Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <refentry id="vidioc-enum-fmt"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_ENUM_FMT</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_ENUM_FMT</refname> 9 <refpurpose>Enumerate image formats</refpurpose> 10 </refnamediv> 11 12 <refsynopsisdiv> 13 <funcsynopsis> 14 <funcprototype> 15 <funcdef>int <function>ioctl</function></funcdef> 16 <paramdef>int <parameter>fd</parameter></paramdef> 17 <paramdef>int <parameter>request</parameter></paramdef> 18 <paramdef>struct v4l2_fmtdesc 19 *<parameter>argp</parameter></paramdef> 20 </funcprototype> 21 </funcsynopsis> 22 </refsynopsisdiv> 23 24 <refsect1> 25 <title>Arguments</title> 26 27 <variablelist> 28 <varlistentry> 29 <term><parameter>fd</parameter></term> 30 <listitem> 31 <para>&fd;</para> 32 </listitem> 33 </varlistentry> 34 <varlistentry> 35 <term><parameter>request</parameter></term> 36 <listitem> 37 <para>VIDIOC_ENUM_FMT</para> 38 </listitem> 39 </varlistentry> 40 <varlistentry> 41 <term><parameter>argp</parameter></term> 42 <listitem> 43 <para></para> 44 </listitem> 45 </varlistentry> 46 </variablelist> 47 </refsect1> 48 49 <refsect1> 50 <title>Description</title> 51 52 <para>To enumerate image formats applications initialize the 53 <structfield>type</structfield> and <structfield>index</structfield> 54 field of &v4l2-fmtdesc; and call the 55 <constant>VIDIOC_ENUM_FMT</constant> ioctl with a pointer to this 56 structure. Drivers fill the rest of the structure or return an 57 &EINVAL;. All formats are enumerable by beginning at index zero and 58 incrementing by one until <errorcode>EINVAL</errorcode> is 59 returned.</para> 60 61 <table pgwide="1" frame="none" id="v4l2-fmtdesc"> 62 <title>struct <structname>v4l2_fmtdesc</structname></title> 63 <tgroup cols="3"> 64 &cs-str; 65 <tbody valign="top"> 66 <row> 67 <entry>__u32</entry> 68 <entry><structfield>index</structfield></entry> 69 <entry>Number of the format in the enumeration, set by 70 the application. This is in no way related to the <structfield> 71 pixelformat</structfield> field.</entry> 72 </row> 73 <row> 74 <entry>&v4l2-buf-type;</entry> 75 <entry><structfield>type</structfield></entry> 76 <entry>Type of the data stream, set by the application. 77 Only these types are valid here: 78 <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>, 79 <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>, 80 <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>, 81 <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>, 82 <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>, and custom (driver 83 defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant> 84 and higher.</entry> 85 </row> 86 <row> 87 <entry>__u32</entry> 88 <entry><structfield>flags</structfield></entry> 89 <entry>See <xref linkend="fmtdesc-flags" /></entry> 90 </row> 91 <row> 92 <entry>__u8</entry> 93 <entry><structfield>description</structfield>[32]</entry> 94 <entry>Description of the format, a NUL-terminated ASCII 95 string. This information is intended for the user, for example: "YUV 96 4:2:2".</entry> 97 </row> 98 <row> 99 <entry>__u32</entry> 100 <entry><structfield>pixelformat</structfield></entry> 101 <entry>The image format identifier. This is a 102 four character code as computed by the v4l2_fourcc() 103 macro:</entry> 104 </row> 105 <row> 106 <entry spanname="hspan"><para><programlisting id="v4l2-fourcc"> 107 #define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24)) 108 </programlisting></para><para>Several image formats are already 109 defined by this specification in <xref linkend="pixfmt" />. Note these 110 codes are not the same as those used in the Windows world.</para></entry> 111 </row> 112 <row> 113 <entry>__u32</entry> 114 <entry><structfield>reserved</structfield>[4]</entry> 115 <entry>Reserved for future extensions. Drivers must set 116 the array to zero.</entry> 117 </row> 118 </tbody> 119 </tgroup> 120 </table> 121 122 <table pgwide="1" frame="none" id="fmtdesc-flags"> 123 <title>Image Format Description Flags</title> 124 <tgroup cols="3"> 125 &cs-def; 126 <tbody valign="top"> 127 <row> 128 <entry><constant>V4L2_FMT_FLAG_COMPRESSED</constant></entry> 129 <entry>0x0001</entry> 130 <entry>This is a compressed format.</entry> 131 </row> 132 <row> 133 <entry><constant>V4L2_FMT_FLAG_EMULATED</constant></entry> 134 <entry>0x0002</entry> 135 <entry>This format is not native to the device but emulated 136 through software (usually libv4l2), where possible try to use a native format 137 instead for better performance.</entry> 138 </row> 139 </tbody> 140 </tgroup> 141 </table> 142 </refsect1> 143 144 <refsect1> 145 &return-value; 146 147 <variablelist> 148 <varlistentry> 149 <term><errorcode>EINVAL</errorcode></term> 150 <listitem> 151 <para>The &v4l2-fmtdesc; <structfield>type</structfield> 152 is not supported or the <structfield>index</structfield> is out of 153 bounds.</para> 154 </listitem> 155 </varlistentry> 156 </variablelist> 157 </refsect1> 158 </refentry> 159 160 <!-- 161 Local Variables: 162 mode: sgml 163 sgml-parent-document: "v4l2.sgml" 164 indent-tabs-mode: nil 165 End: 166 -->
