107 lines
3.3 KiB
XML
107 lines
3.3 KiB
XML
|
<refentry id="vidioc-streamon">
|
||
|
|
<refmeta>
|
||
|
|
<refentrytitle>ioctl VIDIOC_STREAMON, VIDIOC_STREAMOFF</refentrytitle>
|
||
|
|
&manvol;
|
||
|
|
</refmeta>
|
||
|
|
|
||
|
|
<refnamediv>
|
||
|
|
<refname>VIDIOC_STREAMON</refname>
|
||
|
|
<refname>VIDIOC_STREAMOFF</refname>
|
||
|
|
<refpurpose>Start or stop streaming I/O</refpurpose>
|
||
|
|
</refnamediv>
|
||
|
|
|
||
|
|
<refsynopsisdiv>
|
||
|
|
<funcsynopsis>
|
||
|
|
<funcprototype>
|
||
|
|
<funcdef>int <function>ioctl</function></funcdef>
|
||
|
|
<paramdef>int <parameter>fd</parameter></paramdef>
|
||
|
|
<paramdef>int <parameter>request</parameter></paramdef>
|
||
|
|
<paramdef>const int *<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_STREAMON, VIDIOC_STREAMOFF</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><parameter>argp</parameter></term>
|
||
|
|
<listitem>
|
||
|
|
<para></para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
</variablelist>
|
||
|
|
</refsect1>
|
||
|
|
|
||
|
|
<refsect1>
|
||
|
|
<title>Description</title>
|
||
|
|
|
||
|
|
<para>The <constant>VIDIOC_STREAMON</constant> and
|
||
|
|
<constant>VIDIOC_STREAMOFF</constant> ioctl start and stop the capture
|
||
|
|
or output process during streaming (<link linkend="mmap">memory
|
||
|
|
mapping</link> or <link linkend="userp">user pointer</link>) I/O.</para>
|
||
|
|
|
||
|
|
<para>Specifically the capture hardware is disabled and no input
|
||
|
|
buffers are filled (if there are any empty buffers in the incoming
|
||
|
|
queue) until <constant>VIDIOC_STREAMON</constant> has been called.
|
||
|
|
Accordingly the output hardware is disabled, no video signal is
|
||
|
|
produced until <constant>VIDIOC_STREAMON</constant> has been called.
|
||
|
|
The ioctl will succeed only when at least one output buffer is in the
|
||
|
|
incoming queue.</para>
|
||
|
|
|
||
|
|
<para>The <constant>VIDIOC_STREAMOFF</constant> ioctl, apart of
|
||
|
|
aborting or finishing any DMA in progress, unlocks any user pointer
|
||
|
|
buffers locked in physical memory, and it removes all buffers from the
|
||
|
|
incoming and outgoing queues. That means all images captured but not
|
||
|
|
dequeued yet will be lost, likewise all images enqueued for output but
|
||
|
|
not transmitted yet. I/O returns to the same state as after calling
|
||
|
|
&VIDIOC-REQBUFS; and can be restarted accordingly.</para>
|
||
|
|
|
||
|
|
<para>Both ioctls take a pointer to an integer, the desired buffer or
|
||
|
|
stream type. This is the same as &v4l2-requestbuffers;
|
||
|
|
<structfield>type</structfield>.</para>
|
||
|
|
|
||
|
|
<para>Note applications can be preempted for unknown periods right
|
||
|
|
before or after the <constant>VIDIOC_STREAMON</constant> or
|
||
|
|
<constant>VIDIOC_STREAMOFF</constant> calls, there is no notion of
|
||
|
|
starting or stopping "now". Buffer timestamps can be used to
|
||
|
|
synchronize with other events.</para>
|
||
|
|
</refsect1>
|
||
|
|
|
||
|
|
<refsect1>
|
||
|
|
&return-value;
|
||
|
|
|
||
|
|
<variablelist>
|
||
|
|
<varlistentry>
|
||
|
|
<term><errorcode>EINVAL</errorcode></term>
|
||
|
|
<listitem>
|
||
|
|
<para>Streaming I/O is not supported, the buffer
|
||
|
|
<structfield>type</structfield> is not supported, or no buffers have
|
||
|
|
been allocated (memory mapping) or enqueued (output) yet.</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
</variablelist>
|
||
|
|
</refsect1>
|
||
|
|
</refentry>
|
||
|
|
|
||
|
|
<!--
|
||
|
|
Local Variables:
|
||
|
|
mode: sgml
|
||
|
|
sgml-parent-document: "v4l2.sgml"
|
||
|
|
indent-tabs-mode: nil
|
||
|
|
End:
|
||
|
|
-->
|