182 lines
6.4 KiB
XML
182 lines
6.4 KiB
XML
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<refentry id="vidioc-enum-freq-bands">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_ENUM_FREQ_BANDS</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_ENUM_FREQ_BANDS</refname>
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<refpurpose>Enumerate supported frequency bands</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_frequency_band
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*<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_ENUM_FREQ_BANDS</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>Enumerates the frequency bands that a tuner or modulator supports.
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To do this applications initialize the <structfield>tuner</structfield>,
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<structfield>type</structfield> and <structfield>index</structfield> fields,
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and zero out the <structfield>reserved</structfield> array of a &v4l2-frequency-band; and
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call the <constant>VIDIOC_ENUM_FREQ_BANDS</constant> ioctl with a pointer
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to this structure.</para>
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<para>This ioctl is supported if the <constant>V4L2_TUNER_CAP_FREQ_BANDS</constant> capability
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of the corresponding tuner/modulator is set.</para>
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<table pgwide="1" frame="none" id="v4l2-frequency-band">
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<title>struct <structname>v4l2_frequency_band</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>tuner</structfield></entry>
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<entry>The tuner or modulator index number. This is the
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same value as in the &v4l2-input; <structfield>tuner</structfield>
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field and the &v4l2-tuner; <structfield>index</structfield> field, or
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the &v4l2-output; <structfield>modulator</structfield> field and the
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&v4l2-modulator; <structfield>index</structfield> field.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>type</structfield></entry>
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<entry>The tuner type. This is the same value as in the
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&v4l2-tuner; <structfield>type</structfield> field. The type must be set
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to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
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device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
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for all others. Set this field to <constant>V4L2_TUNER_RADIO</constant> for
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modulators (currently only radio modulators are supported).
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See <xref linkend="v4l2-tuner-type" /></entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>index</structfield></entry>
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<entry>Identifies the frequency band, set by the application.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>capability</structfield></entry>
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<entry spanname="hspan">The tuner/modulator capability flags for
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this frequency band, see <xref linkend="tuner-capability" />. The <constant>V4L2_TUNER_CAP_LOW</constant>
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or <constant>V4L2_TUNER_CAP_1HZ</constant> capability must be the same for all frequency bands of the selected tuner/modulator.
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So either all bands have that capability set, or none of them have that capability.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>rangelow</structfield></entry>
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<entry spanname="hspan">The lowest tunable frequency in
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units of 62.5 kHz, or if the <structfield>capability</structfield>
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flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
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Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
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<constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>rangehigh</structfield></entry>
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<entry spanname="hspan">The highest tunable frequency in
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units of 62.5 kHz, or if the <structfield>capability</structfield>
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flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
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Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
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<constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>modulation</structfield></entry>
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<entry spanname="hspan">The supported modulation systems of this frequency band.
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See <xref linkend="band-modulation" />. Note that currently only one
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modulation system per frequency band is supported. More work will need to
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be done if multiple modulation systems are possible. Contact the
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linux-media mailing list (&v4l-ml;) if you need that functionality.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>reserved</structfield>[9]</entry>
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<entry>Reserved for future extensions. Applications and drivers
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must set the array to zero.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="band-modulation">
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<title>Band Modulation Systems</title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_BAND_MODULATION_VSB</constant></entry>
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<entry>0x02</entry>
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<entry>Vestigial Sideband modulation, used for analog TV.</entry>
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</row>
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<row>
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<entry><constant>V4L2_BAND_MODULATION_FM</constant></entry>
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<entry>0x04</entry>
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<entry>Frequency Modulation, commonly used for analog radio.</entry>
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</row>
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<row>
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<entry><constant>V4L2_BAND_MODULATION_AM</constant></entry>
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<entry>0x08</entry>
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<entry>Amplitude Modulation, commonly used for analog radio.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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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>The <structfield>tuner</structfield> or <structfield>index</structfield>
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is out of bounds or the <structfield>type</structfield> field is wrong.</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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