  <title>Image Formats</title>

  <para>The V4L2 API was primarily designed for devices exchanging
image data with applications. The
<structname>v4l2_pix_format</structname> and <structname>v4l2_pix_format_mplane
</structname> structures define the format and layout of an image in memory.
The former is used with the single-planar API, while the latter is used with the
multi-planar version (see <xref linkend="planar-apis"/>). Image formats are
negotiated with the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video
capturing and output, for overlay frame buffer formats see also
&VIDIOC-G-FBUF;.)</para>

<section>
  <title>Single-planar format structure</title>
  <table pgwide="1" frame="none" id="v4l2-pix-format">
    <title>struct <structname>v4l2_pix_format</structname></title>
    <tgroup cols="3">
      &cs-str;
      <tbody valign="top">
	<row>
	  <entry>__u32</entry>
	  <entry><structfield>width</structfield></entry>
	  <entry>Image width in pixels.</entry>
	</row>
	<row>
	  <entry>__u32</entry>
	  <entry><structfield>height</structfield></entry>
	  <entry>Image height in pixels.</entry>
	</row>
	<row>
	  <entry spanname="hspan">Applications set these fields to
request an image size, drivers return the closest possible values. In
case of planar formats the <structfield>width</structfield> and
<structfield>height</structfield> applies to the largest plane. To
avoid ambiguities drivers must return values rounded up to a multiple
of the scale factor of any smaller planes. For example when the image
format is YUV 4:2:0, <structfield>width</structfield> and
<structfield>height</structfield> must be multiples of two.</entry>
	</row>
	<row>
	  <entry>__u32</entry>
	  <entry><structfield>pixelformat</structfield></entry>
	  <entry>The pixel format or type of compression, set by the
application. This is a little endian <link
linkend="v4l2-fourcc">four character code</link>. V4L2 defines
standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref
linkend="yuv-formats" />, and reserved codes in <xref
linkend="reserved-formats" /></entry>
	</row>
	<row>
	  <entry>&v4l2-field;</entry>
	  <entry><structfield>field</structfield></entry>
	  <entry>Video images are typically interlaced. Applications
can request to capture or output only the top or bottom field, or both
fields interlaced or sequentially stored in one buffer or alternating
in separate buffers. Drivers return the actual field order selected.
For details see <xref linkend="field-order" />.</entry>
	</row>
	<row>
	  <entry>__u32</entry>
	  <entry><structfield>bytesperline</structfield></entry>
	  <entry>Distance in bytes between the leftmost pixels in two
adjacent lines.</entry>
	</row>
	<row>
	  <entry spanname="hspan"><para>Both applications and drivers
can set this field to request padding bytes at the end of each line.
Drivers however may ignore the value requested by the application,
returning <structfield>width</structfield> times bytes per pixel or a
larger value required by the hardware. That implies applications can
just set this field to zero to get a reasonable
default.</para><para>Video hardware may access padding bytes,
therefore they must reside in accessible memory. Consider cases where
padding bytes after the last line of an image cross a system page
boundary. Input devices may write padding bytes, the value is
undefined. Output devices ignore the contents of padding
bytes.</para><para>When the image format is planar the
<structfield>bytesperline</structfield> value applies to the largest
plane and is divided by the same factor as the
<structfield>width</structfield> field for any smaller planes. For
example the Cb and Cr planes of a YUV 4:2:0 image have half as many
padding bytes following each line as the Y plane. To avoid ambiguities
drivers must return a <structfield>bytesperline</structfield> value
rounded up to a multiple of the scale factor.</para></entry>
	</row>
	<row>
	  <entry>__u32</entry>
	  <entry><structfield>sizeimage</structfield></entry>
	  <entry>Size in bytes of the buffer to hold a complete image,
set by the driver. Usually this is
<structfield>bytesperline</structfield> times
<structfield>height</structfield>. When the image consists of variable
length compressed data this is the maximum number of bytes required to
hold an image.</entry>
	</row>
	<row>
	  <entry>&v4l2-colorspace;</entry>
	  <entry><structfield>colorspace</structfield></entry>
	  <entry>This information supplements the
<structfield>pixelformat</structfield> and must be set by the driver,
see <xref linkend="colorspaces" />.</entry>
	</row>
	<row>
	  <entry>__u32</entry>
	  <entry><structfield>priv</structfield></entry>
	  <entry>Reserved for custom (driver defined) additional
information about formats. When not used drivers and applications must
set this field to zero.</entry>
	</row>
      </tbody>
    </tgroup>
  </table>
</section>

