Documentation/DocBook/v4l/vidioc-g-modulator.xml - kernel/bruno - Git at Google

 <refentry id="vidioc-g-modulator">
   <refmeta>
     <refentrytitle>ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</refentrytitle>
     &manvol;
   </refmeta>

   <refnamediv>
     <refname>VIDIOC_G_MODULATOR</refname>
     <refname>VIDIOC_S_MODULATOR</refname>
     <refpurpose>Get or set modulator attributes</refpurpose>
   </refnamediv>

   <refsynopsisdiv>
     <funcsynopsis>
       <funcprototype>
 	<funcdef>int <function>ioctl</function></funcdef>
 	<paramdef>int <parameter>fd</parameter></paramdef>
 	<paramdef>int <parameter>request</parameter></paramdef>
 	<paramdef>struct v4l2_modulator
 *<parameter>argp</parameter></paramdef>
       </funcprototype>
     </funcsynopsis>
     <funcsynopsis>
       <funcprototype>
 	<funcdef>int <function>ioctl</function></funcdef>
 	<paramdef>int <parameter>fd</parameter></paramdef>
 	<paramdef>int <parameter>request</parameter></paramdef>
 	<paramdef>const struct v4l2_modulator
 *<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_G_MODULATOR, VIDIOC_S_MODULATOR</para>
 	</listitem>
       </varlistentry>
       <varlistentry>
 	<term><parameter>argp</parameter></term>
 	<listitem>
 	  <para></para>
 	</listitem>
       </varlistentry>
     </variablelist>
   </refsect1>

   <refsect1>
     <title>Description</title>

     <para>To query the attributes of a modulator applications initialize
 the <structfield>index</structfield> field and zero out the
 <structfield>reserved</structfield> array of a &v4l2-modulator; and
 call the <constant>VIDIOC_G_MODULATOR</constant> ioctl with a pointer
 to this structure. Drivers fill the rest of the structure or return an
 &EINVAL; when the index is out of bounds. To enumerate all modulators
 applications shall begin at index zero, incrementing by one until the
 driver returns <errorcode>EINVAL</errorcode>.</para>

     <para>Modulators have two writable properties, an audio
 modulation set and the radio frequency. To change the modulated audio
 subprograms, applications initialize the <structfield>index
 </structfield> and <structfield>txsubchans</structfield> fields and the
 <structfield>reserved</structfield> array and call the
 <constant>VIDIOC_S_MODULATOR</constant> ioctl. Drivers may choose a
 different audio modulation if the request cannot be satisfied. However
 this is a write-only ioctl, it does not return the actual audio
 modulation selected.</para>

     <para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl
 is available.</para>

     <table pgwide="1" frame="none" id="v4l2-modulator">
       <title>struct <structname>v4l2_modulator</structname></title>
       <tgroup cols="3">
 	&cs-str;
 	<tbody valign="top">
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>index</structfield></entry>
 	    <entry>Identifies the modulator, set by the
 application.</entry>
 	  </row>
 	  <row>
 	    <entry>__u8</entry>
 	    <entry><structfield>name</structfield>[32]</entry>
 	    <entry>Name of the modulator, a NUL-terminated ASCII
 string. This information is intended for the user.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>capability</structfield></entry>
 	    <entry>Modulator capability flags. No flags are defined
 for this field, the tuner flags in &v4l2-tuner;
 are used accordingly. The audio flags indicate the ability
 to encode audio subprograms. They will <emphasis>not</emphasis>
 change for example with the current video standard.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>rangelow</structfield></entry>
 	    <entry>The lowest tunable frequency in units of 62.5
 KHz, or if the <structfield>capability</structfield> flag
 <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 Hz.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>rangehigh</structfield></entry>
 	    <entry>The highest tunable frequency in units of 62.5
 KHz, or if the <structfield>capability</structfield> flag
 <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 Hz.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>txsubchans</structfield></entry>
 	    <entry>With this field applications can determine how
 audio sub-carriers shall be modulated. It contains a set of flags as
 defined in <xref linkend="modulator-txsubchans" />. Note the tuner
 <structfield>rxsubchans</structfield> flags are reused, but the
 semantics are different. Video output devices are assumed to have an
 analog or PCM audio input with 1-3 channels. The
 <structfield>txsubchans</structfield> flags select one or more
 channels for modulation, together with some audio subprogram
 indicator, for example a stereo pilot tone.</entry>
 	  </row>
 	  <row>
 	    <entry>__u32</entry>
 	    <entry><structfield>reserved</structfield>[4]</entry>
 	    <entry>Reserved for future extensions. Drivers and
 applications must set the array to zero.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>

