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diff --git a/Documentation/userspace-api/media/v4l/pixfmt-nv12mt.rst b/Documentation/userspace-api/media/v4l/pixfmt-nv12mt.rst new file mode 100644 index 000000000000..daac1c16d4f2 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv12mt.rst @@ -0,0 +1,67 @@ +.. Permission is granted to copy, distribute and/or modify this +.. document under the terms of the GNU Free Documentation License, +.. Version 1.1 or any later version published by the Free Software +.. Foundation, with no Invariant Sections, no Front-Cover Texts +.. and no Back-Cover Texts. A copy of the license is included at +.. Documentation/userspace-api/media/fdl-appendix.rst. +.. +.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections + +.. _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. |