mirror of https://gitee.com/openkylin/linux.git
802 lines
30 KiB
XML
802 lines
30 KiB
XML
<title>Image Formats</title>
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<para>The V4L2 API was primarily designed for devices exchanging
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image data with applications. The
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<structname>v4l2_pix_format</structname> structure defines the format
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and layout of an image in memory. Image formats are negotiated with
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the &VIDIOC-S-FMT; ioctl. (The explanations here focus on video
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capturing and output, for overlay frame buffer formats see also
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&VIDIOC-G-FBUF;.)</para>
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<table pgwide="1" frame="none" id="v4l2-pix-format">
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<title>struct <structname>v4l2_pix_format</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>width</structfield></entry>
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<entry>Image width in pixels.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>height</structfield></entry>
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<entry>Image height in pixels.</entry>
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</row>
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<row>
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<entry spanname="hspan">Applications set these fields to
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request an image size, drivers return the closest possible values. In
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case of planar formats the <structfield>width</structfield> and
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<structfield>height</structfield> applies to the largest plane. To
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avoid ambiguities drivers must return values rounded up to a multiple
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of the scale factor of any smaller planes. For example when the image
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format is YUV 4:2:0, <structfield>width</structfield> and
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<structfield>height</structfield> must be multiples of two.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>pixelformat</structfield></entry>
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<entry>The pixel format or type of compression, set by the
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application. This is a little endian <link
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linkend="v4l2-fourcc">four character code</link>. V4L2 defines
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standard RGB formats in <xref linkend="rgb-formats" />, YUV formats in <xref
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linkend="yuv-formats" />, and reserved codes in <xref
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linkend="reserved-formats" /></entry>
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</row>
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<row>
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<entry>&v4l2-field;</entry>
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<entry><structfield>field</structfield></entry>
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<entry>Video images are typically interlaced. Applications
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can request to capture or output only the top or bottom field, or both
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fields interlaced or sequentially stored in one buffer or alternating
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in separate buffers. Drivers return the actual field order selected.
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For details see <xref linkend="field-order" />.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>bytesperline</structfield></entry>
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<entry>Distance in bytes between the leftmost pixels in two
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adjacent lines.</entry>
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</row>
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<row>
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<entry spanname="hspan"><para>Both applications and drivers
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can set this field to request padding bytes at the end of each line.
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Drivers however may ignore the value requested by the application,
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returning <structfield>width</structfield> times bytes per pixel or a
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larger value required by the hardware. That implies applications can
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just set this field to zero to get a reasonable
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default.</para><para>Video hardware may access padding bytes,
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therefore they must reside in accessible memory. Consider cases where
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padding bytes after the last line of an image cross a system page
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boundary. Input devices may write padding bytes, the value is
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undefined. Output devices ignore the contents of padding
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bytes.</para><para>When the image format is planar the
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<structfield>bytesperline</structfield> value applies to the largest
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plane and is divided by the same factor as the
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<structfield>width</structfield> field for any smaller planes. For
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example the Cb and Cr planes of a YUV 4:2:0 image have half as many
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padding bytes following each line as the Y plane. To avoid ambiguities
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drivers must return a <structfield>bytesperline</structfield> value
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rounded up to a multiple of the scale factor.</para></entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>sizeimage</structfield></entry>
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<entry>Size in bytes of the buffer to hold a complete image,
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set by the driver. Usually this is
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<structfield>bytesperline</structfield> times
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<structfield>height</structfield>. When the image consists of variable
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length compressed data this is the maximum number of bytes required to
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hold an image.</entry>
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</row>
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<row>
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<entry>&v4l2-colorspace;</entry>
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<entry><structfield>colorspace</structfield></entry>
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<entry>This information supplements the
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<structfield>pixelformat</structfield> and must be set by the driver,
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see <xref linkend="colorspaces" />.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>priv</structfield></entry>
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<entry>Reserved for custom (driver defined) additional
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information about formats. When not used drivers and applications must
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set this field to zero.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<section>
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<title>Standard Image Formats</title>
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<para>In order to exchange images between drivers and
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applications, it is necessary to have standard image data formats
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which both sides will interpret the same way. V4L2 includes several
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such formats, and this section is intended to be an unambiguous
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specification of the standard image data formats in V4L2.</para>
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<para>V4L2 drivers are not limited to these formats, however.
