V4L2_PIX_FMT_YUV420-- Planar formats with ½ horizontal and vertical chroma resolution, also known as YUV 4:2:0
These are planar formats, as opposed to a packed format.
The three components are separated into three sub- images or planes.
The Y plane is first. The Y plane has one byte per pixel. For
V4L2_PIX_FMT_YVU420, the Cr plane immediately
follows the Y plane in memory. The Cr plane is half the width and half
the height of the Y plane (and of the image). Each Cr belongs to four
pixels, a two-by-two square of the image. For example,
Cr0 belongs to Y'00,
Y'01, Y'10, and
Y'11. Following the Cr plane is the Cb plane,
just like the Cr plane.
the same except the Cb plane comes first, then the Cr plane.
If the Y plane has pad bytes after each row, then the Cr and Cb planes have half as many pad bytes after their rows. In other words, two Cx rows (including padding) is exactly as long as one Y row (including padding).
V4L2_PIX_FMT_YVU420 4 × 4
Byte Order. Each cell is one byte.