Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
1 <refentry id="vidioc-cropcap"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_CROPCAP</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_CROPCAP</refname> 9 <refpurpose>Information about the video cropping and scaling abilities</refpurpose> 10 </refnamediv> 11 12 <refsynopsisdiv> 13 <funcsynopsis> 14 <funcprototype> 15 <funcdef>int <function>ioctl</function></funcdef> 16 <paramdef>int <parameter>fd</parameter></paramdef> 17 <paramdef>int <parameter>request</parameter></paramdef> 18 <paramdef>struct v4l2_cropcap 19 *<parameter>argp</parameter></paramdef> 20 </funcprototype> 21 </funcsynopsis> 22 </refsynopsisdiv> 23 24 <refsect1> 25 <title>Arguments</title> 26 27 <variablelist> 28 <varlistentry> 29 <term><parameter>fd</parameter></term> 30 <listitem> 31 <para>&fd;</para> 32 </listitem> 33 </varlistentry> 34 <varlistentry> 35 <term><parameter>request</parameter></term> 36 <listitem> 37 <para>VIDIOC_CROPCAP</para> 38 </listitem> 39 </varlistentry> 40 <varlistentry> 41 <term><parameter>argp</parameter></term> 42 <listitem> 43 <para></para> 44 </listitem> 45 </varlistentry> 46 </variablelist> 47 </refsect1> 48 49 <refsect1> 50 <title>Description</title> 51 52 <para>Applications use this function to query the cropping 53 limits, the pixel aspect of images and to calculate scale factors. 54 They set the <structfield>type</structfield> field of a v4l2_cropcap 55 structure to the respective buffer (stream) type and call the 56 <constant>VIDIOC_CROPCAP</constant> ioctl with a pointer to this 57 structure. Drivers fill the rest of the structure. The results are 58 constant except when switching the video standard. Remember this 59 switch can occur implicit when switching the video input or 60 output.</para> 61 62 <para>Do not use the multiplanar buffer types. Use <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant> 63 instead of <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant> 64 and use <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> instead of 65 <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>.</para> 66 67 <para>This ioctl must be implemented for video capture or output devices that 68 support cropping and/or scaling and/or have non-square pixels, and for overlay devices.</para> 69 70 <table pgwide="1" frame="none" id="v4l2-cropcap"> 71 <title>struct <structname>v4l2_cropcap</structname></title> 72 <tgroup cols="3"> 73 &cs-str; 74 <tbody valign="top"> 75 <row> 76 <entry>__u32</entry> 77 <entry><structfield>type</structfield></entry> 78 <entry>Type of the data stream, set by the application. 79 Only these types are valid here: 80 <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>, 81 <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant> and 82 <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry> 83 </row> 84 <row> 85 <entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry> 86 <entry><structfield>bounds</structfield></entry> 87 <entry>Defines the window within capturing or output is 88 possible, this may exclude for example the horizontal and vertical 89 blanking areas. The cropping rectangle cannot exceed these limits. 90 Width and height are defined in pixels, the driver writer is free to 91 choose origin and units of the coordinate system in the analog 92 domain.</entry> 93 </row> 94 <row> 95 <entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry> 96 <entry><structfield>defrect</structfield></entry> 97 <entry>Default cropping rectangle, it shall cover the 98 "whole picture". Assuming pixel aspect 1/1 this could be for example a 99 640 × 480 rectangle for NTSC, a 100 768 × 576 rectangle for PAL and SECAM centered over 101 the active picture area. The same co-ordinate system as for 102 <structfield>bounds</structfield> is used.</entry> 103 </row> 104 <row> 105 <entry>&v4l2-fract;</entry> 106 <entry><structfield>pixelaspect</structfield></entry> 107 <entry><para>This is the pixel aspect (y / x) when no 108 scaling is applied, the ratio of the actual sampling 109 frequency and the frequency required to get square 110 pixels.</para><para>When cropping coordinates refer to square pixels, 111 the driver sets <structfield>pixelaspect</structfield> to 1/1. Other 112 common values are 54/59 for PAL and SECAM, 11/10 for NTSC sampled 113 according to [<xref linkend="itu601" />].</para></entry> 114 </row> 115 </tbody> 116 </tgroup> 117 </table> 118 119 <!-- NB this table is duplicated in the overlay chapter. --> 120 121 <table pgwide="1" frame="none" id="v4l2-rect-crop"> 122 <title>struct <structname>v4l2_rect</structname></title> 123 <tgroup cols="3"> 124 &cs-str; 125 <tbody valign="top"> 126 <row> 127 <entry>__s32</entry> 128 <entry><structfield>left</structfield></entry> 129 <entry>Horizontal offset of the top, left corner of the 130 rectangle, in pixels.</entry> 131 </row> 132 <row> 133 <entry>__s32</entry> 134 <entry><structfield>top</structfield></entry> 135 <entry>Vertical offset of the top, left corner of the 136 rectangle, in pixels.</entry> 137 </row> 138 <row> 139 <entry>__u32</entry> 140 <entry><structfield>width</structfield></entry> 141 <entry>Width of the rectangle, in pixels.</entry> 142 </row> 143 <row> 144 <entry>__u32</entry> 145 <entry><structfield>height</structfield></entry> 146 <entry>Height of the rectangle, in pixels.</entry> 147 </row> 148 </tbody> 149 </tgroup> 150 </table> 151 </refsect1> 152 153 <refsect1> 154 &return-value; 155 156 <variablelist> 157 <varlistentry> 158 <term><errorcode>EINVAL</errorcode></term> 159 <listitem> 160 <para>The &v4l2-cropcap; <structfield>type</structfield> is 161 invalid.</para> 162 </listitem> 163 </varlistentry> 164 </variablelist> 165 </refsect1> 166 </refentry>