<section>
  <title>Multi-planar format structures</title>
  <para>The <structname>v4l2_plane_pix_format</structname> structures define
    size and layout for each of the planes in a multi-planar format.
    The <structname>v4l2_pix_format_mplane</structname> structure contains
    information common to all planes (such as image width and height) and
    an array of <structname>v4l2_plane_pix_format</structname> structures,
    describing all planes of that format.</para>
  <table pgwide="1" frame="none" id="v4l2-plane-pix-format">
    <title>struct <structname>vl42_plane_pix_format</structname></title>
    <tgroup cols="3">
      &cs-str;
      <tbody valign="top">
        <row>
          <entry>__u32</entry>
          <entry><structfield>sizeimage</structfield></entry>
          <entry>Maximum size in bytes required for image data in this plane.
          </entry>
        </row>
        <row>
          <entry>__u16</entry>
          <entry><structfield>bytesperline</structfield></entry>
          <entry>Distance in bytes between the leftmost pixels in two adjacent
            lines.</entry>
        </row>
        <row>
          <entry>__u16</entry>
          <entry><structfield>reserved[7]</structfield></entry>
          <entry>Reserved for future extensions. Should be zeroed by the
           application.</entry>
        </row>
      </tbody>
    </tgroup>
  </table>
  <table pgwide="1" frame="none" id="v4l2-pix-format-mplane">
    <title>struct <structname>v4l2_pix_format_mplane</structname></title>
    <tgroup cols="3">
      &cs-str;
      <tbody valign="top">
        <row>
          <entry>__u32</entry>
          <entry><structfield>width</structfield></entry>
          <entry>Image width in pixels.</entry>
        </row>
        <row>
          <entry>__u32</entry>
          <entry><structfield>height</structfield></entry>
          <entry>Image height in pixels.</entry>
        </row>
        <row>
          <entry>__u32</entry>
          <entry><structfield>pixelformat</structfield></entry>
          <entry>The pixel format. Both single- and multi-planar four character
codes can be used.</entry>
        </row>
        <row>
          <entry>&v4l2-field;</entry>
          <entry><structfield>field</structfield></entry>
          <entry>See &v4l2-pix-format;.</entry>
        </row>
        <row>
          <entry>&v4l2-colorspace;</entry>
          <entry><structfield>colorspace</structfield></entry>
          <entry>See &v4l2-pix-format;.</entry>
        </row>
        <row>
          <entry>&v4l2-plane-pix-format;</entry>
          <entry><structfield>plane_fmt[VIDEO_MAX_PLANES]</structfield></entry>
          <entry>An array of structures describing format of each plane this
          pixel format consists of. The number of valid entries in this array
          has to be put in the <structfield>num_planes</structfield>
          field.</entry>
        </row>
        <row>
          <entry>__u8</entry>
          <entry><structfield>num_planes</structfield></entry>
          <entry>Number of planes (i.e. separate memory buffers) for this format
          and the number of valid entries in the
          <structfield>plane_fmt</structfield> array.</entry>
        </row>
        <row>
          <entry>__u8</entry>
          <entry><structfield>reserved[11]</structfield></entry>
          <entry>Reserved for future extensions. Should be zeroed by the
           application.</entry>
        </row>
      </tbody>
    </tgroup>
  </table>
</section>

  <section>
    <title>Standard Image Formats</title>

    <para>In order to exchange images between drivers and
applications, it is necessary to have standard image data formats
which both sides will interpret the same way. V4L2 includes several
such formats, and this section is intended to be an unambiguous
specification of the standard image data formats in V4L2.</para>

    <para>V4L2 drivers are not limited to these formats, however.
Driver-specific formats are possible. In that case the application may
depend on a codec to convert images to one of the standard formats
when needed. But the data can still be stored and retrieved in the
proprietary format. For example, a device may support a proprietary
compressed format. Applications can still capture and save the data in
the compressed format, saving much disk space, and later use a codec
to convert the images to the X Windows screen format when the video is
to be displayed.</para>

    <para>Even so, ultimately, some standard formats are needed, so
the V4L2 specification would not be complete without well-defined
standard formats.</para>

    <para>The V4L2 standard formats are mainly uncompressed formats. The
pixels are always arranged in memory from left to right, and from top
to bottom. The first byte of data in the image buffer is always for
the leftmost pixel of the topmost row. Following that is the pixel
immediately to its right, and so on until the end of the top row of
pixels. Following the rightmost pixel of the row there may be zero or
more bytes of padding to guarantee that each row of pixel data has a
certain alignment. Following the pad bytes, if any, is data for the
leftmost pixel of the second row from the top, and so on. The last row
has just as many pad bytes after it as the other rows.</para>

    <para>In V4L2 each format has an identifier which looks like
<constant>PIX_FMT_XXX</constant>, defined in the <link
linkend="videodev">videodev.h</link> header file. These identifiers
represent <link linkend="v4l2-fourcc">four character (FourCC) codes</link>
which are also listed below, however they are not the same as those
used in the Windows world.</para>

    <para>For some formats, data is stored in separate, discontiguous
memory buffers. Those formats are identified by a separate set of FourCC codes
and are referred to as "multi-planar formats". For example, a YUV422 frame is
normally stored in one memory buffer, but it can also be placed in two or three
separate buffers, with Y component in one buffer and CbCr components in another
in the 2-planar version or with each component in its own buffer in the
3-planar case. Those sub-buffers are referred to as "planes".</para>
  </section>

