Documentation/DocBook/media/v4l/vidioc-g-modulator.xml

   1 <refentry id="vidioc-g-modulator">
   2   <refmeta>
   3     <refentrytitle>ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>VIDIOC_G_MODULATOR</refname>
   9     <refname>VIDIOC_S_MODULATOR</refname>
  10     <refpurpose>Get or set modulator attributes</refpurpose>
  11   </refnamediv>
  12
  13   <refsynopsisdiv>
  14     <funcsynopsis>
  15       <funcprototype>
  16         <funcdef>int <function>ioctl</function></funcdef>
  17         <paramdef>int <parameter>fd</parameter></paramdef>
  18         <paramdef>int <parameter>request</parameter></paramdef>
  19         <paramdef>struct v4l2_modulator
  20 *<parameter>argp</parameter></paramdef>
  21       </funcprototype>
  22     </funcsynopsis>
  23     <funcsynopsis>
  24       <funcprototype>
  25         <funcdef>int <function>ioctl</function></funcdef>
  26         <paramdef>int <parameter>fd</parameter></paramdef>
  27         <paramdef>int <parameter>request</parameter></paramdef>
  28         <paramdef>const struct v4l2_modulator
  29 *<parameter>argp</parameter></paramdef>
  30       </funcprototype>
  31     </funcsynopsis>
  32   </refsynopsisdiv>
  33
  34   <refsect1>
  35     <title>Arguments</title>
  36
  37     <variablelist>
  38       <varlistentry>
  39         <term><parameter>fd</parameter></term>
  40         <listitem>
  41           <para>&fd;</para>
  42         </listitem>
  43       </varlistentry>
  44       <varlistentry>
  45         <term><parameter>request</parameter></term>
  46         <listitem>
  47           <para>VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR</para>
  48         </listitem>
  49       </varlistentry>
  50       <varlistentry>
  51         <term><parameter>argp</parameter></term>
  52         <listitem>
  53           <para></para>
  54         </listitem>
  55       </varlistentry>
  56     </variablelist>
  57   </refsect1>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para>To query the attributes of a modulator applications initialize
  63 the <structfield>index</structfield> field and zero out the
  64 <structfield>reserved</structfield> array of a &v4l2-modulator; and
  65 call the <constant>VIDIOC_G_MODULATOR</constant> ioctl with a pointer
  66 to this structure. Drivers fill the rest of the structure or return an
  67 &EINVAL; when the index is out of bounds. To enumerate all modulators
  68 applications shall begin at index zero, incrementing by one until the
  69 driver returns <errorcode>EINVAL</errorcode>.</para>
  70
  71     <para>Modulators have two writable properties, an audio
  72 modulation set and the radio frequency. To change the modulated audio
  73 subprograms, applications initialize the <structfield>index
  74 </structfield> and <structfield>txsubchans</structfield> fields and the
  75 <structfield>reserved</structfield> array and call the
  76 <constant>VIDIOC_S_MODULATOR</constant> ioctl. Drivers may choose a
  77 different audio modulation if the request cannot be satisfied. However
  78 this is a write-only ioctl, it does not return the actual audio
  79 modulation selected.</para>
  80
  81     <para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl
  82 is available.</para>
  83
  84     <table pgwide="1" frame="none" id="v4l2-modulator">
  85       <title>struct <structname>v4l2_modulator</structname></title>
  86       <tgroup cols="3">
  87         &cs-str;
  88         <tbody valign="top">
  89           <row>
  90             <entry>__u32</entry>
  91             <entry><structfield>index</structfield></entry>
  92             <entry>Identifies the modulator, set by the
  93 application.</entry>
  94           </row>
  95           <row>
  96             <entry>__u8</entry>
  97             <entry><structfield>name</structfield>[32]</entry>
  98             <entry>Name of the modulator, a NUL-terminated ASCII
  99 string. This information is intended for the user.</entry>
 100           </row>
 101           <row>
 102             <entry>__u32</entry>
 103             <entry><structfield>capability</structfield></entry>
 104             <entry>Modulator capability flags. No flags are defined
 105 for this field, the tuner flags in &v4l2-tuner;
 106 are used accordingly. The audio flags indicate the ability
 107 to encode audio subprograms. They will <emphasis>not</emphasis>
 108 change for example with the current video standard.</entry>
 109           </row>
 110           <row>
 111             <entry>__u32</entry>
 112             <entry><structfield>rangelow</structfield></entry>
 113             <entry>The lowest tunable frequency in units of 62.5
 114 KHz, or if the <structfield>capability</structfield> flag
 115 <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 116 Hz, or if the <structfield>capability</structfield> flag
 117 <constant>V4L2_TUNER_CAP_1HZ</constant> is set, in units of 1 Hz.</entry>
 118           </row>
 119           <row>
 120             <entry>__u32</entry>
 121             <entry><structfield>rangehigh</structfield></entry>
 122             <entry>The highest tunable frequency in units of 62.5
 123 KHz, or if the <structfield>capability</structfield> flag
 124 <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
 125 Hz, or if the <structfield>capability</structfield> flag
 126 <constant>V4L2_TUNER_CAP_1HZ</constant> is set, in units of 1 Hz.</entry>
 127           </row>
 128           <row>
 129             <entry>__u32</entry>
 130             <entry><structfield>txsubchans</structfield></entry>
 131             <entry>With this field applications can determine how
