V4L2_PIX_FMT_NV12, V4L2_PIX_FMT_NV21 — Formats with ½ horizontal and vertical
chroma resolution, also known as YUV 4:2:0. One luminance and one
chrominance plane with alternating chroma samples as opposed to
V4L2_PIX_FMT_YVU420
These are two-plane versions of the YUV 4:2:0 format.
The three components are separated into two sub-images or planes. The
Y plane is first. The Y plane has one byte per pixel. For
V4L2_PIX_FMT_NV12, a combined CbCr plane
immediately follows the Y plane in memory. The CbCr plane is the same
width, in bytes, as the Y plane (and of the image), but is half as
tall in pixels. Each CbCr pair belongs to four pixels. For example,
Cb0/Cr0 belongs to
Y'00, Y'01,
Y'10, Y'11.
V4L2_PIX_FMT_NV21 is the same except the Cb and
Cr bytes are swapped, the CrCb plane starts with a Cr byte.
If the Y plane has pad bytes after each row, then the CbCr plane has as many pad bytes after its rows.
Example 2.25. V4L2_PIX_FMT_NV12 4 × 4
pixel image
Byte Order. Each cell is one byte.
| start + 0: | Y'00 | Y'01 | Y'02 | Y'03 |
| start + 4: | Y'10 | Y'11 | Y'12 | Y'13 |
| start + 8: | Y'20 | Y'21 | Y'22 | Y'23 |
| start + 12: | Y'30 | Y'31 | Y'32 | Y'33 |
| start + 16: | Cb00 | Cr00 | Cb01 | Cr01 |
| start + 20: | Cb10 | Cr10 | Cb11 | 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 |