mirror of https://gitee.com/openkylin/linux.git
112 lines
3.3 KiB
XML
112 lines
3.3 KiB
XML
<refentry id="vidioc-query-dv-timings">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_QUERY_DV_TIMINGS</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_QUERY_DV_TIMINGS</refname>
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<refname>VIDIOC_SUBDEV_QUERY_DV_TIMINGS</refname>
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<refpurpose>Sense the DV preset 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>struct v4l2_dv_timings *<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_QUERY_DV_TIMINGS, VIDIOC_SUBDEV_QUERY_DV_TIMINGS</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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<note>
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<title>Experimental</title>
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<para>This is an <link linkend="experimental"> experimental </link>
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interface and may change in the future.</para>
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</note>
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<para>The hardware may be able to detect the current DV timings
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automatically, similar to sensing the video standard. To do so, applications
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call <constant>VIDIOC_QUERY_DV_TIMINGS</constant> with a pointer to a
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&v4l2-dv-timings;. Once the hardware detects the timings, it will fill in the
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timings structure.
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If the timings could not be detected because there was no signal, then
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<errorcode>ENOLINK</errorcode> is returned. If a signal was detected, but
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it was unstable and the receiver could not lock to the signal, then
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<errorcode>ENOLCK</errorcode> is returned. If the receiver could lock to the signal,
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but the format is unsupported (e.g. because the pixelclock is out of range
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of the hardware capabilities), then the driver fills in whatever timings it
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could find and returns <errorcode>ERANGE</errorcode>. In that case the application
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can call &VIDIOC-DV-TIMINGS-CAP; to compare the found timings with the hardware's
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capabilities in order to give more precise feedback to the user.
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</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>ENODATA</errorcode></term>
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<listitem>
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<para>Digital video timings are not supported for this input or output.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ENOLINK</errorcode></term>
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<listitem>
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<para>No timings could be detected because no signal was found.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ENOLCK</errorcode></term>
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<listitem>
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<para>The signal was unstable and the hardware could not lock on to it.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ERANGE</errorcode></term>
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<listitem>
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<para>Timings were found, but they are out of range of the hardware
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capabilities.
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</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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