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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:02 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	    <para>Note that after switching input or output the list of enumerated image
62	formats may be different.</para>
63	
64	    <table pgwide="1" frame="none" id="v4l2-fmtdesc">
65	      <title>struct <structname>v4l2_fmtdesc</structname></title>
66	      <tgroup cols="3">
67		&cs-str;
68		<tbody valign="top">
69		  <row>
70		    <entry>__u32</entry>
71		    <entry><structfield>index</structfield></entry>
72		    <entry>Number of the format in the enumeration, set by
73	the application. This is in no way related to the <structfield>
74	pixelformat</structfield> field.</entry>
75		  </row>
76		  <row>
77		    <entry>__u32</entry>
78		    <entry><structfield>type</structfield></entry>
79		    <entry>Type of the data stream, set by the application.
80	Only these types are valid here:
81	<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
82	<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>,
83	<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>,
84	<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant> and
85	<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>. See <xref linkend="v4l2-buf-type" />.</entry>
86		  </row>
87		  <row>
88		    <entry>__u32</entry>
89		    <entry><structfield>flags</structfield></entry>
90		    <entry>See <xref linkend="fmtdesc-flags" /></entry>
91		  </row>
92		  <row>
93		    <entry>__u8</entry>
94		    <entry><structfield>description</structfield>[32]</entry>
95		    <entry>Description of the format, a NUL-terminated ASCII
96	string. This information is intended for the user, for example: "YUV
97	4:2:2".</entry>
98		  </row>
99		  <row>
100		    <entry>__u32</entry>
101		    <entry><structfield>pixelformat</structfield></entry>
102		    <entry>The image format identifier. This is a
103	four character code as computed by the v4l2_fourcc()
104	macro:</entry>
105		  </row>
106		  <row>
107		    <entry spanname="hspan"><para><programlisting id="v4l2-fourcc">
108	#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))
109	</programlisting></para><para>Several image formats are already
110	defined by this specification in <xref linkend="pixfmt" />. Note these
111	codes are not the same as those used in the Windows world.</para></entry>
112		  </row>
113		  <row>
114		    <entry>__u32</entry>
115		    <entry><structfield>reserved</structfield>[4]</entry>
116		    <entry>Reserved for future extensions. Drivers must set
117	the array to zero.</entry>
118		  </row>
119		</tbody>
120	      </tgroup>
121	    </table>
122	
123	    <table pgwide="1" frame="none" id="fmtdesc-flags">
124	      <title>Image Format Description Flags</title>
125	      <tgroup cols="3">
126		&cs-def;
127		<tbody valign="top">
128		  <row>
129		    <entry><constant>V4L2_FMT_FLAG_COMPRESSED</constant></entry>
130		    <entry>0x0001</entry>
131		    <entry>This is a compressed format.</entry>
132		  </row>
133		  <row>
134		    <entry><constant>V4L2_FMT_FLAG_EMULATED</constant></entry>
135		    <entry>0x0002</entry>
136		    <entry>This format is not native to the device but emulated
137	through software (usually libv4l2), where possible try to use a native format
138	instead for better performance.</entry>
139		  </row>
140		</tbody>
141	      </tgroup>
142	    </table>
143	  </refsect1>
144	
145	  <refsect1>
146	    &return-value;
147	
148	    <variablelist>
149	      <varlistentry>
150		<term><errorcode>EINVAL</errorcode></term>
151		<listitem>
152		  <para>The &v4l2-fmtdesc; <structfield>type</structfield>
153	is not supported or the <structfield>index</structfield> is out of
154	bounds.</para>
155		</listitem>
156	      </varlistentry>
157	    </variablelist>
158	  </refsect1>
159	</refentry>
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