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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

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	    <para>These ioctls control an audio/video (usually MPEG-) encoder.
53	<constant>VIDIOC_ENCODER_CMD</constant> sends a command to the
54	encoder, <constant>VIDIOC_TRY_ENCODER_CMD</constant> can be used to
55	try 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
64	command code. The <structfield>flags</structfield> field is currently
65	only used by the STOP command and contains one bit: If the
66	<constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant> flag is set,
67	encoding will continue until the end of the current <wordasword>Group
68	Of Pictures</wordasword>, otherwise it will stop immediately.</para>
69	
70	    <para>A <function>read</function>() or &VIDIOC-STREAMON; call sends an implicit
71	START command to the encoder if it has not been started yet. After a STOP command,
72	<function>read</function>() calls will read the remaining data
73	buffered 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	
77	    <para>A <function>close</function>() or &VIDIOC-STREAMOFF; call of a streaming
78	file descriptor sends an implicit immediate STOP to the encoder, and all buffered
79	data is discarded.</para>
80	
81	    <para>These ioctls are optional, not all drivers may support
82	them. 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
99	this command, drivers and applications must set this field to
100	zero.</entry>
101		  </row>
102		  <row>
103		    <entry>__u32</entry>
104		    <entry><structfield>data</structfield>[8]</entry>
105		    <entry>Reserved for future extensions. Drivers and
106	applications 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
121	running or paused, this command does nothing. No flags are defined for
122	this 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,
129	encoding will continue until the end of the current <wordasword>Group
130	Of Pictures</wordasword>, otherwise encoding will stop immediately.
131	When the encoder is already stopped, this command does
132	nothing.</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
138	started yet, the driver will return an &EPERM;. When the encoder is
139	already paused, this command does nothing. No flags are defined for
140	this 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
146	encoder has not been started yet, the driver will return an &EPERM;.
147	When the encoder is already running, this command does nothing. No
148	flags 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
163	Pictures</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>
177		  <para>The <structfield>cmd</structfield> field is invalid.</para>
178		</listitem>
179	      </varlistentry>
180	      <varlistentry>
181		<term><errorcode>EPERM</errorcode></term>
182		<listitem>
183		  <para>The application sent a PAUSE or RESUME command when
184	the encoder was not running.</para>
185		</listitem>
186	      </varlistentry>
187	    </variablelist>
188	  </refsect1>
189	</refentry>
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