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Commit bd08a0cd authored by Kamil Debski's avatar Kamil Debski Committed by Mauro Carvalho Chehab
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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: default avatarKamil Debski <k.debski@samsung.com>
Signed-off-by: default avatarKyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 91707b8b

Documentation/DocBook/media-entities.tmpl

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@@ -272,6 +272,7 @@ 
<!ENTITY sub-grey SYSTEM "v4l/pixfmt-grey.xml">

<!ENTITY sub-nv12 SYSTEM "v4l/pixfmt-nv12.xml">

<!ENTITY sub-nv12m SYSTEM "v4l/pixfmt-nv12m.xml">

<!ENTITY sub-nv12mt SYSTEM "v4l/pixfmt-nv12mt.xml">

<!ENTITY sub-nv16 SYSTEM "v4l/pixfmt-nv16.xml">

<!ENTITY sub-packed-rgb SYSTEM "v4l/pixfmt-packed-rgb.xml">

<!ENTITY sub-packed-yuv SYSTEM "v4l/pixfmt-packed-yuv.xml">

Documentation/DocBook/v4l/nv12mt.gif

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Documentation/DocBook/v4l/nv12mt_example.gif

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Documentation/DocBook/v4l/pixfmt-nv12mt.xml

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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">

	    <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>



  <!--

Local Variables:

mode: sgml

sgml-parent-document: "pixfmt.sgml"

indent-tabs-mode: nil

End:

  -->

Documentation/DocBook/v4l/pixfmt.xml

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@@ -709,6 +709,7 @@ information.</para> 
    &sub-yuv411p;

    &sub-nv12;

    &sub-nv12m;

    &sub-nv12mt;

    &sub-nv16;

  </section>