 132 audio sub-carriers shall be modulated. It contains a set of flags as
 133 defined in <xref linkend="modulator-txsubchans" />. Note the tuner
 134 <structfield>rxsubchans</structfield> flags are reused, but the
 135 semantics are different. Video output devices are assumed to have an
 136 analog or PCM audio input with 1-3 channels. The
 137 <structfield>txsubchans</structfield> flags select one or more
 138 channels for modulation, together with some audio subprogram
 139 indicator, for example a stereo pilot tone.</entry>
 140           </row>
 141           <row>
 142             <entry>__u32</entry>
 143             <entry><structfield>type</structfield></entry>
 144             <entry spanname="hspan">Type of the modulator, see <xref
 145                 linkend="v4l2-tuner-type" />.</entry>
 146           </row>
 147           <row>
 148             <entry>__u32</entry>
 149             <entry><structfield>reserved</structfield>[3]</entry>
 150             <entry>Reserved for future extensions. Drivers and
 151 applications must set the array to zero.</entry>
 152           </row>
 153         </tbody>
 154       </tgroup>
 155     </table>
 156
 157     <table pgwide="1" frame="none" id="modulator-txsubchans">
 158       <title>Modulator Audio Transmission Flags</title>
 159       <tgroup cols="3">
 160         &cs-def;
 161         <tbody valign="top">
 162           <row>
 163             <entry><constant>V4L2_TUNER_SUB_MONO</constant></entry>
 164             <entry>0x0001</entry>
 165             <entry>Modulate channel 1 as mono audio, when the input
 166 has more channels, a down-mix of channel 1 and 2. This flag does not
 167 combine with <constant>V4L2_TUNER_SUB_STEREO</constant> or
 168 <constant>V4L2_TUNER_SUB_LANG1</constant>.</entry>
 169           </row>
 170           <row>
 171             <entry><constant>V4L2_TUNER_SUB_STEREO</constant></entry>
 172             <entry>0x0002</entry>
 173             <entry>Modulate channel 1 and 2 as left and right
 174 channel of a stereo audio signal. When the input has only one channel
 175 or two channels and <constant>V4L2_TUNER_SUB_SAP</constant> is also
 176 set, channel 1 is encoded as left and right channel. This flag does
 177 not combine with <constant>V4L2_TUNER_SUB_MONO</constant> or
 178 <constant>V4L2_TUNER_SUB_LANG1</constant>. When the driver does not
 179 support stereo audio it shall fall back to mono.</entry>
 180           </row>
 181           <row>
 182             <entry><constant>V4L2_TUNER_SUB_LANG1</constant></entry>
 183             <entry>0x0008</entry>
 184             <entry>Modulate channel 1 and 2 as primary and secondary
 185 language of a bilingual audio signal. When the input has only one
 186 channel it is used for both languages. It is not possible to encode
 187 the primary or secondary language only. This flag does not combine
 188 with <constant>V4L2_TUNER_SUB_MONO</constant>,
 189 <constant>V4L2_TUNER_SUB_STEREO</constant> or
 190 <constant>V4L2_TUNER_SUB_SAP</constant>. If the hardware does not
 191 support the respective audio matrix, or the current video standard
 192 does not permit bilingual audio the
 193 <constant>VIDIOC_S_MODULATOR</constant> ioctl shall return an &EINVAL;
 194 and the driver shall fall back to mono or stereo mode.</entry>
 195           </row>
 196           <row>
 197             <entry><constant>V4L2_TUNER_SUB_LANG2</constant></entry>
 198             <entry>0x0004</entry>
 199             <entry>Same effect as
 200 <constant>V4L2_TUNER_SUB_SAP</constant>.</entry>
 201           </row>
 202           <row>
 203             <entry><constant>V4L2_TUNER_SUB_SAP</constant></entry>
 204             <entry>0x0004</entry>
 205             <entry>When combined with <constant>V4L2_TUNER_SUB_MONO
 206 </constant> the first channel is encoded as mono audio, the last
 207 channel as Second Audio Program. When the input has only one channel
 208 it is used for both audio tracks. When the input has three channels
 209 the mono track is a down-mix of channel 1 and 2. When combined with
 210 <constant>V4L2_TUNER_SUB_STEREO</constant> channel 1 and 2 are
 211 encoded as left and right stereo audio, channel 3 as Second Audio
 212 Program. When the input has only two channels, the first is encoded as
 213 left and right channel and the second as SAP. When the input has only
 214 one channel it is used for all audio tracks. It is not possible to
 215 encode a Second Audio Program only. This flag must combine with
 216 <constant>V4L2_TUNER_SUB_MONO</constant> or
 217 <constant>V4L2_TUNER_SUB_STEREO</constant>. If the hardware does not
 218 support the respective audio matrix, or the current video standard
 219 does not permit SAP the <constant>VIDIOC_S_MODULATOR</constant> ioctl
 220 shall return an &EINVAL; and driver shall fall back to mono or stereo
 221 mode.</entry>
 222           </row>
 223           <row>
 224             <entry><constant>V4L2_TUNER_SUB_RDS</constant></entry>
 225             <entry>0x0010</entry>
 226             <entry>Enable the RDS encoder for a radio FM transmitter.</entry>
 227           </row>
 228         </tbody>
 229       </tgroup>
 230     </table>
 231   </refsect1>
 232
 233   <refsect1>
 234     &return-value;
 235
 236     <variablelist>
 237       <varlistentry>
 238         <term><errorcode>EINVAL</errorcode></term>
 239         <listitem>
 240           <para>The &v4l2-modulator;
 241 <structfield>index</structfield> is out of bounds.</para>
 242         </listitem>
 243       </varlistentry>
 244     </variablelist>
 245   </refsect1>
 246 </refentry>