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authorMauro Carvalho Chehab <mchehab@redhat.com>2011-05-31 15:27:44 -0400
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-07-27 16:52:05 -0400
commit4266129964b8238526936d723de65b419d8069c6 (patch)
tree38c6b5cd3dc99b8599391ffad3b87e399bef56a2 /Documentation/DocBook/media/v4l/vidioc-g-crop.xml
parent04893043ae9ea8aa82b712491ed25ba6c4ffbca3 (diff)
[media] DocBook: Move all media docbook stuff into its own directory
This patch addresses several issues pointed by Randy Dunlap <rdunlap@xenotime.net> at changeset ece722c: - In the generated index.html file, "media" is listed first, but it should be listed in alphabetical order, not first. - The generated files are (hidden) in .tmpmedia/ - The link from the top-level index.html file to "media" is to media/index.html, but the file is actually in .tmpmedia/media/index.html - Please build docs with and without using "O=builddir" and test that. - Would it be possible for media to have its own Makefile instead of merging into this one? Due to the way cleandocs target works, I had to rename the media DocBook to media_api, otherwise cleandocs would remove the /media directory. Thanks-to: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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1<refentry id="vidioc-g-crop">
2 <refmeta>
3 <refentrytitle>ioctl VIDIOC_G_CROP, VIDIOC_S_CROP</refentrytitle>
4 &manvol;
5 </refmeta>
6
7 <refnamediv>
8 <refname>VIDIOC_G_CROP</refname>
9 <refname>VIDIOC_S_CROP</refname>
10 <refpurpose>Get or set the current cropping rectangle</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>struct v4l2_crop *<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 struct v4l2_crop *<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_CROP, VIDIOC_S_CROP</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 query the cropping rectangle size and position
61applications set the <structfield>type</structfield> field of a
62<structname>v4l2_crop</structname> structure to the respective buffer
63(stream) type and call the <constant>VIDIOC_G_CROP</constant> ioctl
64with a pointer to this structure. The driver fills the rest of the
65structure or returns the &EINVAL; if cropping is not supported.</para>
66
67 <para>To change the cropping rectangle applications initialize the
68<structfield>type</structfield> and &v4l2-rect; substructure named
69<structfield>c</structfield> of a v4l2_crop structure and call the
70<constant>VIDIOC_S_CROP</constant> ioctl with a pointer to this
71structure.</para>
72
73 <para>The driver first adjusts the requested dimensions against
74hardware limits, &ie; the bounds given by the capture/output window,
75and it rounds to the closest possible values of horizontal and
76vertical offset, width and height. In particular the driver must round
77the vertical offset of the cropping rectangle to frame lines modulo
78two, such that the field order cannot be confused.</para>
79
80 <para>Second the driver adjusts the image size (the opposite
81rectangle of the scaling process, source or target depending on the
82data direction) to the closest size possible while maintaining the
83current horizontal and vertical scaling factor.</para>
84
85 <para>Finally the driver programs the hardware with the actual
86cropping and image parameters. <constant>VIDIOC_S_CROP</constant> is a
87write-only ioctl, it does not return the actual parameters. To query
88them applications must call <constant>VIDIOC_G_CROP</constant> and
89&VIDIOC-G-FMT;. When the parameters are unsuitable the application may
90modify the cropping or image parameters and repeat the cycle until
91satisfactory parameters have been negotiated.</para>
92
93 <para>When cropping is not supported then no parameters are
94changed and <constant>VIDIOC_S_CROP</constant> returns the
95&EINVAL;.</para>
96
97 <table pgwide="1" frame="none" id="v4l2-crop">
98 <title>struct <structname>v4l2_crop</structname></title>
99 <tgroup cols="3">
100 &cs-str;
101 <tbody valign="top">
102 <row>
103 <entry>&v4l2-buf-type;</entry>
104 <entry><structfield>type</structfield></entry>
105 <entry>Type of the data stream, set by the application.
106Only these types are valid here: <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>,
107<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>,
108<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>, and custom (driver
109defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant>
110and higher.</entry>
111 </row>
112 <row>
113 <entry>&v4l2-rect;</entry>
114 <entry><structfield>c</structfield></entry>
115 <entry>Cropping rectangle. The same co-ordinate system as
116for &v4l2-cropcap; <structfield>bounds</structfield> is used.</entry>
117 </row>
118 </tbody>
119 </tgroup>
120 </table>
121 </refsect1>
122
123 <refsect1>
124 &return-value;
125
126 <variablelist>
127 <varlistentry>
128 <term><errorcode>EINVAL</errorcode></term>
129 <listitem>
130 <para>Cropping is not supported.</para>
131 </listitem>
132 </varlistentry>
133 </variablelist>
134 </refsect1>
135</refentry>
136
137<!--
138Local Variables:
139mode: sgml
140sgml-parent-document: "v4l2.sgml"
141indent-tabs-mode: nil
142End:
143-->