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[media] v4l: Documentation for the NV12MT format
Added documentation for V4L2_PIX_FMT_NV12MT format. This is a YUV 4:2:0
format with macro block size of 64x32 and specific order of macro blocks
in the memory.
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
authored by
Kamil Debski
and committed by
Mauro Carvalho Chehab
bd08a0cd
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Documentation/DocBook/media-entities.tmpl
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Documentation/DocBook/media-entities.tmpl
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<!ENTITY sub-grey SYSTEM "v4l/pixfmt-grey.xml">
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<!ENTITY sub-nv12 SYSTEM "v4l/pixfmt-nv12.xml">
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<!ENTITY sub-nv12m SYSTEM "v4l/pixfmt-nv12m.xml">
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<!ENTITY sub-nv12mt SYSTEM "v4l/pixfmt-nv12mt.xml">
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<!ENTITY sub-nv16 SYSTEM "v4l/pixfmt-nv16.xml">
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<!ENTITY sub-packed-rgb SYSTEM "v4l/pixfmt-packed-rgb.xml">
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<!ENTITY sub-packed-yuv SYSTEM "v4l/pixfmt-packed-yuv.xml">
Documentation/DocBook/v4l/nv12mt.gif
Documentation/DocBook/v4l/nv12mt.gif
This is a binary file and will not be displayed.
Documentation/DocBook/v4l/nv12mt_example.gif
Documentation/DocBook/v4l/nv12mt_example.gif
This is a binary file and will not be displayed.
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Documentation/DocBook/v4l/pixfmt-nv12mt.xml
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Documentation/DocBook/v4l/pixfmt-nv12mt.xml
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<refentry>
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<refmeta>
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<refentrytitle>V4L2_PIX_FMT_NV12MT ('TM12')</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname id="V4L2-PIX-FMT-NV12MT"><constant>V4L2_PIX_FMT_NV12MT
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</constant></refname>
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<refpurpose>Formats with ½ horizontal and vertical
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chroma resolution. This format has two planes - one for luminance and one for
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chrominance. Chroma samples are interleaved. The difference to
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<constant>V4L2_PIX_FMT_NV12</constant> is the memory layout. Pixels are
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grouped in macroblocks of 64x32 size. The order of macroblocks in memory is
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also not standard.
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</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<para>This is the two-plane versions of the YUV 4:2:0 format where data
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is grouped into 64x32 macroblocks. The three components are separated into two
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sub-images or planes. The Y plane has one byte per pixel and pixels are grouped
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into 64x32 macroblocks. The CbCr plane has the same width, in bytes, as the Y
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plane (and the image), but is half as tall in pixels. The chroma plane is also
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grouped into 64x32 macroblocks.</para>
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<para>Width of the buffer has to be aligned to the multiple of 128, and
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height alignment is 32. Every four adjactent buffers - two horizontally and two
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vertically are grouped together and are located in memory in Z or flipped Z
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order. </para>
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<para>Layout of macroblocks in memory is presented in the following
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figure.</para>
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<para><figure id="nv12mt">
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<title><constant>V4L2_PIX_FMT_NV12MT</constant> macroblock Z shape
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memory layout</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="nv12mt.gif" format="GIF" />
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</imageobject>
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</mediaobject>
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</figure>
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The requirement that width is multiple of 128 is implemented because,
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the Z shape cannot be cut in half horizontally. In case the vertical resolution
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of macroblocks is odd then the last row of macroblocks is arranged in a linear
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order. </para>
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<para>In case of chroma the layout is identical. Cb and Cr samples are
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interleaved. Height of the buffer is aligned to 32.
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</para>
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<example>
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<title>Memory layout of macroblocks in <constant>V4L2_PIX_FMT_NV12
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</constant> format pixel image - extreme case</title>
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<para>
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<figure id="nv12mt">
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<title>Example <constant>V4L2_PIX_FMT_NV12MT</constant> memory
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layout of macroblocks</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="nv12mt_example.gif" format="GIF" />
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</imageobject>
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</mediaobject>
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</figure>
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Memory layout of macroblocks of <constant>V4L2_PIX_FMT_NV12MT
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</constant> format in most extreme case.
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</para>
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</example>
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</refsect1>
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</refentry>
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<!--
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Local Variables:
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mode: sgml
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sgml-parent-document: "pixfmt.sgml"
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indent-tabs-mode: nil
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End:
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-->