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- <refentry>
- <refmeta>
- <refentrytitle>V4L2_PIX_FMT_NV12MT ('TM12')</refentrytitle>
- &manvol;
- </refmeta>
- <refnamediv>
- <refname id="V4L2-PIX-FMT-NV12MT"><constant>V4L2_PIX_FMT_NV12MT
-</constant></refname>
- <refpurpose>Formats with &frac12; horizontal and vertical
-chroma resolution. This format has two planes - one for luminance and one for
-chrominance. Chroma samples are interleaved. The difference to
-<constant>V4L2_PIX_FMT_NV12</constant> is the memory layout. Pixels are
-grouped in macroblocks of 64x32 size. The order of macroblocks in memory is
-also not standard.
- </refpurpose>
- </refnamediv>
- <refsect1>
- <title>Description</title>
-
- <para>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.</para>
- <para>Width of the buffer has to be aligned to the multiple of 128, and
-height alignment is 32. Every four adjactent buffers - two horizontally and two
-vertically are grouped together and are located in memory in Z or flipped Z
-order. </para>
- <para>Layout of macroblocks in memory is presented in the following
-figure.</para>
- <para><figure id="nv12mt">
- <title><constant>V4L2_PIX_FMT_NV12MT</constant> macroblock Z shape
-memory layout</title>
- <mediaobject>
- <imageobject>
- <imagedata fileref="nv12mt.gif" format="GIF" />
- </imageobject>
- </mediaobject>
- </figure>
- 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. </para>
- <para>In case of chroma the layout is identical. Cb and Cr samples are
-interleaved. Height of the buffer is aligned to 32.
- </para>
- <example>
- <title>Memory layout of macroblocks in <constant>V4L2_PIX_FMT_NV12
-</constant> format pixel image - extreme case</title>
- <para>
- <figure id="nv12mt_ex">
- <title>Example <constant>V4L2_PIX_FMT_NV12MT</constant> memory
-layout of macroblocks</title>
- <mediaobject>
- <imageobject>
- <imagedata fileref="nv12mt_example.gif" format="GIF" />
- </imageobject>
- </mediaobject>
- </figure>
- Memory layout of macroblocks of <constant>V4L2_PIX_FMT_NV12MT
-</constant> format in most extreme case.
- </para>
- </example>
- </refsect1>
- </refentry>