提交 bd08a0cd 编写于 作者: K Kamil Debski 提交者: Mauro Carvalho Chehab

[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: NKamil Debski <k.debski@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>
上级 91707b8b
...@@ -272,6 +272,7 @@ ...@@ -272,6 +272,7 @@
<!ENTITY sub-grey SYSTEM "v4l/pixfmt-grey.xml"> <!ENTITY sub-grey SYSTEM "v4l/pixfmt-grey.xml">
<!ENTITY sub-nv12 SYSTEM "v4l/pixfmt-nv12.xml"> <!ENTITY sub-nv12 SYSTEM "v4l/pixfmt-nv12.xml">
<!ENTITY sub-nv12m SYSTEM "v4l/pixfmt-nv12m.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-nv16 SYSTEM "v4l/pixfmt-nv16.xml">
<!ENTITY sub-packed-rgb SYSTEM "v4l/pixfmt-packed-rgb.xml"> <!ENTITY sub-packed-rgb SYSTEM "v4l/pixfmt-packed-rgb.xml">
<!ENTITY sub-packed-yuv SYSTEM "v4l/pixfmt-packed-yuv.xml"> <!ENTITY sub-packed-yuv SYSTEM "v4l/pixfmt-packed-yuv.xml">
......
<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:
-->
...@@ -709,6 +709,7 @@ information.</para> ...@@ -709,6 +709,7 @@ information.</para>
&sub-yuv411p; &sub-yuv411p;
&sub-nv12; &sub-nv12;
&sub-nv12m; &sub-nv12m;
&sub-nv12mt;
&sub-nv16; &sub-nv16;
</section> </section>
......
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