  <section id="colorspaces">
    <title>Colorspaces</title>

    <para>[intro]</para>

    <!-- See proposal by Billy Biggs, video4linux-list@redhat.com
on 11 Oct 2002, subject: "Re: [V4L] Re: v4l2 api", and
http://vektor.theorem.ca/graphics/ycbcr/ and
http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html -->

    <para>
      <variablelist>
	<varlistentry>
	  <term>Gamma Correction</term>
	  <listitem>
	    <para>[to do]</para>
	    <para>E'<subscript>R</subscript> = f(R)</para>
	    <para>E'<subscript>G</subscript> = f(G)</para>
	    <para>E'<subscript>B</subscript> = f(B)</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>Construction of luminance and color-difference
signals</term>
	  <listitem>
	    <para>[to do]</para>
	    <para>E'<subscript>Y</subscript> =
Coeff<subscript>R</subscript> E'<subscript>R</subscript>
+ Coeff<subscript>G</subscript> E'<subscript>G</subscript>
+ Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
	    <para>(E'<subscript>R</subscript> - E'<subscript>Y</subscript>) = E'<subscript>R</subscript>
- Coeff<subscript>R</subscript> E'<subscript>R</subscript>
- Coeff<subscript>G</subscript> E'<subscript>G</subscript>
- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
	    <para>(E'<subscript>B</subscript> - E'<subscript>Y</subscript>) = E'<subscript>B</subscript>
- Coeff<subscript>R</subscript> E'<subscript>R</subscript>
- Coeff<subscript>G</subscript> E'<subscript>G</subscript>
- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>Re-normalized color-difference signals</term>
	  <listitem>
	    <para>The color-difference signals are scaled back to unity
range [-0.5;+0.5]:</para>
	    <para>K<subscript>B</subscript> = 0.5 / (1 - Coeff<subscript>B</subscript>)</para>
	    <para>K<subscript>R</subscript> = 0.5 / (1 - Coeff<subscript>R</subscript>)</para>
	    <para>P<subscript>B</subscript> =
K<subscript>B</subscript> (E'<subscript>B</subscript> - E'<subscript>Y</subscript>) =
  0.5 (Coeff<subscript>R</subscript> / Coeff<subscript>B</subscript>) E'<subscript>R</subscript>
+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>B</subscript>) E'<subscript>G</subscript>
+ 0.5 E'<subscript>B</subscript></para>
	    <para>P<subscript>R</subscript> =
K<subscript>R</subscript> (E'<subscript>R</subscript> - E'<subscript>Y</subscript>) =
  0.5 E'<subscript>R</subscript>
+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>R</subscript>) E'<subscript>G</subscript>
+ 0.5 (Coeff<subscript>B</subscript> / Coeff<subscript>R</subscript>) E'<subscript>B</subscript></para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>Quantization</term>
	  <listitem>
	    <para>[to do]</para>
	    <para>Y' = (Lum. Levels - 1) &middot; E'<subscript>Y</subscript> + Lum. Offset</para>
	    <para>C<subscript>B</subscript> = (Chrom. Levels - 1)
&middot; P<subscript>B</subscript> + Chrom. Offset</para>
	    <para>C<subscript>R</subscript> = (Chrom. Levels - 1)
&middot; P<subscript>R</subscript> + Chrom. Offset</para>
	    <para>Rounding to the nearest integer and clamping to the range
[0;255] finally yields the digital color components Y'CbCr
stored in YUV images.</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </para>

    <example>
      <title>ITU-R Rec. BT.601 color conversion</title>

      <para>Forward Transformation</para>

      <programlisting>
int ER, EG, EB;         /* gamma corrected RGB input [0;255] */
int Y1, Cb, Cr;         /* output [0;255] */

double r, g, b;         /* temporaries */
double y1, pb, pr;

int
clamp (double x)
{
	int r = x;      /* round to nearest */

	if (r &lt; 0)         return 0;
	else if (r &gt; 255)  return 255;
	else               return r;
}

r = ER / 255.0;
g = EG / 255.0;
b = EB / 255.0;

y1  =  0.299  * r + 0.587 * g + 0.114  * b;
pb  = -0.169  * r - 0.331 * g + 0.5    * b;
pr  =  0.5    * r - 0.419 * g - 0.081  * b;

Y1 = clamp (219 * y1 + 16);
Cb = clamp (224 * pb + 128);
Cr = clamp (224 * pr + 128);

/* or shorter */

y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB;

Y1 = clamp ( (219 / 255.0)                    *       y1  + 16);
Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128);
Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128);
      </programlisting>

