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Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-g-crop.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-g-crop.xml | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-g-crop.xml b/Documentation/DocBook/media/v4l/vidioc-g-crop.xml new file mode 100644 index 000000000000..01a50640dce0 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-g-crop.xml @@ -0,0 +1,126 @@ +<refentry id="vidioc-g-crop"> + <refmeta> + <refentrytitle>ioctl VIDIOC_G_CROP, VIDIOC_S_CROP</refentrytitle> + &manvol; + </refmeta> + + <refnamediv> + <refname>VIDIOC_G_CROP</refname> + <refname>VIDIOC_S_CROP</refname> + <refpurpose>Get or set the current cropping rectangle</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_crop *<parameter>argp</parameter></paramdef> + </funcprototype> + </funcsynopsis> + <funcsynopsis> + <funcprototype> + <funcdef>int <function>ioctl</function></funcdef> + <paramdef>int <parameter>fd</parameter></paramdef> + <paramdef>int <parameter>request</parameter></paramdef> + <paramdef>const struct v4l2_crop *<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_G_CROP, VIDIOC_S_CROP</para> + </listitem> + </varlistentry> + <varlistentry> + <term><parameter>argp</parameter></term> + <listitem> + <para></para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Description</title> + + <para>To query the cropping rectangle size and position +applications set the <structfield>type</structfield> field of a +<structname>v4l2_crop</structname> structure to the respective buffer +(stream) type and call the <constant>VIDIOC_G_CROP</constant> ioctl +with a pointer to this structure. The driver fills the rest of the +structure or returns the &EINVAL; if cropping is not supported.</para> + + <para>To change the cropping rectangle applications initialize the +<structfield>type</structfield> and &v4l2-rect; substructure named +<structfield>c</structfield> of a v4l2_crop structure and call the +<constant>VIDIOC_S_CROP</constant> ioctl with a pointer to this +structure.</para> + + <para>The driver first adjusts the requested dimensions against +hardware limits, &ie; the bounds given by the capture/output window, +and it rounds to the closest possible values of horizontal and +vertical offset, width and height. In particular the driver must round +the vertical offset of the cropping rectangle to frame lines modulo +two, such that the field order cannot be confused.</para> + + <para>Second the driver adjusts the image size (the opposite +rectangle of the scaling process, source or target depending on the +data direction) to the closest size possible while maintaining the +current horizontal and vertical scaling factor.</para> + + <para>Finally the driver programs the hardware with the actual +cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a +write-only ioctl, it does not return the actual parameters. To query +them applications must call <constant>VIDIOC_G_CROP</constant> and +&VIDIOC-G-FMT;. When the parameters are unsuitable the application may +modify the cropping or image parameters and repeat the cycle until +satisfactory parameters have been negotiated.</para> + + <para>When cropping is not supported then no parameters are +changed and <constant>VIDIOC_S_CROP</constant> returns the +&EINVAL;.</para> + + <table pgwide="1" frame="none" id="v4l2-crop"> + <title>struct <structname>v4l2_crop</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>&v4l2-rect;</entry> + <entry><structfield>c</structfield></entry> + <entry>Cropping rectangle. The same co-ordinate system as +for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry> + </row> + </tbody> + </tgroup> + </table> + </refsect1> + + <refsect1> + &return-value; + </refsect1> +</refentry> |