     <table pgwide="1" frame="none" id="modulator-txsubchans">
       <title>Modulator Audio Transmission Flags</title>
       <tgroup cols="3">
 	&cs-def;
 	<tbody valign="top">
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_MONO</constant></entry>
 	    <entry>0x0001</entry>
 	    <entry>Modulate channel 1 as mono audio, when the input
 has more channels, a down-mix of channel 1 and 2. This flag does not
 combine with <constant>V4L2_TUNER_SUB_STEREO</constant> or
 <constant>V4L2_TUNER_SUB_LANG1</constant>.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_STEREO</constant></entry>
 	    <entry>0x0002</entry>
 	    <entry>Modulate channel 1 and 2 as left and right
 channel of a stereo audio signal. When the input has only one channel
 or two channels and <constant>V4L2_TUNER_SUB_SAP</constant> is also
 set, channel 1 is encoded as left and right channel. This flag does
 not combine with <constant>V4L2_TUNER_SUB_MONO</constant> or
 <constant>V4L2_TUNER_SUB_LANG1</constant>. When the driver does not
 support stereo audio it shall fall back to mono.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_LANG1</constant></entry>
 	    <entry>0x0008</entry>
 	    <entry>Modulate channel 1 and 2 as primary and secondary
 language of a bilingual audio signal. When the input has only one
 channel it is used for both languages. It is not possible to encode
 the primary or secondary language only. This flag does not combine
 with <constant>V4L2_TUNER_SUB_MONO</constant>,
 <constant>V4L2_TUNER_SUB_STEREO</constant> or
 <constant>V4L2_TUNER_SUB_SAP</constant>. If the hardware does not
 support the respective audio matrix, or the current video standard
 does not permit bilingual audio the
 <constant>VIDIOC_S_MODULATOR</constant> ioctl shall return an &EINVAL;
 and the driver shall fall back to mono or stereo mode.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_LANG2</constant></entry>
 	    <entry>0x0004</entry>
 	    <entry>Same effect as
 <constant>V4L2_TUNER_SUB_SAP</constant>.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_SAP</constant></entry>
 	    <entry>0x0004</entry>
 	    <entry>When combined with <constant>V4L2_TUNER_SUB_MONO
 </constant> the first channel is encoded as mono audio, the last
 channel as Second Audio Program. When the input has only one channel
 it is used for both audio tracks. When the input has three channels
 the mono track is a down-mix of channel 1 and 2. When combined with
 <constant>V4L2_TUNER_SUB_STEREO</constant> channel 1 and 2 are
 encoded as left and right stereo audio, channel 3 as Second Audio
 Program. When the input has only two channels, the first is encoded as
 left and right channel and the second as SAP. When the input has only
 one channel it is used for all audio tracks. It is not possible to
 encode a Second Audio Program only. This flag must combine with
 <constant>V4L2_TUNER_SUB_MONO</constant> or
 <constant>V4L2_TUNER_SUB_STEREO</constant>. If the hardware does not
 support the respective audio matrix, or the current video standard
 does not permit SAP the <constant>VIDIOC_S_MODULATOR</constant> ioctl
 shall return an &EINVAL; and driver shall fall back to mono or stereo
 mode.</entry>
 	  </row>
 	  <row>
 	    <entry><constant>V4L2_TUNER_SUB_RDS</constant></entry>
 	    <entry>0x0010</entry>
 	    <entry>Enable the RDS encoder for a radio FM transmitter.</entry>
 	  </row>
 	</tbody>
       </tgroup>
     </table>
   </refsect1>

