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Diffstat (limited to 'Documentation/DocBook/v4l/vidioc-cropcap.xml')
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diff --git a/Documentation/DocBook/v4l/vidioc-cropcap.xml b/Documentation/DocBook/v4l/vidioc-cropcap.xml new file mode 100644 index 00000000..816e90e2 --- /dev/null +++ b/Documentation/DocBook/v4l/vidioc-cropcap.xml @@ -0,0 +1,174 @@ +<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>&v4l2-buf-type;</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.</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>__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 or the ioctl is not supported. This is not permitted for +video capture, output and overlay devices, which must support +<constant>VIDIOC_CROPCAP</constant>.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> +</refentry> + +<!-- +Local Variables: +mode: sgml +sgml-parent-document: "v4l2.sgml" +indent-tabs-mode: nil +End: +--> |