--- /dev/null
+<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>
+
+<para>Do not use the multiplanar buffer types. Use <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>
+instead of <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>
+and use <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> instead of
+<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>.</para>
+
+ <para>This ioctl must be implemented for video capture or output devices that
+support cropping and/or scaling and/or have non-square pixels, and for overlay devices.</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> and
+<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. 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 × 480 rectangle for NTSC, a
+768 × 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>__u32</entry>
+ <entry><structfield>width</structfield></entry>
+ <entry>Width of the rectangle, in pixels.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>height</structfield></entry>
+ <entry>Height of the rectangle, in pixels.</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.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+</refentry>
Code Review / kvmfornfv.git / blobdiff