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Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-g-selection.xml')
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diff --git a/Documentation/DocBook/media/v4l/vidioc-g-selection.xml b/Documentation/DocBook/media/v4l/vidioc-g-selection.xml new file mode 100644 index 00000000..b11ec75e --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-g-selection.xml @@ -0,0 +1,241 @@ +<refentry id="vidioc-g-selection"> + + <refmeta> + <refentrytitle>ioctl VIDIOC_G_SELECTION, VIDIOC_S_SELECTION</refentrytitle> + &manvol; + </refmeta> + + <refnamediv> + <refname>VIDIOC_G_SELECTION</refname> + <refname>VIDIOC_S_SELECTION</refname> + <refpurpose>Get or set one of the selection rectangles</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_selection *<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_SELECTION, VIDIOC_S_SELECTION</para> + </listitem> + </varlistentry> + <varlistentry> + <term><parameter>argp</parameter></term> + <listitem> + <para></para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Description</title> + + <note> + <title>Experimental</title> + <para>This is an <link linkend="experimental"> experimental </link> + interface and may change in the future.</para> + </note> + + <para>The ioctls are used to query and configure selection rectangles.</para> + +<para> To query the cropping (composing) rectangle set &v4l2-selection; +<structfield> type </structfield> field to the respective buffer type. +Do not use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE +</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE +</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of +<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is +setting the value of &v4l2-selection; <structfield>target</structfield> field +to <constant> V4L2_SEL_TGT_CROP </constant> (<constant> +V4L2_SEL_TGT_COMPOSE </constant>). Please refer to table <xref +linkend="v4l2-selections-common" /> or <xref linkend="selection-api" /> for additional +targets. The <structfield>flags</structfield> and <structfield>reserved +</structfield> fields of &v4l2-selection; are ignored and they must be filled +with zeros. The driver fills the rest of the structure or +returns &EINVAL; if incorrect buffer type or target was used. If cropping +(composing) is not supported then the active rectangle is not mutable and it is +always equal to the bounds rectangle. Finally, the &v4l2-rect; +<structfield>r</structfield> rectangle is filled with the current cropping +(composing) coordinates. The coordinates are expressed in driver-dependent +units. The only exception are rectangles for images in raw formats, whose +coordinates are always expressed in pixels. </para> + +<para> To change the cropping (composing) rectangle set the &v4l2-selection; +<structfield>type</structfield> field to the respective buffer type. Do not +use multiplanar buffers. Use <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE +</constant> instead of <constant> V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE +</constant>. Use <constant> V4L2_BUF_TYPE_VIDEO_OUTPUT </constant> instead of +<constant> V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE </constant>. The next step is +setting the value of &v4l2-selection; <structfield>target</structfield> to +<constant>V4L2_SEL_TGT_CROP</constant> (<constant> +V4L2_SEL_TGT_COMPOSE </constant>). Please refer to table <xref +linkend="v4l2-selections-common" /> or <xref linkend="selection-api" /> for additional +targets. The &v4l2-rect; <structfield>r</structfield> rectangle need to be +set to the desired active area. Field &v4l2-selection; <structfield> reserved +</structfield> is ignored and must be filled with zeros. The driver may adjust +coordinates of the requested rectangle. An application may +introduce constraints to control rounding behaviour. The &v4l2-selection; +<structfield>flags</structfield> field must be set to one of the following: + +<itemizedlist> + <listitem> +<para><constant>0</constant> - The driver can adjust the rectangle size freely +and shall choose a crop/compose rectangle as close as possible to the requested +one.</para> + </listitem> + <listitem> +<para><constant>V4L2_SEL_FLAG_GE</constant> - The driver is not allowed to +shrink the rectangle. The original rectangle must lay inside the adjusted +one.</para> + </listitem> + <listitem> +<para><constant>V4L2_SEL_FLAG_LE</constant> - The driver is not allowed to +enlarge the rectangle. The adjusted rectangle must lay inside the original +one.</para> + </listitem> + <listitem> +<para><constant>V4L2_SEL_FLAG_GE | V4L2_SEL_FLAG_LE</constant> - The driver +must choose the size exactly the same as in the requested rectangle.</para> + </listitem> +</itemizedlist> + +Please refer to <xref linkend="sel-const-adjust" />. + +</para> + +<para> The driver may have to adjusts the requested dimensions against hardware +limits and other parts as the pipeline, i.e. the bounds given by the +capture/output window or TV display. The closest possible values of horizontal +and vertical offset and sizes are chosen according to following priority: + +<orderedlist> + <listitem> + <para>Satisfy constraints from &v4l2-selection; <structfield>flags</structfield>.</para> + </listitem> + <listitem> + <para>Adjust width, height, left, and top to hardware limits and alignments.</para> + </listitem> + <listitem> + <para>Keep center of adjusted rectangle as close as possible to the original one.</para> + </listitem> + <listitem> + <para>Keep width and height as close as possible to original ones.</para> + </listitem> + <listitem> + <para>Keep horizontal and vertical offset as close as possible to original ones.</para> + </listitem> +</orderedlist> + +On success the &v4l2-rect; <structfield>r</structfield> field contains +the adjusted rectangle. When the parameters are unsuitable the application may +modify the cropping (composing) or image parameters and repeat the cycle until +satisfactory parameters have been negotiated. If constraints flags have to be +violated at then ERANGE is returned. The error indicates that <emphasis> there +exist no rectangle </emphasis> that satisfies the constraints.</para> + + <para>Selection targets and flags are documented in <xref + linkend="v4l2-selections-common"/>.</para> + + <para> + <figure id="sel-const-adjust"> + <title>Size adjustments with constraint flags.</title> + <mediaobject> + <imageobject> + <imagedata fileref="constraints.png" format="PNG" /> + </imageobject> + <textobject> + <phrase>Behaviour of rectangle adjustment for different constraint + flags.</phrase> + </textobject> + </mediaobject> + </figure> + </para> + + <para> + <table pgwide="1" frame="none" id="v4l2-selection"> + <title>struct <structname>v4l2_selection</structname></title> + <tgroup cols="3"> + &cs-str; + <tbody valign="top"> + <row> + <entry>__u32</entry> + <entry><structfield>type</structfield></entry> + <entry>Type of the buffer (from &v4l2-buf-type;).</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>target</structfield></entry> + <entry>Used to select between <link linkend="v4l2-selections-common"> cropping + and composing rectangles</link>.</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>flags</structfield></entry> + <entry>Flags controlling the selection rectangle adjustments, refer to + <link linkend="v4l2-selection-flags">selection flags</link>.</entry> + </row> + <row> + <entry>&v4l2-rect;</entry> + <entry><structfield>r</structfield></entry> + <entry>The selection rectangle.</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>reserved[9]</structfield></entry> + <entry>Reserved fields for future use.</entry> + </row> + </tbody> + </tgroup> + </table> + </para> + </refsect1> + + <refsect1> + &return-value; + <variablelist> + <varlistentry> + <term><errorcode>EINVAL</errorcode></term> + <listitem> + <para>Given buffer type <structfield>type</structfield> or +the selection target <structfield>target</structfield> is not supported, +or the <structfield>flags</structfield> argument is not valid.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>ERANGE</errorcode></term> + <listitem> + <para>It is not possible to adjust &v4l2-rect; <structfield> +r</structfield> rectangle to satisfy all contraints given in the +<structfield>flags</structfield> argument.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>EBUSY</errorcode></term> + <listitem> + <para>It is not possible to apply change of the selection rectangle +at the moment. Usually because streaming is in progress.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + +</refentry> |