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Driver-specific formats are possible. In that case the application may
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depend on a codec to convert images to one of the standard formats
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when needed. But the data can still be stored and retrieved in the
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proprietary format. For example, a device may support a proprietary
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compressed format. Applications can still capture and save the data in
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the compressed format, saving much disk space, and later use a codec
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to convert the images to the X Windows screen format when the video is
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to be displayed.</para>
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<para>Even so, ultimately, some standard formats are needed, so
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the V4L2 specification would not be complete without well-defined
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standard formats.</para>
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<para>The V4L2 standard formats are mainly uncompressed formats. The
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pixels are always arranged in memory from left to right, and from top
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to bottom. The first byte of data in the image buffer is always for
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the leftmost pixel of the topmost row. Following that is the pixel
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immediately to its right, and so on until the end of the top row of
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pixels. Following the rightmost pixel of the row there may be zero or
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more bytes of padding to guarantee that each row of pixel data has a
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certain alignment. Following the pad bytes, if any, is data for the
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leftmost pixel of the second row from the top, and so on. The last row
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has just as many pad bytes after it as the other rows.</para>
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<para>In V4L2 each format has an identifier which looks like
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<constant>PIX_FMT_XXX</constant>, defined in the <link
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linkend="videodev">videodev.h</link> header file. These identifiers
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represent <link linkend="v4l2-fourcc">four character codes</link>
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which are also listed below, however they are not the same as those
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used in the Windows world.</para>
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</section>
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<section id="colorspaces">
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<title>Colorspaces</title>
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<para>[intro]</para>
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<!-- See proposal by Billy Biggs, video4linux-list@redhat.com
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on 11 Oct 2002, subject: "Re: [V4L] Re: v4l2 api", and
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http://vektor.theorem.ca/graphics/ycbcr/ and
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http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html -->
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<para>
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<variablelist>
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<varlistentry>
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<term>Gamma Correction</term>
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<listitem>
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<para>[to do]</para>
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<para>E'<subscript>R</subscript> = f(R)</para>
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<para>E'<subscript>G</subscript> = f(G)</para>
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<para>E'<subscript>B</subscript> = f(B)</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Construction of luminance and color-difference
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signals</term>
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<listitem>
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<para>[to do]</para>
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<para>E'<subscript>Y</subscript> =
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Coeff<subscript>R</subscript> E'<subscript>R</subscript>
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+ Coeff<subscript>G</subscript> E'<subscript>G</subscript>
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+ Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
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<para>(E'<subscript>R</subscript> - E'<subscript>Y</subscript>) = E'<subscript>R</subscript>
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- Coeff<subscript>R</subscript> E'<subscript>R</subscript>
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- Coeff<subscript>G</subscript> E'<subscript>G</subscript>
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- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
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<para>(E'<subscript>B</subscript> - E'<subscript>Y</subscript>) = E'<subscript>B</subscript>
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- Coeff<subscript>R</subscript> E'<subscript>R</subscript>
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- Coeff<subscript>G</subscript> E'<subscript>G</subscript>
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- Coeff<subscript>B</subscript> E'<subscript>B</subscript></para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Re-normalized color-difference signals</term>
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<listitem>
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<para>The color-difference signals are scaled back to unity