   <refsect1>
     &return-value;

     <variablelist>
       <varlistentry>
 	<term><errorcode>EINVAL</errorcode></term>
 	<listitem>
 	  <para>The &v4l2-modulator;
 <structfield>index</structfield> is out of bounds.</para>
 	</listitem>
       </varlistentry>
     </variablelist>
   </refsect1>
 </refentry>

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	<refentry id="vidioc-g-modulator">
	<refmeta>
	<refentrytitle>ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</refentrytitle>
	&manvol;
	</refmeta>

	<refnamediv>
	<refname>VIDIOC_G_MODULATOR</refname>
	<refname>VIDIOC_S_MODULATOR</refname>
	<refpurpose>Get or set modulator attributes</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
	<funcsynopsis>
	<funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>struct v4l2_modulator
	*<parameter>argp</parameter></paramdef>
	</funcprototype>
	</funcsynopsis>
	<funcsynopsis>
	<funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>const struct v4l2_modulator
	*<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_G_MODULATOR, VIDIOC_S_MODULATOR</para>
	</listitem>
	</varlistentry>
	<varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	<para></para>
	</listitem>
	</varlistentry>
	</variablelist>
	</refsect1>

	<refsect1>
	<title>Description</title>

	<para>To query the attributes of a modulator applications initialize
	the <structfield>index</structfield> field and zero out the
	<structfield>reserved</structfield> array of a &v4l2-modulator; and
	call the <constant>VIDIOC_G_MODULATOR</constant> ioctl with a pointer
	to this structure. Drivers fill the rest of the structure or return an
	&EINVAL; when the index is out of bounds. To enumerate all modulators
	applications shall begin at index zero, incrementing by one until the
	driver returns <errorcode>EINVAL</errorcode>.</para>

	<para>Modulators have two writable properties, an audio
	modulation set and the radio frequency. To change the modulated audio
	subprograms, applications initialize the <structfield>index
	</structfield> and <structfield>txsubchans</structfield> fields and the
	<structfield>reserved</structfield> array and call the
	<constant>VIDIOC_S_MODULATOR</constant> ioctl. Drivers may choose a
	different audio modulation if the request cannot be satisfied. However
	this is a write-only ioctl, it does not return the actual audio
	modulation selected.</para>

	<para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl
	is available.</para>

