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<refentry id="vidioc-enum-fmt">
<refmeta>
<refentrytitle>ioctl VIDIOC_ENUM_FMT</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_ENUM_FMT</refname>
<refpurpose>Enumerate image formats</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_fmtdesc
*<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_FMT</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>To enumerate image formats applications initialize the
<structfield>type</structfield> and <structfield>index</structfield>
field of &v4l2-fmtdesc; and call the
<constant>VIDIOC_ENUM_FMT</constant> ioctl with a pointer to this
structure. Drivers fill the rest of the structure or return an
&EINVAL;. All formats are enumerable by beginning at index zero and
incrementing by one until <errorcode>EINVAL</errorcode> is
returned.</para>
<para>Note that after switching input or output the list of enumerated image
formats may be different.</para>
<table pgwide="1" frame="none" id="v4l2-fmtdesc">
<title>struct <structname>v4l2_fmtdesc</structname></title>
<tgroup cols="3">
&cs-str;
<tbody valign="top">
<row>
<entry>__u32</entry>
<entry><structfield>index</structfield></entry>
<entry>Number of the format in the enumeration, set by
the application. This is in no way related to the <structfield>
pixelformat</structfield> field.</entry>
</row>
<row>
<entry>__u32</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_CAPTURE_MPLANE</constant>,
<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>,
<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant> and
<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>flags</structfield></entry>
<entry>See <xref linkend="fmtdesc-flags" /></entry>
</row>
<row>
<entry>__u8</entry>
<entry><structfield>description</structfield>[32]</entry>
<entry>Description of the format, a NUL-terminated ASCII
string. This information is intended for the user, for example: "YUV
4:2:2".</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>pixelformat</structfield></entry>
<entry>The image format identifier. This is a
four character code as computed by the v4l2_fourcc()
macro:</entry>
</row>
<row>
<entry spanname="hspan"><para><programlisting id="v4l2-fourcc">
#define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))
</programlisting></para><para>Several image formats are already
defined by this specification in <xref linkend="pixfmt" />. Note these
codes are not the same as those used in the Windows world.</para></entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[4]</entry>
<entry>Reserved for future extensions. Drivers must set
the array to zero.</entry>
</row>
</tbody>
</tgroup>
</table>
<table pgwide="1" frame="none" id="fmtdesc-flags">
<title>Image Format Description Flags</title>
<tgroup cols="3">
&cs-def;
<tbody valign="top">
<row>
<entry><constant>V4L2_FMT_FLAG_COMPRESSED</constant></entry>
<entry>0x0001</entry>
<entry>This is a compressed format.</entry>
</row>
<row>
<entry><constant>V4L2_FMT_FLAG_EMULATED</constant></entry>
<entry>0x0002</entry>
<entry>This format is not native to the device but emulated
through software (usually libv4l2), where possible try to use a native format
instead for better performance.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
&return-value;
<variablelist>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The &v4l2-fmtdesc; <structfield>type</structfield>
is not supported or the <structfield>index</structfield> is out of
bounds.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
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