      <para>Inverse Transformation</para>

      <programlisting>
int Y1, Cb, Cr;         /* gamma pre-corrected input [0;255] */
int ER, EG, EB;         /* output [0;255] */

double r, g, b;         /* temporaries */
double y1, pb, pr;

int
clamp (double x)
{
	int r = x;      /* round to nearest */

	if (r &lt; 0)         return 0;
	else if (r &gt; 255)  return 255;
	else               return r;
}

y1 = (255 / 219.0) * (Y1 - 16);
pb = (255 / 224.0) * (Cb - 128);
pr = (255 / 224.0) * (Cr - 128);

r = 1.0 * y1 + 0     * pb + 1.402 * pr;
g = 1.0 * y1 - 0.344 * pb - 0.714 * pr;
b = 1.0 * y1 + 1.772 * pb + 0     * pr;

ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */
EG = clamp (g * 255);
EB = clamp (b * 255);
      </programlisting>
    </example>

    <table pgwide="1" id="v4l2-colorspace" orient="land">
      <title>enum v4l2_colorspace</title>
      <tgroup cols="11" align="center">
	<colspec align="left" />
	<colspec align="center" />
	<colspec align="left" />
	<colspec colname="cr" />
	<colspec colname="cg" />
	<colspec colname="cb" />
	<colspec colname="wp" />
	<colspec colname="gc" />
	<colspec colname="lum" />
	<colspec colname="qy" />
	<colspec colname="qc" />
	<spanspec namest="cr" nameend="cb" spanname="chrom" />
	<spanspec namest="qy" nameend="qc" spanname="quant" />
	<spanspec namest="lum" nameend="qc" spanname="spam" />
	<thead>
	  <row>
	    <entry morerows="1">Identifier</entry>
	    <entry morerows="1">Value</entry>
	    <entry morerows="1">Description</entry>
	    <entry spanname="chrom">Chromaticities<footnote>
		<para>The coordinates of the color primaries are
given in the CIE system (1931)</para>
	      </footnote></entry>
	    <entry morerows="1">White Point</entry>
	    <entry morerows="1">Gamma Correction</entry>
	    <entry morerows="1">Luminance E'<subscript>Y</subscript></entry>
	    <entry spanname="quant">Quantization</entry>
	  </row>
	  <row>
	    <entry>Red</entry>
	    <entry>Green</entry>
	    <entry>Blue</entry>
	    <entry>Y'</entry>
	    <entry>Cb, Cr</entry>
	  </row>
	</thead>
	<tbody valign="top">
	  <row>
	    <entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry>
	    <entry>1</entry>
	    <entry>NTSC/PAL according to <xref linkend="smpte170m" />,
<xref linkend="itu601" /></entry>
	    <entry>x&nbsp;=&nbsp;0.630, y&nbsp;=&nbsp;0.340</entry>
	    <entry>x&nbsp;=&nbsp;0.310, y&nbsp;=&nbsp;0.595</entry>
	    <entry>x&nbsp;=&nbsp;0.155, y&nbsp;=&nbsp;0.070</entry>
	    <entry>x&nbsp;=&nbsp;0.3127, y&nbsp;=&nbsp;0.3290,
	    Illuminant D<subscript>65</subscript></entry>
	    <entry>E' = 4.5&nbsp;I&nbsp;for&nbsp;I&nbsp;&le;0.018,
1.099&nbsp;I<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&lt;&nbsp;I</entry>
	    <entry>0.299&nbsp;E'<subscript>R</subscript>
+&nbsp;0.587&nbsp;E'<subscript>G</subscript>
+&nbsp;0.114&nbsp;E'<subscript>B</subscript></entry>
	    <entry>219&nbsp;E'<subscript>Y</subscript>&nbsp;+&nbsp;16</entry>
	    <entry>224&nbsp;P<subscript>B,R</subscript>&nbsp;+&nbsp;128</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry>
	    <entry>2</entry>
	    <entry>1125-Line (US) HDTV, see <xref
linkend="smpte240m" /></entry>
	    <entry>x&nbsp;=&nbsp;0.630, y&nbsp;=&nbsp;0.340</entry>
	    <entry>x&nbsp;=&nbsp;0.310, y&nbsp;=&nbsp;0.595</entry>
	    <entry>x&nbsp;=&nbsp;0.155, y&nbsp;=&nbsp;0.070</entry>
	    <entry>x&nbsp;=&nbsp;0.3127, y&nbsp;=&nbsp;0.3290,
	    Illuminant D<subscript>65</subscript></entry>
	    <entry>E' = 4&nbsp;I&nbsp;for&nbsp;I&nbsp;&le;0.0228,
1.1115&nbsp;I<superscript>0.45</superscript>&nbsp;-&nbsp;0.1115&nbsp;for&nbsp;0.0228&nbsp;&lt;&nbsp;I</entry>
	    <entry>0.212&nbsp;E'<subscript>R</subscript>
+&nbsp;0.701&nbsp;E'<subscript>G</subscript>
+&nbsp;0.087&nbsp;E'<subscript>B</subscript></entry>
	    <entry>219&nbsp;E'<subscript>Y</subscript>&nbsp;+&nbsp;16</entry>
	    <entry>224&nbsp;P<subscript>B,R</subscript>&nbsp;+&nbsp;128</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_COLORSPACE_REC709</constant></entry>
	    <entry>3</entry>
	    <entry>HDTV and modern devices, see <xref
linkend="itu709" /></entry>
	    <entry>x&nbsp;=&nbsp;0.640, y&nbsp;=&nbsp;0.330</entry>
	    <entry>x&nbsp;=&nbsp;0.300, y&nbsp;=&nbsp;0.600</entry>
	    <entry>x&nbsp;=&nbsp;0.150, y&nbsp;=&nbsp;0.060</entry>
	    <entry>x&nbsp;=&nbsp;0.3127, y&nbsp;=&nbsp;0.3290,
	    Illuminant D<subscript>65</subscript></entry>
	    <entry>E' = 4.5&nbsp;I&nbsp;for&nbsp;I&nbsp;&le;0.018,
