2.7.25. V4L2_PIX_FMT_NV12 (‘NV12’), V4L2_PIX_FMT_NV21 (‘NV21’)

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

2.7.25.1. Description

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.

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