2.6.25. V4L2_PIX_FMT_NV12M (‘NM12’), V4L2_PIX_FMT_NV21M (‘NM21’), V4L2_PIX_FMT_NV12MT_16X16¶
V4L2_PIX_FMT_NV21M
V4L2_PIX_FMT_NV12MT_16X16
Variation of V4L2_PIX_FMT_NV12 and V4L2_PIX_FMT_NV21 with planes
non contiguous in memory.
2.6.25.1. Description¶
This is a multi-planar, two-plane version of the YUV 4:2:0 format. The
three components are separated into two sub-images or planes.
V4L2_PIX_FMT_NV12M differs from V4L2_PIX_FMT_NV12 in that the
two planes are non-contiguous in memory, i.e. the chroma plane do not
necessarily immediately follows the luma plane. The luminance data
occupies the first plane. The Y plane has one byte per pixel. In the
second plane there is a chrominance data with alternating chroma
samples. 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_NV12MT_16X16 is the tiled version of
V4L2_PIX_FMT_NV12M with 16x16 macroblock tiles. Here pixels are
arranged in 16x16 2D tiles and tiles are arranged in linear order in
memory. V4L2_PIX_FMT_NV21M is the same as V4L2_PIX_FMT_NV12M
except the Cb and Cr bytes are swapped, the CrCb plane starts with a Cr
byte.
V4L2_PIX_FMT_NV12M is intended to be used only in drivers and
applications that support the multi-planar API, described in
Single- and multi-planar APIs.
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.
| 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 | Cr00 | Cb01 | Cr01 |
| start1 + 4: | 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 | |||