V4L2_PIX_FMT_YUV420M, V4L2_PIX_FMT_YVU420M — Variation of V4L2_PIX_FMT_YUV420 and
V4L2_PIX_FMT_YVU420 with planes non contiguous
in memory.
This is a multi-planar format, 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_YUV420M the Cb data
constitutes the second plane which is half the width and half
the height of the Y plane (and of the image). Each Cb belongs to four
pixels, a two-by-two square of the image. For example,
Cb0 belongs to Y'00,
Y'01, Y'10, and
Y'11. The Cr data, just like the Cb plane, is
in the third plane.
V4L2_PIX_FMT_YVU420M is the same except
the Cr data is stored in the second plane and the Cb data in the third plane.
If the Y plane has pad bytes after each row, then the Cb and Cr 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_YUV420M and
V4L2_PIX_FMT_YVU420M are intended to be
used only in drivers and applications that support the multi-planar API,
described in the section called “Single- and multi-planar APIs”.
Example 2.25. V4L2_PIX_FMT_YUV420M 4 × 4
pixel image
Byte Order. Each cell is one byte.
| start0 + 0: | Y'00 | Y'01 | Y'02 | Y'03 |
| start0 + 4: | Y'10 | Y'11 | Y'12 | Y'13 |
| start0 + 8: | Y'20 | Y'21 | Y'22 | Y'23 |
| start0 + 12: | Y'30 | Y'31 | Y'32 | Y'33 |
| start1 + 0: | Cb00 | Cb01 | ||
| start1 + 2: | Cb10 | Cb11 | ||
| start2 + 0: | Cr00 | Cr01 | ||
| start2 + 2: | Cr10 | Cr11 |
Color Sample Location.
| 0 | 1 | 2 | 3 | ||||
| 0 | Y | Y | Y | Y | |||
| C | C | ||||||
| 1 | Y | Y | Y | Y | |||
| 2 | Y | Y | Y | Y | |||
| C | C | ||||||
| 3 | Y | Y | Y | Y |