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range [-0.5;+0.5]:</para>
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<para>K<subscript>B</subscript> = 0.5 / (1 - Coeff<subscript>B</subscript>)</para>
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<para>K<subscript>R</subscript> = 0.5 / (1 - Coeff<subscript>R</subscript>)</para>
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<para>P<subscript>B</subscript> =
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K<subscript>B</subscript> (E'<subscript>B</subscript> - E'<subscript>Y</subscript>) =
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0.5 (Coeff<subscript>R</subscript> / Coeff<subscript>B</subscript>) E'<subscript>R</subscript>
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+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>B</subscript>) E'<subscript>G</subscript>
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+ 0.5 E'<subscript>B</subscript></para>
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<para>P<subscript>R</subscript> =
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K<subscript>R</subscript> (E'<subscript>R</subscript> - E'<subscript>Y</subscript>) =
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0.5 E'<subscript>R</subscript>
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+ 0.5 (Coeff<subscript>G</subscript> / Coeff<subscript>R</subscript>) E'<subscript>G</subscript>
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+ 0.5 (Coeff<subscript>B</subscript> / Coeff<subscript>R</subscript>) E'<subscript>B</subscript></para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>Quantization</term>
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<listitem>
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<para>[to do]</para>
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<para>Y' = (Lum. Levels - 1) · E'<subscript>Y</subscript> + Lum. Offset</para>
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<para>C<subscript>B</subscript> = (Chrom. Levels - 1)
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· P<subscript>B</subscript> + Chrom. Offset</para>
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<para>C<subscript>R</subscript> = (Chrom. Levels - 1)
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· P<subscript>R</subscript> + Chrom. Offset</para>
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<para>Rounding to the nearest integer and clamping to the range
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[0;255] finally yields the digital color components Y'CbCr
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stored in YUV images.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<example>
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<title>ITU-R Rec. BT.601 color conversion</title>
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<para>Forward Transformation</para>
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<programlisting>
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int ER, EG, EB; /* gamma corrected RGB input [0;255] */
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int Y1, Cb, Cr; /* output [0;255] */
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double r, g, b; /* temporaries */
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double y1, pb, pr;
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int
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clamp (double x)
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{
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int r = x; /* round to nearest */
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if (r < 0) return 0;
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else if (r > 255) return 255;
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else return r;
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}
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r = ER / 255.0;
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g = EG / 255.0;
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b = EB / 255.0;
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y1 = 0.299 * r + 0.587 * g + 0.114 * b;
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pb = -0.169 * r - 0.331 * g + 0.5 * b;
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pr = 0.5 * r - 0.419 * g - 0.081 * b;
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Y1 = clamp (219 * y1 + 16);
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Cb = clamp (224 * pb + 128);
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Cr = clamp (224 * pr + 128);
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/* or shorter */
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y1 = 0.299 * ER + 0.587 * EG + 0.114 * EB;
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Y1 = clamp ( (219 / 255.0) * y1 + 16);
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Cb = clamp (((224 / 255.0) / (2 - 2 * 0.114)) * (EB - y1) + 128);
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Cr = clamp (((224 / 255.0) / (2 - 2 * 0.299)) * (ER - y1) + 128);
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</programlisting>
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<para>Inverse Transformation</para>
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<programlisting>
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int Y1, Cb, Cr; /* gamma pre-corrected input [0;255] */
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int ER, EG, EB; /* output [0;255] */
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double r, g, b; /* temporaries */
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double y1, pb, pr;
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int
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clamp (double x)
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{
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int r = x; /* round to nearest */
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if (r < 0) return 0;
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else if (r > 255) return 255;
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else return r;
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}
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y1 = (255 / 219.0) * (Y1 - 16);
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pb = (255 / 224.0) * (Cb - 128);
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pr = (255 / 224.0) * (Cr - 128);
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r = 1.0 * y1 + 0 * pb + 1.402 * pr;
