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 53limits, the pixel aspect of images and to calculate scale factors. 54They set the <structfield>type</structfield> field of a v4l2_cropcap 55structure to the respective buffer (stream) type and call the 56<constant>VIDIOC_CROPCAP</constant> ioctl with a pointer to this 57structure. Drivers fill the rest of the structure. The results are 58constant except when switching the video standard. Remember this 59switch can occur implicit when switching the video input or 60output.</para> 61 62 <para>This ioctl must be implemented for video capture or output devices that 63support cropping and/or scaling and/or have non-square pixels, and for overlay devices.</para> 64 65 <table pgwide="1" frame="none" id="v4l2-cropcap"> 66 <title>struct <structname>v4l2_cropcap</structname></title> 67 <tgroup cols="3"> 68 &cs-str; 69 <tbody valign="top"> 70 <row> 71 <entry>__u32</entry> 72 <entry><structfield>type</structfield></entry> 73 <entry>Type of the data stream, set by the application. 74Only these types are valid here: 75<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>, 76<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>, 77<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>, 78<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant> and 79<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry> 80 </row> 81 <row> 82 <entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry> 83 <entry><structfield>bounds</structfield></entry> 84 <entry>Defines the window within capturing or output is 85possible, this may exclude for example the horizontal and vertical 86blanking areas. The cropping rectangle cannot exceed these limits. 87Width and height are defined in pixels, the driver writer is free to 88choose origin and units of the coordinate system in the analog 89domain.</entry> 90 </row> 91 <row> 92 <entry>struct <link linkend="v4l2-rect-crop">v4l2_rect</link></entry> 93 <entry><structfield>defrect</structfield></entry> 94 <entry>Default cropping rectangle, it shall cover the 95"whole picture". Assuming pixel aspect 1/1 this could be for example a 96640 × 480 rectangle for NTSC, a 97768 × 576 rectangle for PAL and SECAM centered over 98the active picture area. The same co-ordinate system as for 99 <structfield>bounds</structfield> is used.</entry> 100 </row> 101 <row> 102 <entry>&v4l2-fract;</entry> 103 <entry><structfield>pixelaspect</structfield></entry> 104 <entry><para>This is the pixel aspect (y / x) when no 105scaling is applied, the ratio of the actual sampling 106frequency and the frequency required to get square 107pixels.</para><para>When cropping coordinates refer to square pixels, 108the driver sets <structfield>pixelaspect</structfield> to 1/1. Other 109common values are 54/59 for PAL and SECAM, 11/10 for NTSC sampled 110according to [<xref linkend="itu601" />].</para></entry> 111 </row> 112 </tbody> 113 </tgroup> 114 </table> 115 116 <!-- NB this table is duplicated in the overlay chapter. --> 117 118 <table pgwide="1" frame="none" id="v4l2-rect-crop"> 119 <title>struct <structname>v4l2_rect</structname></title> 120 <tgroup cols="3"> 121 &cs-str; 122 <tbody valign="top"> 123 <row> 124 <entry>__s32</entry> 125 <entry><structfield>left</structfield></entry> 126 <entry>Horizontal offset of the top, left corner of the 127rectangle, in pixels.</entry> 128 </row> 129 <row> 130 <entry>__s32</entry> 131 <entry><structfield>top</structfield></entry> 132 <entry>Vertical offset of the top, left corner of the 133rectangle, in pixels.</entry> 134 </row> 135 <row> 136 <entry>__u32</entry> 137 <entry><structfield>width</structfield></entry> 138 <entry>Width of the rectangle, in pixels.</entry> 139 </row> 140 <row> 141 <entry>__u32</entry> 142 <entry><structfield>height</structfield></entry> 143 <entry>Height of the rectangle, in pixels.</entry> 144 </row> 145 </tbody> 146 </tgroup> 147 </table> 148 </refsect1> 149 150 <refsect1> 151 &return-value; 152 153 <variablelist> 154 <varlistentry> 155 <term><errorcode>EINVAL</errorcode></term> 156 <listitem> 157 <para>The &v4l2-cropcap; <structfield>type</structfield> is 158invalid.</para> 159 </listitem> 160 </varlistentry> 161 </variablelist> 162 </refsect1> 163</refentry> 164