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-<refentry id="vidioc-querystd">
- <refmeta>
- <refentrytitle>ioctl VIDIOC_QUERYSTD</refentrytitle>
- &manvol;
- </refmeta>
-
- <refnamediv>
- <refname>VIDIOC_QUERYSTD</refname>
- <refpurpose>Sense the video standard received by the current
-input</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcprototype>
- <funcdef>int <function>ioctl</function></funcdef>
- <paramdef>int <parameter>fd</parameter></paramdef>
- <paramdef>int <parameter>request</parameter></paramdef>
- <paramdef>v4l2_std_id *<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_QUERYSTD</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><parameter>argp</parameter></term>
- <listitem>
- <para></para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>Description</title>
-
- <para>The hardware may be able to detect the current video
-standard automatically. To do so, applications call <constant>
-VIDIOC_QUERYSTD</constant> with a pointer to a &v4l2-std-id; type. The
-driver stores here a set of candidates, this can be a single flag or a
-set of supported standards if for example the hardware can only
-distinguish between 50 and 60 Hz systems. If no signal was detected,
-then the driver will return V4L2_STD_UNKNOWN. When detection is not
-possible or fails, the set must contain all standards supported by the
-current video input or output.</para>
-
-<para>Please note that drivers shall <emphasis>not</emphasis> switch the video standard
-automatically if a new video standard is detected. Instead, drivers should send the
-<constant>V4L2_EVENT_SOURCE_CHANGE</constant> event (if they support this) and expect
-that userspace will take action by calling <constant>VIDIOC_QUERYSTD</constant>.
-The reason is that a new video standard can mean different buffer sizes as well, and you
-cannot change buffer sizes on the fly. In general, applications that receive the
-Source Change event will have to call <constant>VIDIOC_QUERYSTD</constant>,
-and if the detected video standard is valid they will have to stop streaming, set the new
-standard, allocate new buffers and start streaming again.</para>
-
- </refsect1>
-
- <refsect1>
- &return-value;
- <variablelist>
- <varlistentry>
- <term><errorcode>ENODATA</errorcode></term>
- <listitem>
- <para>Standard video timings are not supported for this input or output.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-</refentry>