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g = 1.0 * y1 - 0.344 * pb - 0.714 * pr;
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b = 1.0 * y1 + 1.772 * pb + 0 * pr;
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ER = clamp (r * 255); /* [ok? one should prob. limit y1,pb,pr] */
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EG = clamp (g * 255);
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EB = clamp (b * 255);
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</programlisting>
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</example>
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<table pgwide="1" id="v4l2-colorspace" orient="land">
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<title>enum v4l2_colorspace</title>
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<tgroup cols="11" align="center">
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<colspec align="left" />
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<colspec align="center" />
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<colspec align="left" />
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<colspec colname="cr" />
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<colspec colname="cg" />
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<colspec colname="cb" />
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<colspec colname="wp" />
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<colspec colname="gc" />
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<colspec colname="lum" />
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<colspec colname="qy" />
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<colspec colname="qc" />
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<spanspec namest="cr" nameend="cb" spanname="chrom" />
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<spanspec namest="qy" nameend="qc" spanname="quant" />
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<spanspec namest="lum" nameend="qc" spanname="spam" />
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<thead>
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<row>
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<entry morerows="1">Identifier</entry>
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<entry morerows="1">Value</entry>
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<entry morerows="1">Description</entry>
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<entry spanname="chrom">Chromaticities<footnote>
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<para>The coordinates of the color primaries are
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given in the CIE system (1931)</para>
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</footnote></entry>
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<entry morerows="1">White Point</entry>
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<entry morerows="1">Gamma Correction</entry>
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<entry morerows="1">Luminance E'<subscript>Y</subscript></entry>
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<entry spanname="quant">Quantization</entry>
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</row>
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<row>
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<entry>Red</entry>
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<entry>Green</entry>
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<entry>Blue</entry>
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<entry>Y'</entry>
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<entry>Cb, Cr</entry>
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</row>
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</thead>
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_COLORSPACE_SMPTE170M</constant></entry>
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<entry>1</entry>
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<entry>NTSC/PAL according to <xref linkend="smpte170m" />,
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<xref linkend="itu601" /></entry>
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<entry>x = 0.630, y = 0.340</entry>
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<entry>x = 0.310, y = 0.595</entry>
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<entry>x = 0.155, y = 0.070</entry>
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<entry>x = 0.3127, y = 0.3290,
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Illuminant D<subscript>65</subscript></entry>
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<entry>E' = 4.5 I for I ≤0.018,
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1.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry>
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<entry>0.299 E'<subscript>R</subscript>
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+ 0.587 E'<subscript>G</subscript>
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+ 0.114 E'<subscript>B</subscript></entry>
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<entry>219 E'<subscript>Y</subscript> + 16</entry>
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<entry>224 P<subscript>B,R</subscript> + 128</entry>
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</row>
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<row>
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<entry><constant>V4L2_COLORSPACE_SMPTE240M</constant></entry>
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<entry>2</entry>
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<entry>1125-Line (US) HDTV, see <xref
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linkend="smpte240m" /></entry>
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<entry>x = 0.630, y = 0.340</entry>
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<entry>x = 0.310, y = 0.595</entry>
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<entry>x = 0.155, y = 0.070</entry>
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<entry>x = 0.3127, y = 0.3290,
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Illuminant D<subscript>65</subscript></entry>
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<entry>E' = 4 I for I ≤0.0228,
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1.1115 I<superscript>0.45</superscript> - 0.1115 for 0.0228 < I</entry>
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<entry>0.212 E'<subscript>R</subscript>
