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 63the <structfield>index</structfield> field and zero out the 64<structfield>reserved</structfield> array of a &v4l2-modulator; and 65call the <constant>VIDIOC_G_MODULATOR</constant> ioctl with a pointer 66to 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 68applications shall begin at index zero, incrementing by one until the 69driver returns <errorcode>EINVAL</errorcode>.</para> 70 71 <para>Modulators have two writable properties, an audio 72modulation set and the radio frequency. To change the modulated audio 73subprograms, 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 77different audio modulation if the request cannot be satisfied. However 78this is a write-only ioctl, it does not return the actual audio 79modulation selected.</para> 80 81 <para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl 82is 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 93application.</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 99string. 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 105for this field, the tuner flags in &v4l2-tuner; 106are used accordingly. The audio flags indicate the ability 107to encode audio subprograms. They will <emphasis>not</emphasis> 108change 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 114KHz, or if the <structfield>capability</structfield> flag 115<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5 116Hz.</entry> 117 </row> 118 <row> 119 <entry>__u32</entry> 120 <entry><structfield>rangehigh</structfield></entry> 121 <entry>The highest tunable frequency in units of 62.5 122KHz, or if the <structfield>capability</structfield> flag 123<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5 124Hz.</entry> 125 </row> 126 <row> 127 <entry>__u32</entry> 128 <entry><structfield>txsubchans</structfield></entry> 129 <entry>With this field applications can determine how 130audio sub-carriers shall be modulated. It contains a set of flags as 131defined in <xref linkend="modulator-txsubchans" />. Note the tuner 132<structfield>rxsubchans</structfield> flags are reused, but the 133semantics are different. Video output devices are assumed to have an 134analog or PCM audio input with 1-3 channels. The 135<structfield>txsubchans</structfield> flags select one or more 136channels for modulation, together with some audio subprogram 137indicator, for example a stereo pilot tone.</entry> 138 </row> 139 <row> 140 <entry>__u32</entry> 141 <entry><structfield>reserved</structfield>[4]</entry> 142 <entry>Reserved for future extensions. Drivers and 143applications must set the array to zero.</entry> 144 </row> 145 </tbody> 146 </tgroup> 147 </table> 148 149 <table pgwide="1" frame="none" id="modulator-txsubchans"> 150 <title>Modulator Audio Transmission Flags</title> 151 <tgroup cols="3"> 152 &cs-def; 153 <tbody valign="top"> 154 <row> 155 <entry><constant>V4L2_TUNER_SUB_MONO</constant></entry> 156 <entry>0x0001</entry> 157 <entry>Modulate channel 1 as mono audio, when the input 158has more channels, a down-mix of channel 1 and 2. This flag does not 159combine with <constant>V4L2_TUNER_SUB_STEREO</constant> or 160<constant>V4L2_TUNER_SUB_LANG1</constant>.</entry> 161 </row> 162 <row> 163 <entry><constant>V4L2_TUNER_SUB_STEREO</constant></entry> 164 <entry>0x0002</entry> 165 <entry>Modulate channel 1 and 2 as left and right 166channel of a stereo audio signal. When the input has only one channel 167or two channels and <constant>V4L2_TUNER_SUB_SAP</constant> is also 168set, channel 1 is encoded as left and right channel. This flag does 169not combine with <constant>V4L2_TUNER_SUB_MONO</constant> or 170<constant>V4L2_TUNER_SUB_LANG1</constant>. When the driver does not 171support stereo audio it shall fall back to mono.</entry> 172 </row> 173 <row> 174 <entry><constant>V4L2_TUNER_SUB_LANG1</constant></entry> 175 <entry>0x0008</entry> 176 <entry>Modulate channel 1 and 2 as primary and secondary 177language of a bilingual audio signal. When the input has only one 178channel it is used for both languages. It is not possible to encode 179the primary or secondary language only. This flag does not combine 180with <constant>V4L2_TUNER_SUB_MONO</constant>, 181<constant>V4L2_TUNER_SUB_STEREO</constant> or 182<constant>V4L2_TUNER_SUB_SAP</constant>. If the hardware does not 183support the respective audio matrix, or the current video standard 184does not permit bilingual audio the 185<constant>VIDIOC_S_MODULATOR</constant> ioctl shall return an &EINVAL; 186and the driver shall fall back to mono or stereo mode.</entry> 187 </row> 188 <row> 189 <entry><constant>V4L2_TUNER_SUB_LANG2</constant></entry> 190 <entry>0x0004</entry> 191 <entry>Same effect as 192<constant>V4L2_TUNER_SUB_SAP</constant>.</entry> 193 </row> 194 <row> 195 <entry><constant>V4L2_TUNER_SUB_SAP</constant></entry> 196 <entry>0x0004</entry> 197 <entry>When combined with <constant>V4L2_TUNER_SUB_MONO 198</constant> the first channel is encoded as mono audio, the last 199channel as Second Audio Program. When the input has only one channel 200it is used for both audio tracks. When the input has three channels 201the mono track is a down-mix of channel 1 and 2. When combined with 202<constant>V4L2_TUNER_SUB_STEREO</constant> channel 1 and 2 are 203encoded as left and right stereo audio, channel 3 as Second Audio 204Program. When the input has only two channels, the first is encoded as 205left and right channel and the second as SAP. When the input has only 206one channel it is used for all audio tracks. It is not possible to 207encode a Second Audio Program only. This flag must combine with 208<constant>V4L2_TUNER_SUB_MONO</constant> or 209<constant>V4L2_TUNER_SUB_STEREO</constant>. If the hardware does not 210support the respective audio matrix, or the current video standard 211does not permit SAP the <constant>VIDIOC_S_MODULATOR</constant> ioctl 212shall return an &EINVAL; and driver shall fall back to mono or stereo 213mode.</entry> 214 </row> 215 <row> 216 <entry><constant>V4L2_TUNER_SUB_RDS</constant></entry> 217 <entry>0x0010</entry> 218 <entry>Enable the RDS encoder for a radio FM transmitter.</entry> 219 </row> 220 </tbody> 221 </tgroup> 222 </table> 223 </refsect1> 224 225 <refsect1> 226 &return-value; 227 228 <variablelist> 229 <varlistentry> 230 <term><errorcode>EINVAL</errorcode></term> 231 <listitem> 232 <para>The &v4l2-modulator; 233<structfield>index</structfield> is out of bounds.</para> 234 </listitem> 235 </varlistentry> 236 </variablelist> 237 </refsect1> 238</refentry> 239