+++ /dev/null
-<refentry id="vidioc-enum-frameintervals">
-
- <refmeta>
- <refentrytitle>ioctl VIDIOC_ENUM_FRAMEINTERVALS</refentrytitle>
- &manvol;
- </refmeta>
-
- <refnamediv>
- <refname>VIDIOC_ENUM_FRAMEINTERVALS</refname>
- <refpurpose>Enumerate frame intervals</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_frmivalenum *<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_ENUM_FRAMEINTERVALS</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>argp</parameter></term>
- <listitem>
- <para>Pointer to a &v4l2-frmivalenum; structure that
-contains a pixel format and size and receives a frame interval.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>Description</title>
-
- <para>This ioctl allows applications to enumerate all frame
-intervals that the device supports for the given pixel format and
-frame size.</para>
- <para>The supported pixel formats and frame sizes can be obtained
-by using the &VIDIOC-ENUM-FMT; and &VIDIOC-ENUM-FRAMESIZES;
-functions.</para>
- <para>The return value and the content of the
-<structfield>v4l2_frmivalenum.type</structfield> field depend on the
-type of frame intervals the device supports. Here are the semantics of
-the function for the different cases:</para>
- <itemizedlist>
- <listitem>
- <para><emphasis role="bold">Discrete:</emphasis> The function
-returns success if the given index value (zero-based) is valid. The
-application should increase the index by one for each call until
-<constant>EINVAL</constant> is returned. The `v4l2_frmivalenum.type`
-field is set to `V4L2_FRMIVAL_TYPE_DISCRETE` by the driver. Of the
-union only the `discrete` member is valid.</para>
- </listitem>
- <listitem>
- <para><emphasis role="bold">Step-wise:</emphasis> The function
-returns success if the given index value is zero and
-<constant>EINVAL</constant> for any other index value. The
-<structfield>v4l2_frmivalenum.type</structfield> field is set to
-<constant>V4L2_FRMIVAL_TYPE_STEPWISE</constant> by the driver. Of the
-union only the <structfield>stepwise</structfield> member is
-valid.</para>
- </listitem>
- <listitem>
- <para><emphasis role="bold">Continuous:</emphasis> This is a
-special case of the step-wise type above. The function returns success
-if the given index value is zero and <constant>EINVAL</constant> for
-any other index value. The
-<structfield>v4l2_frmivalenum.type</structfield> field is set to
-<constant>V4L2_FRMIVAL_TYPE_CONTINUOUS</constant> by the driver. Of
-the union only the <structfield>stepwise</structfield> member is valid
-and the <structfield>step</structfield> value is set to 1.</para>
- </listitem>
- </itemizedlist>
-
- <para>When the application calls the function with index zero, it
-must check the <structfield>type</structfield> field to determine the
-type of frame interval enumeration the device supports. Only for the
-<constant>V4L2_FRMIVAL_TYPE_DISCRETE</constant> type does it make
-sense to increase the index value to receive more frame
-intervals.</para>
- <para>Note that the order in which the frame intervals are
-returned has no special meaning. In particular does it not say
-anything about potential default frame intervals.</para>
- <para>Applications can assume that the enumeration data does not
-change without any interaction from the application itself. This means
-that the enumeration data is consistent if the application does not
-perform any other ioctl calls while it runs the frame interval
-enumeration.</para>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <itemizedlist>
- <listitem>
- <para><emphasis role="bold">Frame intervals and frame
-rates:</emphasis> The V4L2 API uses frame intervals instead of frame
-rates. Given the frame interval the frame rate can be computed as
-follows:<screen>frame_rate = 1 / frame_interval</screen></para>
- </listitem>
- </itemizedlist>
-
- </refsect1>
-
- <refsect1>
- <title>Structs</title>
-
- <para>In the structs below, <emphasis>IN</emphasis> denotes a
-value that has to be filled in by the application,
-<emphasis>OUT</emphasis> denotes values that the driver fills in. The
-application should zero out all members except for the
-<emphasis>IN</emphasis> fields.</para>
-
- <table pgwide="1" frame="none" id="v4l2-frmival-stepwise">
- <title>struct <structname>v4l2_frmival_stepwise</structname></title>
- <tgroup cols="3">
- &cs-str;
- <tbody valign="top">
- <row>
- <entry>&v4l2-fract;</entry>
- <entry><structfield>min</structfield></entry>
- <entry>Minimum frame interval [s].</entry>
- </row>
- <row>
- <entry>&v4l2-fract;</entry>
- <entry><structfield>max</structfield></entry>
- <entry>Maximum frame interval [s].</entry>
- </row>
- <row>
- <entry>&v4l2-fract;</entry>
- <entry><structfield>step</structfield></entry>
- <entry>Frame interval step size [s].</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
- <table pgwide="1" frame="none" id="v4l2-frmivalenum">
- <title>struct <structname>v4l2_frmivalenum</structname></title>
- <tgroup cols="4">
- <colspec colname="c1" />
- <colspec colname="c2" />
- <colspec colname="c3" />
- <colspec colname="c4" />
- <tbody valign="top">
- <row>
- <entry>__u32</entry>
- <entry><structfield>index</structfield></entry>
- <entry></entry>
- <entry>IN: Index of the given frame interval in the
-enumeration.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>pixel_format</structfield></entry>
- <entry></entry>
- <entry>IN: Pixel format for which the frame intervals are
-enumerated.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>width</structfield></entry>
- <entry></entry>
- <entry>IN: Frame width for which the frame intervals are
-enumerated.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>height</structfield></entry>
- <entry></entry>
- <entry>IN: Frame height for which the frame intervals are
-enumerated.</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>type</structfield></entry>
- <entry></entry>
- <entry>OUT: Frame interval type the device supports.</entry>
- </row>
- <row>
- <entry>union</entry>
- <entry></entry>
- <entry></entry>
- <entry>OUT: Frame interval with the given index.</entry>
- </row>
- <row>
- <entry></entry>
- <entry>&v4l2-fract;</entry>
- <entry><structfield>discrete</structfield></entry>
- <entry>Frame interval [s].</entry>
- </row>
- <row>
- <entry></entry>
- <entry>&v4l2-frmival-stepwise;</entry>
- <entry><structfield>stepwise</structfield></entry>
- <entry></entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>reserved[2]</structfield></entry>
- <entry></entry>
- <entry>Reserved space for future use.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
-
- <refsect1>
- <title>Enums</title>
-
- <table pgwide="1" frame="none" id="v4l2-frmivaltypes">
- <title>enum <structname>v4l2_frmivaltypes</structname></title>
- <tgroup cols="3">
- &cs-def;
- <tbody valign="top">
- <row>
- <entry><constant>V4L2_FRMIVAL_TYPE_DISCRETE</constant></entry>
- <entry>1</entry>
- <entry>Discrete frame interval.</entry>
- </row>
- <row>
- <entry><constant>V4L2_FRMIVAL_TYPE_CONTINUOUS</constant></entry>
- <entry>2</entry>
- <entry>Continuous frame interval.</entry>
- </row>
- <row>
- <entry><constant>V4L2_FRMIVAL_TYPE_STEPWISE</constant></entry>
- <entry>3</entry>
- <entry>Step-wise defined frame interval.</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </refsect1>
-
- <refsect1>
- &return-value;
-
- <para>See the description section above for a list of return
-values that <varname>errno</varname> can have.</para>
- </refsect1>
-
-</refentry>
-
-<!--
-Local Variables:
-mode: sgml
-sgml-parent-document: "v4l2.sgml"
-indent-tabs-mode: nil
-End:
--->
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