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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:02 EST.

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>These ioctls are <emphasis role="bold">deprecated</emphasis>.
61	    New drivers and applications should use <link linkend="jpeg-controls">
62	    JPEG class controls</link> for image quality and JPEG markers control.
63	    </para>
64	
65	    <para>[to do]</para>
66	
67	    <para>Ronald Bultje elaborates:</para>
68	
69	    <!-- See video4linux-list@redhat.com on 16 Oct 2002, subject
70	"Re: [V4L] Re: v4l2 api / Zoran v4l2_jpegcompression" -->
71	
72	    <para>APP is some application-specific information. The
73	application can set it itself, and it'll be stored in the JPEG-encoded
74	fields (eg; interlacing information for in an AVI or so). COM is the
75	same, but it's comments, like 'encoded by me' or so.</para>
76	
77	    <para>jpeg_markers describes whether the huffman tables,
78	quantization tables and the restart interval information (all
79	JPEG-specific stuff) should be stored in the JPEG-encoded fields.
80	These define how the JPEG field is encoded. If you omit them,
81	applications assume you've used standard encoding. You usually do want
82	to add them.</para>
83	
84	    <!-- NB VIDIOC_S_JPEGCOMP is w/o. -->
85	
86	    <table pgwide="1" frame="none" id="v4l2-jpegcompression">
87	      <title>struct <structname>v4l2_jpegcompression</structname></title>
88	      <tgroup cols="3">
89		&cs-str;
90		<tbody valign="top">
91		  <row>
92		    <entry>int</entry>
93		    <entry><structfield>quality</structfield></entry>
94		    <entry>Deprecated. If <link linkend="jpeg-quality-control"><constant>
95		    V4L2_CID_JPEG_COMPRESSION_QUALITY</constant></link> control is exposed
96		    by a driver applications should use it instead and ignore this field.
97		    </entry>
98		  </row>
99		  <row>
100		    <entry>int</entry>
101		    <entry><structfield>APPn</structfield></entry>
102		    <entry></entry>
103		  </row>
104		  <row>
105		    <entry>int</entry>
106		    <entry><structfield>APP_len</structfield></entry>
107		    <entry></entry>
108		  </row>
109		  <row>
110		    <entry>char</entry>
111		    <entry><structfield>APP_data</structfield>[60]</entry>
112		    <entry></entry>
113		  </row>
114		  <row>
115		    <entry>int</entry>
116		    <entry><structfield>COM_len</structfield></entry>
117		    <entry></entry>
118		  </row>
119		  <row>
120		    <entry>char</entry>
121		    <entry><structfield>COM_data</structfield>[60]</entry>
122		    <entry></entry>
123		  </row>
124		  <row>
125		    <entry>__u32</entry>
126		    <entry><structfield>jpeg_markers</structfield></entry>
127		    <entry>See <xref linkend="jpeg-markers"/>. Deprecated.
128		    If <link linkend="jpeg-active-marker-control"><constant>
129		    V4L2_CID_JPEG_ACTIVE_MARKER</constant></link> control
130		    is exposed by a driver applications should use it instead
131		    and ignore this field.</entry>
132		  </row>
133		</tbody>
134	      </tgroup>
135	    </table>
136	
137	    <table pgwide="1" frame="none" id="jpeg-markers">
138	      <title>JPEG Markers Flags</title>
139	      <tgroup cols="3">
140		&cs-def;
141		<tbody valign="top">
142		  <row>
143		    <entry><constant>V4L2_JPEG_MARKER_DHT</constant></entry>
144		    <entry>(1&lt;&lt;3)</entry>
145		    <entry>Define Huffman Tables</entry>
146		  </row>
147		  <row>
148		    <entry><constant>V4L2_JPEG_MARKER_DQT</constant></entry>
149		    <entry>(1&lt;&lt;4)</entry>
150		    <entry>Define Quantization Tables</entry>
151		  </row>
152		  <row>
153		    <entry><constant>V4L2_JPEG_MARKER_DRI</constant></entry>
154		    <entry>(1&lt;&lt;5)</entry>
155		    <entry>Define Restart Interval</entry>
156		  </row>
157		  <row>
158		    <entry><constant>V4L2_JPEG_MARKER_COM</constant></entry>
159		    <entry>(1&lt;&lt;6)</entry>
160		    <entry>Comment segment</entry>
161		  </row>
162		  <row>
163		    <entry><constant>V4L2_JPEG_MARKER_APP</constant></entry>
164		    <entry>(1&lt;&lt;7)</entry>
165		    <entry>App segment, driver will always use APP0</entry>
166		  </row>
167		</tbody>
168	      </tgroup>
169	    </table>
170	  </refsect1>
171	
172	  <refsect1>
173	    &return-value;
174	  </refsect1>
175	</refentry>
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