1.099&nbsp;I<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&lt;&nbsp;I</entry>
	    <entry>0.2125&nbsp;E'<subscript>R</subscript>
+&nbsp;0.7154&nbsp;E'<subscript>G</subscript>
+&nbsp;0.0721&nbsp;E'<subscript>B</subscript></entry>
	    <entry>219&nbsp;E'<subscript>Y</subscript>&nbsp;+&nbsp;16</entry>
	    <entry>224&nbsp;P<subscript>B,R</subscript>&nbsp;+&nbsp;128</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_COLORSPACE_BT878</constant></entry>
	    <entry>4</entry>
	    <entry>Broken Bt878 extents<footnote>
		<para>The ubiquitous Bt878 video capture chip
quantizes E'<subscript>Y</subscript> to 238 levels, yielding a range
of Y' = 16 &hellip; 253, unlike Rec. 601 Y' = 16 &hellip;
235. This is not a typo in the Bt878 documentation, it has been
implemented in silicon. The chroma extents are unclear.</para>
	      </footnote>, <xref linkend="itu601" /></entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>0.299&nbsp;E'<subscript>R</subscript>
+&nbsp;0.587&nbsp;E'<subscript>G</subscript>
+&nbsp;0.114&nbsp;E'<subscript>B</subscript></entry>
	    <entry><emphasis>237</emphasis>&nbsp;E'<subscript>Y</subscript>&nbsp;+&nbsp;16</entry>
	    <entry>224&nbsp;P<subscript>B,R</subscript>&nbsp;+&nbsp;128 (probably)</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_COLORSPACE_470_SYSTEM_M</constant></entry>
	    <entry>5</entry>
	    <entry>M/NTSC<footnote>
		<para>No identifier exists for M/PAL which uses
the chromaticities of M/NTSC, the remaining parameters are equal to B and
G/PAL.</para>
	      </footnote> according to <xref linkend="itu470" />, <xref
		linkend="itu601" /></entry>
	    <entry>x&nbsp;=&nbsp;0.67, y&nbsp;=&nbsp;0.33</entry>
	    <entry>x&nbsp;=&nbsp;0.21, y&nbsp;=&nbsp;0.71</entry>
	    <entry>x&nbsp;=&nbsp;0.14, y&nbsp;=&nbsp;0.08</entry>
	    <entry>x&nbsp;=&nbsp;0.310, y&nbsp;=&nbsp;0.316, Illuminant C</entry>
	    <entry>?</entry>
	    <entry>0.299&nbsp;E'<subscript>R</subscript>
+&nbsp;0.587&nbsp;E'<subscript>G</subscript>
+&nbsp;0.114&nbsp;E'<subscript>B</subscript></entry>
	    <entry>219&nbsp;E'<subscript>Y</subscript>&nbsp;+&nbsp;16</entry>
	    <entry>224&nbsp;P<subscript>B,R</subscript>&nbsp;+&nbsp;128</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant></entry>
	    <entry>6</entry>
	    <entry>625-line PAL and SECAM systems according to <xref
linkend="itu470" />, <xref linkend="itu601" /></entry>
	    <entry>x&nbsp;=&nbsp;0.64, y&nbsp;=&nbsp;0.33</entry>
	    <entry>x&nbsp;=&nbsp;0.29, y&nbsp;=&nbsp;0.60</entry>
	    <entry>x&nbsp;=&nbsp;0.15, y&nbsp;=&nbsp;0.06</entry>
	    <entry>x&nbsp;=&nbsp;0.313, y&nbsp;=&nbsp;0.329,
Illuminant D<subscript>65</subscript></entry>
	    <entry>?</entry>
	    <entry>0.299&nbsp;E'<subscript>R</subscript>
+&nbsp;0.587&nbsp;E'<subscript>G</subscript>
+&nbsp;0.114&nbsp;E'<subscript>B</subscript></entry>
	    <entry>219&nbsp;E'<subscript>Y</subscript>&nbsp;+&nbsp;16</entry>
	    <entry>224&nbsp;P<subscript>B,R</subscript>&nbsp;+&nbsp;128</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_COLORSPACE_JPEG</constant></entry>
	    <entry>7</entry>
	    <entry>JPEG Y'CbCr, see <xref linkend="jfif" />, <xref linkend="itu601" /></entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>?</entry>
	    <entry>0.299&nbsp;E'<subscript>R</subscript>
+&nbsp;0.587&nbsp;E'<subscript>G</subscript>
+&nbsp;0.114&nbsp;E'<subscript>B</subscript></entry>
	    <entry>256&nbsp;E'<subscript>Y</subscript>&nbsp;+&nbsp;16<footnote>
		<para>Note JFIF quantizes
Y'P<subscript>B</subscript>P<subscript>R</subscript> in range [0;+1] and
[-0.5;+0.5] to <emphasis>257</emphasis> levels, however Y'CbCr signals
are still clamped to [0;255].</para>
	      </footnote></entry>
	    <entry>256&nbsp;P<subscript>B,R</subscript>&nbsp;+&nbsp;128</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_COLORSPACE_SRGB</constant></entry>
	    <entry>8</entry>
	    <entry>[?]</entry>
	    <entry>x&nbsp;=&nbsp;0.640, y&nbsp;=&nbsp;0.330</entry>
	    <entry>x&nbsp;=&nbsp;0.300, y&nbsp;=&nbsp;0.600</entry>
	    <entry>x&nbsp;=&nbsp;0.150, y&nbsp;=&nbsp;0.060</entry>
	    <entry>x&nbsp;=&nbsp;0.3127, y&nbsp;=&nbsp;0.3290,
	    Illuminant D<subscript>65</subscript></entry>
	    <entry>E' = 4.5&nbsp;I&nbsp;for&nbsp;I&nbsp;&le;0.018,
1.099&nbsp;I<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&lt;&nbsp;I</entry>
	    <entry spanname="spam">n/a</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </section>

