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-<refentry id="vidioc-cropcap">
- <refmeta>
- <refentrytitle>ioctl VIDIOC_CROPCAP</refentrytitle>
- &manvol;
- </refmeta>
-
- <refnamediv>
- <refname>VIDIOC_CROPCAP</refname>
- <refpurpose>Information about the video cropping and scaling abilities</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcprototype>
- <funcdef>int <function>ioctl</function></funcdef>
- <paramdef>int <parameter>fd</parameter></paramdef>
- <paramdef>int <parameter>request</parameter></paramdef>
- <paramdef>struct v4l2_cropcap
-*<parameter>argp</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Arguments</title>
-
- <variablelist>
- <varlistentry>
- <term><parameter>fd</parameter></term>
- <listitem>
- <para>&fd;</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>request</parameter></term>
- <listitem>
- <para>VIDIOC_CROPCAP</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>argp</parameter></term>
- <listitem>
- <para></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>Description</title>
-
- <para>Applications use this function to query the cropping
-limits, the pixel aspect of images and to calculate scale factors.
-They set the <structfield>type</structfield> field of a v4l2_cropcap
-structure to the respective buffer (stream) type and call the
-<constant>VIDIOC_CROPCAP</constant> ioctl with a pointer to this
-structure. Drivers fill the rest of the structure. The results are
-constant except when switching the video standard. Remember this
-switch can occur implicit when switching the video input or
-output.</para>
-
- <table pgwide="1" frame="none" id="v4l2-cropcap">
- <title>struct <structname>v4l2_cropcap</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>type</structfield></entry>
- <entry>Type of the data stream, set by the application.
-Only these types are valid here:
-<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
-<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>,
-<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>, and custom (driver
-defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant>
-and higher. See <xref linkend="v4l2-buf-type" />.</entry>
- </row>
- <row>
- <entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry>
- <entry><structfield>bounds</structfield></entry>
- <entry>Defines the window within capturing or output is
-possible, this may exclude for example the horizontal and vertical
-blanking areas. The cropping rectangle cannot exceed these limits.
-Width and height are defined in pixels, the driver writer is free to
-choose origin and units of the coordinate system in the analog
-domain.</entry>
- </row>
- <row>
- <entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry>
- <entry><structfield>defrect</structfield></entry>
- <entry>Default cropping rectangle, it shall cover the
-"whole picture". Assuming pixel aspect 1/1 this could be for example a
-640&nbsp;&times;&nbsp;480 rectangle for NTSC, a
-768&nbsp;&times;&nbsp;576 rectangle for PAL and SECAM centered over
-the active picture area. The same co-ordinate system as for
- <structfield>bounds</structfield> is used.</entry>
- </row>
- <row>
- <entry>&v4l2-fract;</entry>
- <entry><structfield>pixelaspect</structfield></entry>
- <entry><para>This is the pixel aspect (y / x) when no
-scaling is applied, the ratio of the actual sampling
-frequency and the frequency required to get square
-pixels.</para><para>When cropping coordinates refer to square pixels,
-the driver sets <structfield>pixelaspect</structfield> to 1/1. Other
-common values are 54/59 for PAL and SECAM, 11/10 for NTSC sampled
-according to [<xref linkend="itu601" />].</para></entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <!-- NB this table is duplicated in the overlay chapter. -->
-
- <table pgwide="1" frame="none" id="v4l2-rect-crop">
- <title>struct <structname>v4l2_rect</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>__s32</entry>
- <entry><structfield>left</structfield></entry>
- <entry>Horizontal offset of the top, left corner of the
-rectangle, in pixels.</entry>
- </row>
- <row>
- <entry>__s32</entry>
- <entry><structfield>top</structfield></entry>
- <entry>Vertical offset of the top, left corner of the
-rectangle, in pixels.</entry>
- </row>
- <row>
- <entry>__s32</entry>
- <entry><structfield>width</structfield></entry>
- <entry>Width of the rectangle, in pixels.</entry>
- </row>
- <row>
- <entry>__s32</entry>
- <entry><structfield>height</structfield></entry>
- <entry>Height of the rectangle, in pixels. Width
-and height cannot be negative, the fields are signed for
-hysterical reasons. <!-- video4linux-list@redhat.com
-on 22 Oct 2002 subject "Re:[V4L][patches!] Re:v4l2/kernel-2.5" -->
-</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
-
- <refsect1>
- &return-value;
-
- <variablelist>
- <varlistentry>
- <term><errorcode>EINVAL</errorcode></term>
- <listitem>
- <para>The &v4l2-cropcap; <structfield>type</structfield> is
-invalid. This is not permitted for video capture, output and overlay devices,
-which must support <constant>VIDIOC_CROPCAP</constant>.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-</refentry>