| .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
| |
| .. _V4L2-PIX-FMT-NV12MT: |
| |
| **************************** |
| V4L2_PIX_FMT_NV12MT ('TM12') |
| **************************** |
| |
| Formats with ½ horizontal and vertical chroma resolution. This format |
| has two planes - one for luminance and one for chrominance. Chroma |
| samples are interleaved. The difference to ``V4L2_PIX_FMT_NV12`` is the |
| memory layout. Pixels are grouped in macroblocks of 64x32 size. The |
| order of macroblocks in memory is also not standard. |
| |
| |
| Description |
| =========== |
| |
| This is the two-plane versions of the YUV 4:2:0 format where data is |
| grouped into 64x32 macroblocks. The three components are separated into |
| two sub-images or planes. The Y plane has one byte per pixel and pixels |
| are grouped into 64x32 macroblocks. The CbCr plane has the same width, |
| in bytes, as the Y plane (and the image), but is half as tall in pixels. |
| The chroma plane is also grouped into 64x32 macroblocks. |
| |
| Width of the buffer has to be aligned to the multiple of 128, and height |
| alignment is 32. Every four adjacent buffers - two horizontally and two |
| vertically are grouped together and are located in memory in Z or |
| flipped Z order. |
| |
| Layout of macroblocks in memory is presented in the following figure. |
| |
| |
| .. _nv12mt: |
| |
| .. kernel-figure:: nv12mt.svg |
| :alt: nv12mt.svg |
| :align: center |
| |
| V4L2_PIX_FMT_NV12MT macroblock Z shape memory layout |
| |
| The requirement that width is multiple of 128 is implemented because, |
| the Z shape cannot be cut in half horizontally. In case the vertical |
| resolution of macroblocks is odd then the last row of macroblocks is |
| arranged in a linear order. |
| |
| In case of chroma the layout is identical. Cb and Cr samples are |
| interleaved. Height of the buffer is aligned to 32. |
| |
| |
| .. _nv12mt_ex: |
| |
| .. kernel-figure:: nv12mt_example.svg |
| :alt: nv12mt_example.svg |
| :align: center |
| |
| Example V4L2_PIX_FMT_NV12MT memory layout of macroblocks |
| |
| Memory layout of macroblocks of ``V4L2_PIX_FMT_NV12MT`` format in most |
| extreme case. |
