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+<refentry id="vidioc-encoder-cmd">
+ <refmeta>
+ <refentrytitle>ioctl VIDIOC_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD</refentrytitle>
+ &manvol;
+ </refmeta>
+
+ <refnamediv>
+ <refname>VIDIOC_ENCODER_CMD</refname>
+ <refname>VIDIOC_TRY_ENCODER_CMD</refname>
+ <refpurpose>Execute an encoder command</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>int <function>ioctl</function></funcdef>
+ <paramdef>int <parameter>fd</parameter></paramdef>
+ <paramdef>int <parameter>request</parameter></paramdef>
+ <paramdef>struct v4l2_encoder_cmd *<parameter>argp</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Arguments</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><parameter>fd</parameter></term>
+ <listitem>
+ <para>&fd;</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>request</parameter></term>
+ <listitem>
+ <para>VIDIOC_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>argp</parameter></term>
+ <listitem>
+ <para></para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>These ioctls control an audio/video (usually MPEG-) encoder.
+<constant>VIDIOC_ENCODER_CMD</constant> sends a command to the
+encoder, <constant>VIDIOC_TRY_ENCODER_CMD</constant> can be used to
+try a command without actually executing it.</para>
+
+ <para>To send a command applications must initialize all fields of a
+ &v4l2-encoder-cmd; and call
+ <constant>VIDIOC_ENCODER_CMD</constant> or
+ <constant>VIDIOC_TRY_ENCODER_CMD</constant> with a pointer to this
+ structure.</para>
+
+ <para>The <structfield>cmd</structfield> field must contain the
+command code. The <structfield>flags</structfield> field is currently
+only used by the STOP command and contains one bit: If the
+<constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant> flag is set,
+encoding will continue until the end of the current <wordasword>Group
+Of Pictures</wordasword>, otherwise it will stop immediately.</para>
+
+ <para>A <function>read</function>() or &VIDIOC-STREAMON; call sends an implicit
+START command to the encoder if it has not been started yet. After a STOP command,
+<function>read</function>() calls will read the remaining data
+buffered by the driver. When the buffer is empty,
+<function>read</function>() will return zero and the next
+<function>read</function>() call will restart the encoder.</para>
+
+ <para>A <function>close</function>() or &VIDIOC-STREAMOFF; call of a streaming
+file descriptor sends an implicit immediate STOP to the encoder, and all buffered
+data is discarded.</para>
+
+ <para>These ioctls are optional, not all drivers may support
+them. They were introduced in Linux 2.6.21.</para>
+
+ <table pgwide="1" frame="none" id="v4l2-encoder-cmd">
+ <title>struct <structname>v4l2_encoder_cmd</structname></title>
+ <tgroup cols="3">
+ &cs-str;
+ <tbody valign="top">
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>cmd</structfield></entry>
+ <entry>The encoder command, see <xref linkend="encoder-cmds" />.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>flags</structfield></entry>
+ <entry>Flags to go with the command, see <xref
+ linkend="encoder-flags" />. If no flags are defined for
+this command, drivers and applications must set this field to
+zero.</entry>
+ </row>
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>data</structfield>[8]</entry>
+ <entry>Reserved for future extensions. Drivers and
+applications must set the array to zero.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <table pgwide="1" frame="none" id="encoder-cmds">
+ <title>Encoder Commands</title>
+ <tgroup cols="3">
+ &cs-def;
+ <tbody valign="top">
+ <row>
+ <entry><constant>V4L2_ENC_CMD_START</constant></entry>
+ <entry>0</entry>
+ <entry>Start the encoder. When the encoder is already
+running or paused, this command does nothing. No flags are defined for
+this command.</entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_ENC_CMD_STOP</constant></entry>
+ <entry>1</entry>
+ <entry>Stop the encoder. When the
+<constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant> flag is set,
+encoding will continue until the end of the current <wordasword>Group
+Of Pictures</wordasword>, otherwise encoding will stop immediately.
+When the encoder is already stopped, this command does
+nothing.</entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_ENC_CMD_PAUSE</constant></entry>
+ <entry>2</entry>
+ <entry>Pause the encoder. When the encoder has not been
+started yet, the driver will return an &EPERM;. When the encoder is
+already paused, this command does nothing. No flags are defined for
+this command.</entry>
+ </row>
+ <row>
+ <entry><constant>V4L2_ENC_CMD_RESUME</constant></entry>
+ <entry>3</entry>
+ <entry>Resume encoding after a PAUSE command. When the
+encoder has not been started yet, the driver will return an &EPERM;.
+When the encoder is already running, this command does nothing. No
+flags are defined for this command.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <table pgwide="1" frame="none" id="encoder-flags">
+ <title>Encoder Command Flags</title>
+ <tgroup cols="3">
+ &cs-def;
+ <tbody valign="top">
+ <row>
+ <entry><constant>V4L2_ENC_CMD_STOP_AT_GOP_END</constant></entry>
+ <entry>0x0001</entry>
+ <entry>Stop encoding at the end of the current <wordasword>Group Of
+Pictures</wordasword>, rather than immediately.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </refsect1>
+
+ <refsect1>
+ &return-value;
+
+ <variablelist>
+ <varlistentry>
+ <term><errorcode>EINVAL</errorcode></term>
+ <listitem>
+ <para>The <structfield>cmd</structfield> field is invalid.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>EPERM</errorcode></term>
+ <listitem>
+ <para>The application sent a PAUSE or RESUME command when
+the encoder was not running.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+</refentry>