271 lines
8.3 KiB
XML
271 lines
8.3 KiB
XML
|
<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:
|
||
|
|
-->
|