2.6.23. 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 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