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>
54field of &v4l2-fmtdesc; and call the
55<constant>VIDIOC_ENUM_FMT</constant> ioctl with a pointer to this
56structure. Drivers fill the rest of the structure or return an
57&EINVAL;. All formats are enumerable by beginning at index zero and
58incrementing by one until <errorcode>EINVAL</errorcode> is
59returned.</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
70the application. This is in no way related to the <structfield>
71pixelformat</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.
77Only 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
83defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant>
84and 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
95string. This information is intended for the user, for example: "YUV
964:2:2".</entry>
97	  </row>
98	  <row>
99	    <entry>__u32</entry>
100	    <entry><structfield>pixelformat</structfield></entry>
101	    <entry>The image format identifier. This is a
102four character code as computed by the v4l2_fourcc()
103macro:</entry>
104	  </row>
105	  <row>
106	    <entry spanname="hspan"><para><programlisting id="v4l2-fourcc">
107#define v4l2_fourcc(a,b,c,d) (((__u32)(a)&lt;&lt;0)|((__u32)(b)&lt;&lt;8)|((__u32)(c)&lt;&lt;16)|((__u32)(d)&lt;&lt;24))
108</programlisting></para><para>Several image formats are already
109defined by this specification in <xref linkend="pixfmt" />. Note these
110codes 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
116the 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
136through software (usually libv4l2), where possible try to use a native format
137instead 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>
152is not supported or the <structfield>index</structfield> is out of
153bounds.</para>
154	</listitem>
155      </varlistentry>
156    </variablelist>
157  </refsect1>
158</refentry>
159