159 lines
4.8 KiB
XML
159 lines
4.8 KiB
XML
<refentry id="vidioc-enum-fmt">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_ENUM_FMT</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_ENUM_FMT</refname>
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<refpurpose>Enumerate image formats</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>struct v4l2_fmtdesc
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*<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>VIDIOC_ENUM_FMT</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>To enumerate image formats applications initialize the
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<structfield>type</structfield> and <structfield>index</structfield>
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field of &v4l2-fmtdesc; and call the
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<constant>VIDIOC_ENUM_FMT</constant> ioctl with a pointer to this
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structure. Drivers fill the rest of the structure or return an
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&EINVAL;. All formats are enumerable by beginning at index zero and
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incrementing by one until <errorcode>EINVAL</errorcode> is
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returned.</para>
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<table pgwide="1" frame="none" id="v4l2-fmtdesc">
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<title>struct <structname>v4l2_fmtdesc</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>index</structfield></entry>
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<entry>Number of the format in the enumeration, set by
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the application. This is in no way related to the <structfield>
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pixelformat</structfield> field.</entry>
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</row>
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<row>
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<entry>&v4l2-buf-type;</entry>
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<entry><structfield>type</structfield></entry>
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<entry>Type of the data stream, set by the application.
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Only these types are valid here:
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<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
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<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>,
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<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>,
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<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>,
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<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>, and custom (driver
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defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant>
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and higher.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>flags</structfield></entry>
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<entry>See <xref linkend="fmtdesc-flags" /></entry>
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</row>
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<row>
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<entry>__u8</entry>
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<entry><structfield>description</structfield>[32]</entry>
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<entry>Description of the format, a NUL-terminated ASCII
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string. This information is intended for the user, for example: "YUV
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4:2:2".</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>pixelformat</structfield></entry>
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<entry>The image format identifier. This is a
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four character code as computed by the v4l2_fourcc()
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macro:</entry>
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</row>
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<row>
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<entry spanname="hspan"><para><programlisting id="v4l2-fourcc">
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#define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))
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</programlisting></para><para>Several image formats are already
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defined by this specification in <xref linkend="pixfmt" />. Note these
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codes are not the same as those used in the Windows world.</para></entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>reserved</structfield>[4]</entry>
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<entry>Reserved for future extensions. Drivers must set
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the array to zero.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="fmtdesc-flags">
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<title>Image Format Description Flags</title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_FMT_FLAG_COMPRESSED</constant></entry>
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<entry>0x0001</entry>
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<entry>This is a compressed format.</entry>
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</row>
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<row>
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<entry><constant>V4L2_FMT_FLAG_EMULATED</constant></entry>
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<entry>0x0002</entry>
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<entry>This format is not native to the device but emulated
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through software (usually libv4l2), where possible try to use a native format
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instead for better performance.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>The &v4l2-fmtdesc; <structfield>type</structfield>
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is not supported or the <structfield>index</structfield> is out of
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bounds.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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