198 lines
6.7 KiB
XML
198 lines
6.7 KiB
XML
<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. mem2mem encoders will send a <constant>V4L2_EVENT_EOS</constant> event
|
|
when the last frame has been encoded and all frames are ready to be dequeued and
|
|
will set the <constant>V4L2_BUF_FLAG_LAST</constant> buffer flag on the last
|
|
buffer of the capture queue to indicate there will be no new buffers produced to
|
|
dequeue. This buffer may be empty, indicated by the driver setting the
|
|
<structfield>bytesused</structfield> field to 0. Once the
|
|
<constant>V4L2_BUF_FLAG_LAST</constant> flag was set, the
|
|
<link linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl will not block anymore,
|
|
but return an &EPIPE;.</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>
|