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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>, | |
53b5d574 | 79 | <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE</constant>, |
8e080c2e | 80 | <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>, |
53b5d574 | 81 | <constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE</constant>, |
8e080c2e MCC |
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> |