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+ 0.701 E'<subscript>G</subscript>
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+ 0.087 E'<subscript>B</subscript></entry>
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<entry>219 E'<subscript>Y</subscript> + 16</entry>
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<entry>224 P<subscript>B,R</subscript> + 128</entry>
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</row>
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<row>
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<entry><constant>V4L2_COLORSPACE_REC709</constant></entry>
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<entry>3</entry>
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<entry>HDTV and modern devices, see <xref
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linkend="itu709" /></entry>
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<entry>x = 0.640, y = 0.330</entry>
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<entry>x = 0.300, y = 0.600</entry>
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<entry>x = 0.150, y = 0.060</entry>
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<entry>x = 0.3127, y = 0.3290,
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Illuminant D<subscript>65</subscript></entry>
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<entry>E' = 4.5 I for I ≤0.018,
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1.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < I</entry>
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<entry>0.2125 E'<subscript>R</subscript>
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+ 0.7154 E'<subscript>G</subscript>
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+ 0.0721 E'<subscript>B</subscript></entry>
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<entry>219 E'<subscript>Y</subscript> + 16</entry>
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<entry>224 P<subscript>B,R</subscript> + 128</entry>
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</row>
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<row>
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<entry><constant>V4L2_COLORSPACE_BT878</constant></entry>
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<entry>4</entry>
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<entry>Broken Bt878 extents<footnote>
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<para>The ubiquitous Bt878 video capture chip
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quantizes E'<subscript>Y</subscript> to 238 levels, yielding a range
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of Y' = 16 … 253, unlike Rec. 601 Y' = 16 …
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235. This is not a typo in the Bt878 documentation, it has been
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implemented in silicon. The chroma extents are unclear.</para>
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</footnote>, <xref linkend="itu601" /></entry>
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<entry>?</entry>
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<entry>?</entry>
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<entry>?</entry>
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<entry>?</entry>
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<entry>?</entry>
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|
<entry>0.299 E'<subscript>R</subscript>
|
|
+ 0.587 E'<subscript>G</subscript>
|
|
+ 0.114 E'<subscript>B</subscript></entry>
|
|
<entry><emphasis>237</emphasis> E'<subscript>Y</subscript> + 16</entry>
|
|
<entry>224 P<subscript>B,R</subscript> + 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 = 0.67, y = 0.33</entry>
|
|
<entry>x = 0.21, y = 0.71</entry>
|
|
<entry>x = 0.14, y = 0.08</entry>
|
|
<entry>x = 0.310, y = 0.316, Illuminant C</entry>
|
|
<entry>?</entry>
|
|
<entry>0.299 E'<subscript>R</subscript>
|
|
+ 0.587 E'<subscript>G</subscript>
|
|
+ 0.114 E'<subscript>B</subscript></entry>
|
|
<entry>219 E'<subscript>Y</subscript> + 16</entry>
|
|
<entry>224 P<subscript>B,R</subscript> + 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 = 0.64, y = 0.33</entry>
|
|
<entry>x = 0.29, y = 0.60</entry>
|
|
<entry>x = 0.15, y = 0.06</entry>
|
|
<entry>x = 0.313, y = 0.329,
|
|
Illuminant D<subscript>65</subscript></entry>
|
|
<entry>?</entry>
|
|
<entry>0.299 E'<subscript>R</subscript>
|
|
+ 0.587 E'<subscript>G</subscript>
|
|
+ 0.114 E'<subscript>B</subscript></entry>
|
|
<entry>219 E'<subscript>Y</subscript> + 16</entry>
|
|
<entry>224 P<subscript>B,R</subscript> + 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 E'<subscript>R</subscript>
|
|
+ 0.587 E'<subscript>G</subscript>
|
|
+ 0.114 E'<subscript>B</subscript></entry>
|
|
<entry>256 E'<subscript>Y</subscript> + 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 P<subscript>B,R</subscript> + 128</entry>
|
|
</row>
|
|
<row>
|
|
<entry><constant>V4L2_COLORSPACE_SRGB</constant></entry>
|
|
<entry>8</entry>
|
|
<entry>[?]</entry>
|
|
<entry>x = 0.640, y = 0.330</entry>
|
|
<entry>x = 0.300, y = 0.600</entry>
|
|
<entry>x = 0.150, y = 0.060</entry>
|
|
<entry>x = 0.3127, y = 0.3290,
|
|
Illuminant D<subscript>65</subscript></entry>
|
|
<entry>E' = 4.5 I for I ≤0.018,
|
|
1.099 I<superscript>0.45</superscript> - 0.099 for 0.018 < 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> </entry>
|
|
<entry spanname="b0">Byte 0</entry>
|
|
</row>
|
|
<row>
|
|
<entry> </entry>
|
|
<entry> </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-sbggr16;
|
|
</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-y16;
|
|
&sub-yuyv;
|
|
&sub-uyvy;
|
|
&sub-yvyu;
|
|
&sub-vyuy;
|
|
&sub-y41p;
|
|
&sub-yuv420;
|
|
&sub-yuv410;
|
|
&sub-yuv422p;
|
|
&sub-yuv411p;
|
|
&sub-nv12;
|
|
&sub-nv16;
|
|
</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-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-SGRBG10">
|
|
<entry><constant>V4L2_PIX_FMT_SGRBG10</constant></entry>
|
|
<entry>'DA10'</entry>
|
|
<entry>10 bit raw Bayer, expanded to 16 bits.</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-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-YYUV">
|
|
<entry><constant>V4L2_PIX_FMT_YYUV</constant></entry>
|
|
<entry>'YYUV'</entry>
|
|
<entry>unknown</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</section>
|
|
|
|
<!--
|
|
Local Variables:
|
|
mode: sgml
|
|
sgml-parent-document: "v4l2.sgml"
|
|
indent-tabs-mode: nil
|
|
End:
|
|
-->
|