information is required to avoid
artefacts when the picture is processed. There are 3 values per pixel.
Since high bandwidth requirement means expensive equipment, video engineers have developed ingenious
strategies to reduce these requirements in a transparent manner. Fortunately, human vision is less acute for color
than for luminosity. For this reason color sampling can be undertaken at a lower resolution than the luminance
sampling in order to reduce overall bandwidth requirement with no visible impact.
4.2.2
4.2.2 has been widely adopted by the video industry and broadcasters because of its good quality to bandwidth
ratio.
Here, for every four luminance samples, there are two samples of each color difference channel. We have 4 values
for 2 pixels leading to 2 for computation purposes.