About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / DocBook / v4l / vidioc-g-jpegcomp.xml


Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 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>[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
68	application can set it itself, and it'll be stored in the JPEG-encoded
69	fields (eg; interlacing information for in an AVI or so). COM is the
70	same, but it's comments, like 'encoded by me' or so.</para>
71	
72	    <para>jpeg_markers describes whether the huffman tables,
73	quantization tables and the restart interval information (all
74	JPEG-specific stuff) should be stored in the JPEG-encoded fields.
75	These define how the JPEG field is encoded. If you omit them,
76	applications assume you've used standard encoding. You usually do want
77	to 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	<!--
175	Local Variables:
176	mode: sgml
177	sgml-parent-document: "v4l2.sgml"
178	indent-tabs-mode: nil
179	End:
180	-->
Hide Line Numbers


About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog