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1<refentry id="vidioc-g-jpegcomp">
2 <refmeta>
3 <refentrytitle>ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</refentrytitle>
4 &manvol;
5 </refmeta>
6
7 <refnamediv>
8 <refname>VIDIOC_G_JPEGCOMP</refname>
9 <refname>VIDIOC_S_JPEGCOMP</refname>
10 <refpurpose></refpurpose>
11 </refnamediv>
12
13 <refsynopsisdiv>
14 <funcsynopsis>
15 <funcprototype>
16 <funcdef>int <function>ioctl</function></funcdef>
17 <paramdef>int <parameter>fd</parameter></paramdef>
18 <paramdef>int <parameter>request</parameter></paramdef>
19 <paramdef>v4l2_jpegcompression *<parameter>argp</parameter></paramdef>
20 </funcprototype>
21 </funcsynopsis>
22 <funcsynopsis>
23 <funcprototype>
24 <funcdef>int <function>ioctl</function></funcdef>
25 <paramdef>int <parameter>fd</parameter></paramdef>
26 <paramdef>int <parameter>request</parameter></paramdef>
27 <paramdef>const v4l2_jpegcompression *<parameter>argp</parameter></paramdef>
28 </funcprototype>
29 </funcsynopsis>
30 </refsynopsisdiv>
31
32 <refsect1>
33 <title>Arguments</title>
34
35 <variablelist>
36 <varlistentry>
37 <term><parameter>fd</parameter></term>
38 <listitem>
39 <para>&fd;</para>
40 </listitem>
41 </varlistentry>
42 <varlistentry>
43 <term><parameter>request</parameter></term>
44 <listitem>
45 <para>VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</para>
46 </listitem>
47 </varlistentry>
48 <varlistentry>
49 <term><parameter>argp</parameter></term>
50 <listitem>
51 <para></para>
52 </listitem>
53 </varlistentry>
54 </variablelist>
55 </refsect1>
56
57 <refsect1>
58 <title>Description</title>
59
60 <para>[to do]</para>
61
62 <para>Ronald Bultje elaborates:</para>
63
64 <!-- See video4linux-list@redhat.com on 16 Oct 2002, subject
65"Re: [V4L] Re: v4l2 api / Zoran v4l2_jpegcompression" -->
66
67 <para>APP is some application-specific information. The
68application can set it itself, and it'll be stored in the JPEG-encoded
69fields (eg; interlacing information for in an AVI or so). COM is the
70same, but it's comments, like 'encoded by me' or so.</para>
71
72 <para>jpeg_markers describes whether the huffman tables,
73quantization tables and the restart interval information (all
74JPEG-specific stuff) should be stored in the JPEG-encoded fields.
75These define how the JPEG field is encoded. If you omit them,
76applications assume you've used standard encoding. You usually do want
77to add them.</para>
78
79 <!-- NB VIDIOC_S_JPEGCOMP is w/o. -->
80
81 <table pgwide="1" frame="none" id="v4l2-jpegcompression">
82 <title>struct <structname>v4l2_jpegcompression</structname></title>
83 <tgroup cols="3">
84 &cs-str;
85 <tbody valign="top">
86 <row>
87 <entry>int</entry>
88 <entry><structfield>quality</structfield></entry>
89 <entry></entry>
90 </row>
91 <row>
92 <entry>int</entry>
93 <entry><structfield>APPn</structfield></entry>
94 <entry></entry>
95 </row>
96 <row>
97 <entry>int</entry>
98 <entry><structfield>APP_len</structfield></entry>
99 <entry></entry>
100 </row>
101 <row>
102 <entry>char</entry>
103 <entry><structfield>APP_data</structfield>[60]</entry>
104 <entry></entry>
105 </row>
106 <row>
107 <entry>int</entry>
108 <entry><structfield>COM_len</structfield></entry>
109 <entry></entry>
110 </row>
111 <row>
112 <entry>char</entry>
113 <entry><structfield>COM_data</structfield>[60]</entry>
114 <entry></entry>
115 </row>
116 <row>
117 <entry>__u32</entry>
118 <entry><structfield>jpeg_markers</structfield></entry>
119 <entry>See <xref linkend="jpeg-markers" />.</entry>
120 </row>
121 </tbody>
122 </tgroup>
123 </table>
124
125 <table pgwide="1" frame="none" id="jpeg-markers">
126 <title>JPEG Markers Flags</title>
127 <tgroup cols="3">
128 &cs-def;
129 <tbody valign="top">
130 <row>
131 <entry><constant>V4L2_JPEG_MARKER_DHT</constant></entry>
132 <entry>(1&lt;&lt;3)</entry>
133 <entry>Define Huffman Tables</entry>
134 </row>
135 <row>
136 <entry><constant>V4L2_JPEG_MARKER_DQT</constant></entry>
137 <entry>(1&lt;&lt;4)</entry>
138 <entry>Define Quantization Tables</entry>
139 </row>
140 <row>
141 <entry><constant>V4L2_JPEG_MARKER_DRI</constant></entry>
142 <entry>(1&lt;&lt;5)</entry>
143 <entry>Define Restart Interval</entry>
144 </row>
145 <row>
146 <entry><constant>V4L2_JPEG_MARKER_COM</constant></entry>
147 <entry>(1&lt;&lt;6)</entry>
148 <entry>Comment segment</entry>
149 </row>
150 <row>
151 <entry><constant>V4L2_JPEG_MARKER_APP</constant></entry>
152 <entry>(1&lt;&lt;7)</entry>
153 <entry>App segment, driver will always use APP0</entry>
154 </row>
155 </tbody>
156 </tgroup>
157 </table>
158 </refsect1>
159
160 <refsect1>
161 &return-value;
162
163 <variablelist>
164 <varlistentry>
165 <term><errorcode>EINVAL</errorcode></term>
166 <listitem>
167 <para>This ioctl is not supported.</para>
168 </listitem>
169 </varlistentry>
170 </variablelist>
171 </refsect1>
172</refentry>
173
174<!--
175Local Variables:
176mode: sgml
177sgml-parent-document: "v4l2.sgml"
178indent-tabs-mode: nil
179End:
180-->
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