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 2.31. V4L2_PIX_FMT_NV12 4 × 4 pixel image

Byte Order. Each cell is one byte.

start + 0:Y'00Y'01Y'02Y'03
start + 4:Y'10Y'11Y'12Y'13
start + 8:Y'20Y'21Y'22Y'23
start + 12:Y'30Y'31Y'32Y'33
start + 16:Cb00Cr00Cb01Cr01
start + 20:Cb10Cr10Cb11Cr11

Color Sample Location. 

 0 1 2 3
0Y Y Y Y
  C   C 
1Y Y Y Y
2Y Y Y Y
  C   C 
3Y Y Y Y