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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 | ||
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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 | ||
6b4f1252 HV |
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, | |
8e080c2e MCC |
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 | ||
6b4f1252 HV |
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> | |
8e080c2e MCC |
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> | |
43c1daa4 | 177 | <para>The <structfield>cmd</structfield> field is invalid.</para> |
8e080c2e MCC |
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> |