  <section id="pixfmt-indexed">
    <title>Indexed Format</title>

    <para>In this format each pixel is represented by an 8 bit index
into a 256 entry ARGB palette. It is intended for <link
linkend="osd">Video Output Overlays</link> only. There are no ioctls to
access the palette, this must be done with ioctls of the Linux framebuffer API.</para>

    <table pgwide="0" frame="none">
      <title>Indexed Image Format</title>
      <tgroup cols="37" align="center">
	<colspec colname="id" align="left" />
	<colspec colname="fourcc" />
	<colspec colname="bit" />

	<colspec colnum="4" colname="b07" align="center" />
	<colspec colnum="5" colname="b06" align="center" />
	<colspec colnum="6" colname="b05" align="center" />
	<colspec colnum="7" colname="b04" align="center" />
	<colspec colnum="8" colname="b03" align="center" />
	<colspec colnum="9" colname="b02" align="center" />
	<colspec colnum="10" colname="b01" align="center" />
	<colspec colnum="11" colname="b00" align="center" />

	<spanspec namest="b07" nameend="b00" spanname="b0" />
	<spanspec namest="b17" nameend="b10" spanname="b1" />
	<spanspec namest="b27" nameend="b20" spanname="b2" />
	<spanspec namest="b37" nameend="b30" spanname="b3" />
	<thead>
	  <row>
	    <entry>Identifier</entry>
	    <entry>Code</entry>
	    <entry>&nbsp;</entry>
	    <entry spanname="b0">Byte&nbsp;0</entry>
	  </row>
	  <row>
	    <entry>&nbsp;</entry>
	    <entry>&nbsp;</entry>
	    <entry>Bit</entry>
	    <entry>7</entry>
	    <entry>6</entry>
	    <entry>5</entry>
	    <entry>4</entry>
	    <entry>3</entry>
	    <entry>2</entry>
	    <entry>1</entry>
	    <entry>0</entry>
	  </row>
	</thead>
	<tbody valign="top">
	  <row id="V4L2-PIX-FMT-PAL8">
	    <entry><constant>V4L2_PIX_FMT_PAL8</constant></entry>
	    <entry>'PAL8'</entry>
	    <entry></entry>
	    <entry>i<subscript>7</subscript></entry>
	    <entry>i<subscript>6</subscript></entry>
	    <entry>i<subscript>5</subscript></entry>
	    <entry>i<subscript>4</subscript></entry>
	    <entry>i<subscript>3</subscript></entry>
	    <entry>i<subscript>2</subscript></entry>
	    <entry>i<subscript>1</subscript></entry>
	    <entry>i<subscript>0</subscript></entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </section>

  <section id="pixfmt-rgb">
    <title>RGB Formats</title>

    &sub-packed-rgb;
    &sub-sbggr8;
    &sub-sgbrg8;
    &sub-sgrbg8;
    &sub-srggb8;
    &sub-sbggr16;
    &sub-srggb10;
  </section>

  <section id="yuv-formats">
    <title>YUV Formats</title>

    <para>YUV is the format native to TV broadcast and composite video
signals. It separates the brightness information (Y) from the color
information (U and V or Cb and Cr). The color information consists of
red and blue <emphasis>color difference</emphasis> signals, this way
the green component can be reconstructed by subtracting from the
brightness component. See <xref linkend="colorspaces" /> for conversion
examples. YUV was chosen because early television would only transmit
brightness information. To add color in a way compatible with existing
receivers a new signal carrier was added to transmit the color
difference signals. Secondary in the YUV format the U and V components
usually have lower resolution than the Y component. This is an analog
video compression technique taking advantage of a property of the
human visual system, being more sensitive to brightness
information.</para>