	<table pgwide="1" frame="none" id="v4l2-modulator">
	<title>struct <structname>v4l2_modulator</structname></title>
	<tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	<row>
	<entry>__u32</entry>
	<entry><structfield>index</structfield></entry>
	<entry>Identifies the modulator, set by the
	application.</entry>
	</row>
	<row>
	<entry>__u8</entry>
	<entry><structfield>name</structfield>[32]</entry>
	<entry>Name of the modulator, a NUL-terminated ASCII
	string. This information is intended for the user.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>capability</structfield></entry>
	<entry>Modulator capability flags. No flags are defined
	for this field, the tuner flags in &v4l2-tuner;
	are used accordingly. The audio flags indicate the ability
	to encode audio subprograms. They will <emphasis>not</emphasis>
	change for example with the current video standard.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>rangelow</structfield></entry>
	<entry>The lowest tunable frequency in units of 62.5
	KHz, or if the <structfield>capability</structfield> flag
	<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
	Hz.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>rangehigh</structfield></entry>
	<entry>The highest tunable frequency in units of 62.5
	KHz, or if the <structfield>capability</structfield> flag
	<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
	Hz.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>txsubchans</structfield></entry>
	<entry>With this field applications can determine how
	audio sub-carriers shall be modulated. It contains a set of flags as
	defined in <xref linkend="modulator-txsubchans" />. Note the tuner
	<structfield>rxsubchans</structfield> flags are reused, but the
	semantics are different. Video output devices are assumed to have an
	analog or PCM audio input with 1-3 channels. The
	<structfield>txsubchans</structfield> flags select one or more
	channels for modulation, together with some audio subprogram
	indicator, for example a stereo pilot tone.</entry>
	</row>
	<row>
	<entry>__u32</entry>
	<entry><structfield>reserved</structfield>[4]</entry>
	<entry>Reserved for future extensions. Drivers and
	applications must set the array to zero.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<table pgwide="1" frame="none" id="modulator-txsubchans">
	<title>Modulator Audio Transmission Flags</title>
	<tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	<row>
	<entry><constant>V4L2_TUNER_SUB_MONO</constant></entry>
	<entry>0x0001</entry>
	<entry>Modulate channel 1 as mono audio, when the input
	has more channels, a down-mix of channel 1 and 2. This flag does not
	combine with <constant>V4L2_TUNER_SUB_STEREO</constant> or
	<constant>V4L2_TUNER_SUB_LANG1</constant>.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_STEREO</constant></entry>
	<entry>0x0002</entry>
	<entry>Modulate channel 1 and 2 as left and right
	channel of a stereo audio signal. When the input has only one channel
	or two channels and <constant>V4L2_TUNER_SUB_SAP</constant> is also
	set, channel 1 is encoded as left and right channel. This flag does
	not combine with <constant>V4L2_TUNER_SUB_MONO</constant> or
	<constant>V4L2_TUNER_SUB_LANG1</constant>. When the driver does not
	support stereo audio it shall fall back to mono.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_LANG1</constant></entry>
	<entry>0x0008</entry>
	<entry>Modulate channel 1 and 2 as primary and secondary
	language of a bilingual audio signal. When the input has only one
	channel it is used for both languages. It is not possible to encode
	the primary or secondary language only. This flag does not combine
	with <constant>V4L2_TUNER_SUB_MONO</constant>,
	<constant>V4L2_TUNER_SUB_STEREO</constant> or
	<constant>V4L2_TUNER_SUB_SAP</constant>. If the hardware does not
	support the respective audio matrix, or the current video standard
	does not permit bilingual audio the
	<constant>VIDIOC_S_MODULATOR</constant> ioctl shall return an &EINVAL;
	and the driver shall fall back to mono or stereo mode.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_LANG2</constant></entry>
	<entry>0x0004</entry>
	<entry>Same effect as
	<constant>V4L2_TUNER_SUB_SAP</constant>.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_SAP</constant></entry>
	<entry>0x0004</entry>
	<entry>When combined with <constant>V4L2_TUNER_SUB_MONO
	</constant> the first channel is encoded as mono audio, the last
	channel as Second Audio Program. When the input has only one channel
	it is used for both audio tracks. When the input has three channels
	the mono track is a down-mix of channel 1 and 2. When combined with
	<constant>V4L2_TUNER_SUB_STEREO</constant> channel 1 and 2 are
	encoded as left and right stereo audio, channel 3 as Second Audio
	Program. When the input has only two channels, the first is encoded as
	left and right channel and the second as SAP. When the input has only
	one channel it is used for all audio tracks. It is not possible to
	encode a Second Audio Program only. This flag must combine with
	<constant>V4L2_TUNER_SUB_MONO</constant> or
	<constant>V4L2_TUNER_SUB_STEREO</constant>. If the hardware does not
	support the respective audio matrix, or the current video standard
	does not permit SAP the <constant>VIDIOC_S_MODULATOR</constant> ioctl
	shall return an &EINVAL; and driver shall fall back to mono or stereo
	mode.</entry>
	</row>
	<row>
	<entry><constant>V4L2_TUNER_SUB_RDS</constant></entry>
	<entry>0x0010</entry>
	<entry>Enable the RDS encoder for a radio FM transmitter.</entry>
	</row>
	</tbody>
	</tgroup>
	</table>
	</refsect1>

	<refsect1>
	&return-value;

	<variablelist>
	<varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	<para>The &v4l2-modulator;
	<structfield>index</structfield> is out of bounds.</para>
	</listitem>
	</varlistentry>
	</variablelist>
	</refsect1>
	</refentry>

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