mirror of https://gitee.com/openkylin/linux.git
90 lines
2.2 KiB
XML
90 lines
2.2 KiB
XML
<refentry id="vidioc-querystd">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_QUERYSTD</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_QUERYSTD</refname>
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<refpurpose>Sense the video standard received by the current
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input</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>v4l2_std_id *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>VIDIOC_QUERYSTD</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>The hardware may be able to detect the current video
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standard automatically. To do so, applications call <constant>
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VIDIOC_QUERYSTD</constant> with a pointer to a &v4l2-std-id; type. The
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driver stores here a set of candidates, this can be a single flag or a
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set of supported standards if for example the hardware can only
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distinguish between 50 and 60 Hz systems. When detection is not
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possible or fails, the set must contain all standards supported by the
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current video input or output.</para>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>This ioctl is not supported.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EBUSY</errorcode></term>
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<listitem>
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<para>The device is busy and therefore can not detect the standard</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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<!--
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Local Variables:
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mode: sgml
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sgml-parent-document: "v4l2.sgml"
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indent-tabs-mode: nil
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End:
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-->
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