1<refentry id="vidioc-g-crop">
2  <refmeta>
3    <refentrytitle>ioctl VIDIOC_G_CROP, VIDIOC_S_CROP</refentrytitle>
4    &manvol;
5  </refmeta>
6
7  <refnamediv>
8    <refname>VIDIOC_G_CROP</refname>
9    <refname>VIDIOC_S_CROP</refname>
10    <refpurpose>Get or set the current cropping rectangle</refpurpose>
11  </refnamediv>
12
13  <refsynopsisdiv>
14    <funcsynopsis>
15      <funcprototype>
16	<funcdef>int <function>ioctl</function></funcdef>
17	<paramdef>int <parameter>fd</parameter></paramdef>
18	<paramdef>int <parameter>request</parameter></paramdef>
19	<paramdef>struct v4l2_crop *<parameter>argp</parameter></paramdef>
20      </funcprototype>
21    </funcsynopsis>
22    <funcsynopsis>
23      <funcprototype>
24	<funcdef>int <function>ioctl</function></funcdef>
25	<paramdef>int <parameter>fd</parameter></paramdef>
26	<paramdef>int <parameter>request</parameter></paramdef>
27	<paramdef>const struct v4l2_crop *<parameter>argp</parameter></paramdef>
28      </funcprototype>
29    </funcsynopsis>
30  </refsynopsisdiv>
31
32  <refsect1>
33    <title>Arguments</title>
34
35    <variablelist>
36      <varlistentry>
37	<term><parameter>fd</parameter></term>
38	<listitem>
39	  <para>&fd;</para>
40	</listitem>
41      </varlistentry>
42      <varlistentry>
43	<term><parameter>request</parameter></term>
44	<listitem>
45	  <para>VIDIOC_G_CROP, VIDIOC_S_CROP</para>
46	</listitem>
47      </varlistentry>
48      <varlistentry>
49	<term><parameter>argp</parameter></term>
50	<listitem>
51	  <para></para>
52	</listitem>
53      </varlistentry>
54    </variablelist>
55  </refsect1>
56
57  <refsect1>
58    <title>Description</title>
59
60    <para>To query the cropping rectangle size and position
61applications set the <structfield>type</structfield> field of a
62<structname>v4l2_crop</structname> structure to the respective buffer
63(stream) type and call the <constant>VIDIOC_G_CROP</constant> ioctl
64with a pointer to this structure. The driver fills the rest of the
65structure or returns the &EINVAL; if cropping is not supported.</para>
66
67    <para>To change the cropping rectangle applications initialize the
68<structfield>type</structfield> and &v4l2-rect; substructure named
69<structfield>c</structfield> of a v4l2_crop structure and call the
70<constant>VIDIOC_S_CROP</constant> ioctl with a pointer to this
71structure.</para>
72
73<para>Do not use the multiplanar buffer types.  Use <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>
74instead of <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>
75and use <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> instead of
76<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>.</para>
77
78    <para>The driver first adjusts the requested dimensions against
79hardware limits, &ie; the bounds given by the capture/output window,
80and it rounds to the closest possible values of horizontal and
81vertical offset, width and height. In particular the driver must round
82the vertical offset of the cropping rectangle to frame lines modulo
83two, such that the field order cannot be confused.</para>
84
85    <para>Second the driver adjusts the image size (the opposite
86rectangle of the scaling process, source or target depending on the
87data direction) to the closest size possible while maintaining the
88current horizontal and vertical scaling factor.</para>
89
90    <para>Finally the driver programs the hardware with the actual
91cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a
92write-only ioctl, it does not return the actual parameters. To query
93them applications must call <constant>VIDIOC_G_CROP</constant> and
94&VIDIOC-G-FMT;. When the parameters are unsuitable the application may
95modify the cropping or image parameters and repeat the cycle until
96satisfactory parameters have been negotiated.</para>
97
98    <para>When cropping is not supported then no parameters are
99changed and <constant>VIDIOC_S_CROP</constant> returns the
100&EINVAL;.</para>
101
102    <table pgwide="1" frame="none" id="v4l2-crop">
103      <title>struct <structname>v4l2_crop</structname></title>
104      <tgroup cols="3">
105	&cs-str;
106	<tbody valign="top">
107	  <row>
108	    <entry>__u32</entry>
109	    <entry><structfield>type</structfield></entry>
110	    <entry>Type of the data stream, set by the application.
111Only these types are valid here: <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
112<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> and
113<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry>
114	  </row>
115	  <row>
116	    <entry>&v4l2-rect;</entry>
117	    <entry><structfield>c</structfield></entry>
118	    <entry>Cropping rectangle. The same co-ordinate system as
119for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry>
120	  </row>
121	</tbody>
122      </tgroup>
123    </table>
124  </refsect1>
125
126  <refsect1>
127    &return-value;
128  </refsect1>
129</refentry>
130