    &sub-packed-yuv;
    &sub-grey;
    &sub-y10;
    &sub-y12;
    &sub-y10b;
    &sub-y16;
    &sub-yuyv;
    &sub-uyvy;
    &sub-yvyu;
    &sub-vyuy;
    &sub-y41p;
    &sub-yuv420;
    &sub-yuv420m;
    &sub-yuv410;
    &sub-yuv422p;
    &sub-yuv411p;
    &sub-nv12;
    &sub-nv12m;
    &sub-nv12mt;
    &sub-nv16;
    &sub-m420;
  </section>

  <section>
    <title>Compressed Formats</title>

    <table pgwide="1" frame="none" id="compressed-formats">
      <title>Compressed Image Formats</title>
      <tgroup cols="3" align="left">
	&cs-def;
	<thead>
	  <row>
	    <entry>Identifier</entry>
	    <entry>Code</entry>
	    <entry>Details</entry>
	  </row>
	</thead>
	<tbody valign="top">
	 <row id="V4L2-PIX-FMT-JPEG">
	    <entry><constant>V4L2_PIX_FMT_JPEG</constant></entry>
	    <entry>'JPEG'</entry>
	    <entry>TBD. See also &VIDIOC-G-JPEGCOMP;,
	    &VIDIOC-S-JPEGCOMP;.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-MPEG">
	    <entry><constant>V4L2_PIX_FMT_MPEG</constant></entry>
	    <entry>'MPEG'</entry>
	    <entry>MPEG stream. The actual format is determined by
extended control <constant>V4L2_CID_MPEG_STREAM_TYPE</constant>, see
<xref linkend="mpeg-control-id" />.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </section>

  <section id="pixfmt-reserved">
    <title>Reserved Format Identifiers</title>

    <para>These formats are not defined by this specification, they
are just listed for reference and to avoid naming conflicts. If you
want to register your own format, send an e-mail to the linux-media mailing
list &v4l-ml; for inclusion in the <filename>videodev2.h</filename>
file. If you want to share your format with other developers add a
link to your documentation and send a copy to the linux-media mailing list
for inclusion in this section. If you think your format should be listed
in a standard format section please make a proposal on the linux-media mailing
list.</para>

