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1<refentry id="vidioc-encoder-cmd">
2 <refmeta>
3 <refentrytitle>ioctl VIDIOC_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD</refentrytitle>
4 &manvol;
5 </refmeta>
6
7 <refnamediv>
8 <refname>VIDIOC_ENCODER_CMD</refname>
9 <refname>VIDIOC_TRY_ENCODER_CMD</refname>
10 <refpurpose>Execute an encoder command</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_encoder_cmd *<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_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD</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 <note>
53 <title>Experimental</title>
54
55 <para>This is an <link linkend="experimental">experimental</link>
56interface and may change in the future.</para>
57 </note>
58
59 <para>These ioctls control an audio/video (usually MPEG-) encoder.
60<constant>VIDIOC_ENCODER_CMD</constant> sends a command to the
61encoder, <constant>VIDIOC_TRY_ENCODER_CMD</constant> can be used to
62try a command without actually executing it.</para>
63
64 <para>To send a command applications must initialize all fields of a
65 &v4l2-encoder-cmd; and call
66 <constant>VIDIOC_ENCODER_CMD</constant> or
67 <constant>VIDIOC_TRY_ENCODER_CMD</constant> with a pointer to this
68 structure.</para>
69
70 <para>The <structfield>cmd</structfield> field must contain the
71command code. The <structfield>flags</structfield> field is currently
72only used by the STOP command and contains one bit: If the
73<constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant> flag is set,
74encoding will continue until the end of the current <wordasword>Group
75Of Pictures</wordasword>, otherwise it will stop immediately.</para>
76
77 <para>A <function>read</function>() call sends a START command to
78the encoder if it has not been started yet. After a STOP command,
79<function>read</function>() calls will read the remaining data
80buffered by the driver. When the buffer is empty,
81<function>read</function>() will return zero and the next
82<function>read</function>() call will restart the encoder.</para>
83
84 <para>A <function>close</function>() call sends an immediate STOP
85to the encoder, and all buffered data is discarded.</para>
86
87 <para>These ioctls are optional, not all drivers may support
88them. They were introduced in Linux 2.6.21.</para>
89
90 <table pgwide="1" frame="none" id="v4l2-encoder-cmd">
91 <title>struct <structname>v4l2_encoder_cmd</structname></title>
92 <tgroup cols="3">
93 &cs-str;
94 <tbody valign="top">
95 <row>
96 <entry>__u32</entry>
97 <entry><structfield>cmd</structfield></entry>
98 <entry>The encoder command, see <xref linkend="encoder-cmds" />.</entry>
99 </row>
100 <row>
101 <entry>__u32</entry>
102 <entry><structfield>flags</structfield></entry>
103 <entry>Flags to go with the command, see <xref
104 linkend="encoder-flags" />. If no flags are defined for
105this command, drivers and applications must set this field to
106zero.</entry>
107 </row>
108 <row>
109 <entry>__u32</entry>
110 <entry><structfield>data</structfield>[8]</entry>
111 <entry>Reserved for future extensions. Drivers and
112applications must set the array to zero.</entry>
113 </row>
114 </tbody>
115 </tgroup>
116 </table>
117
118 <table pgwide="1" frame="none" id="encoder-cmds">
119 <title>Encoder Commands</title>
120 <tgroup cols="3">
121 &cs-def;
122 <tbody valign="top">
123 <row>
124 <entry><constant>V4L2_ENC_CMD_START</constant></entry>
125 <entry>0</entry>
126 <entry>Start the encoder. When the encoder is already
127running or paused, this command does nothing. No flags are defined for
128this command.</entry>
129 </row>
130 <row>
131 <entry><constant>V4L2_ENC_CMD_STOP</constant></entry>
132 <entry>1</entry>
133 <entry>Stop the encoder. When the
134<constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant> flag is set,
135encoding will continue until the end of the current <wordasword>Group
136Of Pictures</wordasword>, otherwise encoding will stop immediately.
137When the encoder is already stopped, this command does
138nothing.</entry>
139 </row>
140 <row>
141 <entry><constant>V4L2_ENC_CMD_PAUSE</constant></entry>
142 <entry>2</entry>
143 <entry>Pause the encoder. When the encoder has not been
144started yet, the driver will return an &EPERM;. When the encoder is
145already paused, this command does nothing. No flags are defined for
146this command.</entry>
147 </row>
148 <row>
149 <entry><constant>V4L2_ENC_CMD_RESUME</constant></entry>
150 <entry>3</entry>
151 <entry>Resume encoding after a PAUSE command. When the
152encoder has not been started yet, the driver will return an &EPERM;.
153When the encoder is already running, this command does nothing. No
154flags are defined for this command.</entry>
155 </row>
156 </tbody>
157 </tgroup>
158 </table>
159
160 <table pgwide="1" frame="none" id="encoder-flags">
161 <title>Encoder Command Flags</title>
162 <tgroup cols="3">
163 &cs-def;
164 <tbody valign="top">
165 <row>
166 <entry><constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant></entry>
167 <entry>0x0001</entry>
168 <entry>Stop encoding at the end of the current <wordasword>Group Of
169Pictures</wordasword>, rather than immediately.</entry>
170 </row>
171 </tbody>
172 </tgroup>
173 </table>
174 </refsect1>
175
176 <refsect1>
177 &return-value;
178
179 <variablelist>
180 <varlistentry>
181 <term><errorcode>EINVAL</errorcode></term>
182 <listitem>
183 <para>The driver does not support this ioctl, or the
184<structfield>cmd</structfield> field is invalid.</para>
185 </listitem>
186 </varlistentry>
187 <varlistentry>
188 <term><errorcode>EPERM</errorcode></term>
189 <listitem>
190 <para>The application sent a PAUSE or RESUME command when
191the encoder was not running.</para>
192 </listitem>
193 </varlistentry>
194 </variablelist>
195 </refsect1>
196</refentry>
197
198<!--
199Local Variables:
200mode: sgml
201sgml-parent-document: "v4l2.sgml"
202indent-tabs-mode: nil
203End:
204-->
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