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Mauro Carvalho Chehab8e080c22009-09-13 22:16:04 -03001<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
Mauro Carvalho Chehab8e080c22009-09-13 22:16:04 -030052 <para>These ioctls control an audio/video (usually MPEG-) encoder.
53<constant>VIDIOC_ENCODER_CMD</constant> sends a command to the
54encoder, <constant>VIDIOC_TRY_ENCODER_CMD</constant> can be used to
55try a command without actually executing it.</para>
56
57 <para>To send a command applications must initialize all fields of a
58 &v4l2-encoder-cmd; and call
59 <constant>VIDIOC_ENCODER_CMD</constant> or
60 <constant>VIDIOC_TRY_ENCODER_CMD</constant> with a pointer to this
61 structure.</para>
62
63 <para>The <structfield>cmd</structfield> field must contain the
64command code. The <structfield>flags</structfield> field is currently
65only used by the STOP command and contains one bit: If the
66<constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant> flag is set,
67encoding will continue until the end of the current <wordasword>Group
68Of Pictures</wordasword>, otherwise it will stop immediately.</para>
69
Hans Verkuil6b4f1252011-11-24 09:55:53 -030070 <para>A <function>read</function>() or &VIDIOC-STREAMON; call sends an implicit
71START command to the encoder if it has not been started yet. After a STOP command,
Mauro Carvalho Chehab8e080c22009-09-13 22:16:04 -030072<function>read</function>() calls will read the remaining data
73buffered by the driver. When the buffer is empty,
74<function>read</function>() will return zero and the next
75<function>read</function>() call will restart the encoder.</para>
76
Hans Verkuil6b4f1252011-11-24 09:55:53 -030077 <para>A <function>close</function>() or &VIDIOC-STREAMOFF; call of a streaming
78file descriptor sends an implicit immediate STOP to the encoder, and all buffered
79data is discarded.</para>
Mauro Carvalho Chehab8e080c22009-09-13 22:16:04 -030080
81 <para>These ioctls are optional, not all drivers may support
82them. They were introduced in Linux 2.6.21.</para>
83
84 <table pgwide="1" frame="none" id="v4l2-encoder-cmd">
85 <title>struct <structname>v4l2_encoder_cmd</structname></title>
86 <tgroup cols="3">
87 &cs-str;
88 <tbody valign="top">
89 <row>
90 <entry>__u32</entry>
91 <entry><structfield>cmd</structfield></entry>
92 <entry>The encoder command, see <xref linkend="encoder-cmds" />.</entry>
93 </row>
94 <row>
95 <entry>__u32</entry>
96 <entry><structfield>flags</structfield></entry>
97 <entry>Flags to go with the command, see <xref
98 linkend="encoder-flags" />. If no flags are defined for
99this command, drivers and applications must set this field to
100zero.</entry>
101 </row>
102 <row>
103 <entry>__u32</entry>
104 <entry><structfield>data</structfield>[8]</entry>
105 <entry>Reserved for future extensions. Drivers and
106applications must set the array to zero.</entry>
107 </row>
108 </tbody>
109 </tgroup>
110 </table>
111
112 <table pgwide="1" frame="none" id="encoder-cmds">
113 <title>Encoder Commands</title>
114 <tgroup cols="3">
115 &cs-def;
116 <tbody valign="top">
117 <row>
118 <entry><constant>V4L2_ENC_CMD_START</constant></entry>
119 <entry>0</entry>
120 <entry>Start the encoder. When the encoder is already
121running or paused, this command does nothing. No flags are defined for
122this command.</entry>
123 </row>
124 <row>
125 <entry><constant>V4L2_ENC_CMD_STOP</constant></entry>
126 <entry>1</entry>
127 <entry>Stop the encoder. When the
128<constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant> flag is set,
129encoding will continue until the end of the current <wordasword>Group
130Of Pictures</wordasword>, otherwise encoding will stop immediately.
131When the encoder is already stopped, this command does
132nothing.</entry>
133 </row>
134 <row>
135 <entry><constant>V4L2_ENC_CMD_PAUSE</constant></entry>
136 <entry>2</entry>
137 <entry>Pause the encoder. When the encoder has not been
138started yet, the driver will return an &EPERM;. When the encoder is
139already paused, this command does nothing. No flags are defined for
140this command.</entry>
141 </row>
142 <row>
143 <entry><constant>V4L2_ENC_CMD_RESUME</constant></entry>
144 <entry>3</entry>
145 <entry>Resume encoding after a PAUSE command. When the
146encoder has not been started yet, the driver will return an &EPERM;.
147When the encoder is already running, this command does nothing. No
148flags are defined for this command.</entry>
149 </row>
150 </tbody>
151 </tgroup>
152 </table>
153
154 <table pgwide="1" frame="none" id="encoder-flags">
155 <title>Encoder Command Flags</title>
156 <tgroup cols="3">
157 &cs-def;
158 <tbody valign="top">
159 <row>
160 <entry><constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant></entry>
161 <entry>0x0001</entry>
162 <entry>Stop encoding at the end of the current <wordasword>Group Of
163Pictures</wordasword>, rather than immediately.</entry>
164 </row>
165 </tbody>
166 </tgroup>
167 </table>
168 </refsect1>
169
170 <refsect1>
171 &return-value;
172
173 <variablelist>
174 <varlistentry>
175 <term><errorcode>EINVAL</errorcode></term>
176 <listitem>
Mauro Carvalho Chehab43c1daa2011-07-05 11:22:28 -0300177 <para>The <structfield>cmd</structfield> field is invalid.</para>
Mauro Carvalho Chehab8e080c22009-09-13 22:16:04 -0300178 </listitem>
179 </varlistentry>
180 <varlistentry>
181 <term><errorcode>EPERM</errorcode></term>
182 <listitem>
183 <para>The application sent a PAUSE or RESUME command when
184the encoder was not running.</para>
185 </listitem>
186 </varlistentry>
187 </variablelist>
188 </refsect1>
189</refentry>