    <table pgwide="1" frame="none" id="reserved-formats">
      <title>Reserved Image Formats</title>
      <tgroup cols="3" align="left">
	&cs-def;
	<thead>
	  <row>
	    <entry>Identifier</entry>
	    <entry>Code</entry>
	    <entry>Details</entry>
	  </row>
	</thead>
	<tbody valign="top">
	  <row id="V4L2-PIX-FMT-DV">
	    <entry><constant>V4L2_PIX_FMT_DV</constant></entry>
	    <entry>'dvsd'</entry>
	    <entry>unknown</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-ET61X251">
	    <entry><constant>V4L2_PIX_FMT_ET61X251</constant></entry>
	    <entry>'E625'</entry>
	    <entry>Compressed format of the ET61X251 driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-HI240">
	    <entry><constant>V4L2_PIX_FMT_HI240</constant></entry>
	    <entry>'HI24'</entry>
	    <entry><para>8 bit RGB format used by the BTTV driver.</para></entry>
	  </row>
	  <row id="V4L2-PIX-FMT-HM12">
	    <entry><constant>V4L2_PIX_FMT_HM12</constant></entry>
	    <entry>'HM12'</entry>
	    <entry><para>YUV 4:2:0 format used by the
IVTV driver, <ulink url="http://www.ivtvdriver.org/">
http://www.ivtvdriver.org/</ulink></para><para>The format is documented in the
kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.hm12</filename>
</para></entry>
	  </row>
	  <row id="V4L2-PIX-FMT-CPIA1">
	    <entry><constant>V4L2_PIX_FMT_CPIA1</constant></entry>
	    <entry>'CPIA'</entry>
	    <entry>YUV format used by the gspca cpia1 driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SPCA501">
	    <entry><constant>V4L2_PIX_FMT_SPCA501</constant></entry>
	    <entry>'S501'</entry>
	    <entry>YUYV per line used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SPCA505">
	    <entry><constant>V4L2_PIX_FMT_SPCA505</constant></entry>
	    <entry>'S505'</entry>
	    <entry>YYUV per line used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SPCA508">
	    <entry><constant>V4L2_PIX_FMT_SPCA508</constant></entry>
	    <entry>'S508'</entry>
	    <entry>YUVY per line used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SPCA561">
	    <entry><constant>V4L2_PIX_FMT_SPCA561</constant></entry>
	    <entry>'S561'</entry>
	    <entry>Compressed GBRG Bayer format used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SGRBG10DPCM8">
	    <entry><constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant></entry>
	    <entry>'DB10'</entry>
	    <entry>10 bit raw Bayer DPCM compressed to 8 bits.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-PAC207">
	    <entry><constant>V4L2_PIX_FMT_PAC207</constant></entry>
	    <entry>'P207'</entry>
	    <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-MR97310A">
	    <entry><constant>V4L2_PIX_FMT_MR97310A</constant></entry>
	    <entry>'M310'</entry>
	    <entry>Compressed BGGR Bayer format used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-OV511">
	    <entry><constant>V4L2_PIX_FMT_OV511</constant></entry>
	    <entry>'O511'</entry>
	    <entry>OV511 JPEG format used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-OV518">
	    <entry><constant>V4L2_PIX_FMT_OV518</constant></entry>
	    <entry>'O518'</entry>
	    <entry>OV518 JPEG format used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-PJPG">
	    <entry><constant>V4L2_PIX_FMT_PJPG</constant></entry>
	    <entry>'PJPG'</entry>
	    <entry>Pixart 73xx JPEG format used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SQ905C">
	    <entry><constant>V4L2_PIX_FMT_SQ905C</constant></entry>
	    <entry>'905C'</entry>
	    <entry>Compressed RGGB bayer format used by the gspca driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-MJPEG">
	    <entry><constant>V4L2_PIX_FMT_MJPEG</constant></entry>
	    <entry>'MJPG'</entry>
	    <entry>Compressed format used by the Zoran driver</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-PWC1">
	    <entry><constant>V4L2_PIX_FMT_PWC1</constant></entry>
	    <entry>'PWC1'</entry>
	    <entry>Compressed format of the PWC driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-PWC2">
	    <entry><constant>V4L2_PIX_FMT_PWC2</constant></entry>
	    <entry>'PWC2'</entry>
	    <entry>Compressed format of the PWC driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SN9C10X">
	    <entry><constant>V4L2_PIX_FMT_SN9C10X</constant></entry>
	    <entry>'S910'</entry>
	    <entry>Compressed format of the SN9C102 driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SN9C20X-I420">
	    <entry><constant>V4L2_PIX_FMT_SN9C20X_I420</constant></entry>
	    <entry>'S920'</entry>
	    <entry>YUV 4:2:0 format of the gspca sn9c20x driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-SN9C2028">
	    <entry><constant>V4L2_PIX_FMT_SN9C2028</constant></entry>
	    <entry>'SONX'</entry>
	    <entry>Compressed GBRG bayer format of the gspca sn9c2028 driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-STV0680">
	    <entry><constant>V4L2_PIX_FMT_STV0680</constant></entry>
	    <entry>'S680'</entry>
	    <entry>Bayer format of the gspca stv0680 driver.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-WNVA">
	    <entry><constant>V4L2_PIX_FMT_WNVA</constant></entry>
	    <entry>'WNVA'</entry>
	    <entry><para>Used by the Winnov Videum driver, <ulink
url="http://www.thedirks.org/winnov/">
http://www.thedirks.org/winnov/</ulink></para></entry>
	  </row>
	  <row id="V4L2-PIX-FMT-TM6000">
	    <entry><constant>V4L2_PIX_FMT_TM6000</constant></entry>
	    <entry>'TM60'</entry>
	    <entry><para>Used by Trident tm6000</para></entry>
	  </row>
	  <row id="V4L2-PIX-FMT-CIT-YYVYUY">
	    <entry><constant>V4L2_PIX_FMT_CIT_YYVYUY</constant></entry>
	    <entry>'CITV'</entry>
	    <entry><para>Used by xirlink CIT, found at IBM webcams.</para>
	           <para>Uses one line of Y then 1 line of VYUY</para>
	    </entry>
	  </row>
	  <row id="V4L2-PIX-FMT-KONICA420">
	    <entry><constant>V4L2_PIX_FMT_KONICA420</constant></entry>
	    <entry>'KONI'</entry>
	    <entry><para>Used by Konica webcams.</para>
	           <para>YUV420 planar in blocks of 256 pixels.</para>
	    </entry>
	  </row>
	  <row id="V4L2-PIX-FMT-YYUV">
	    <entry><constant>V4L2_PIX_FMT_YYUV</constant></entry>
	    <entry>'YYUV'</entry>
	    <entry>unknown</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-Y4">
	    <entry><constant>V4L2_PIX_FMT_Y4</constant></entry>
	    <entry>'Y04 '</entry>
	    <entry>Old 4-bit greyscale format. Only the least significant 4 bits of each byte are used,
the other bits are set to 0.</entry>
	  </row>
	  <row id="V4L2-PIX-FMT-Y6">
	    <entry><constant>V4L2_PIX_FMT_Y6</constant></entry>
	    <entry>'Y06 '</entry>
	    <entry>Old 6-bit greyscale format. Only the least significant 6 bits of each byte are used,
the other bits are set to 0.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </section>

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