Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.
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><link linkend="sdr">SDR</link> specific modulator types are 82 <constant>V4L2_TUNER_SDR</constant> and <constant>V4L2_TUNER_RF</constant>. 83 For SDR devices <structfield>txsubchans</structfield> field must be 84 initialized to zero. 85 The term 'modulator' means SDR transmitter in this context.</para> 86 87 <para>To change the radio frequency the &VIDIOC-S-FREQUENCY; ioctl 88 is available.</para> 89 90 <table pgwide="1" frame="none" id="v4l2-modulator"> 91 <title>struct <structname>v4l2_modulator</structname></title> 92 <tgroup cols="3"> 93 &cs-str; 94 <tbody valign="top"> 95 <row> 96 <entry>__u32</entry> 97 <entry><structfield>index</structfield></entry> 98 <entry>Identifies the modulator, set by the 99 application.</entry> 100 </row> 101 <row> 102 <entry>__u8</entry> 103 <entry><structfield>name</structfield>[32]</entry> 104 <entry>Name of the modulator, a NUL-terminated ASCII 105 string. This information is intended for the user.</entry> 106 </row> 107 <row> 108 <entry>__u32</entry> 109 <entry><structfield>capability</structfield></entry> 110 <entry>Modulator capability flags. No flags are defined 111 for this field, the tuner flags in &v4l2-tuner; 112 are used accordingly. The audio flags indicate the ability 113 to encode audio subprograms. They will <emphasis>not</emphasis> 114 change for example with the current video standard.</entry> 115 </row> 116 <row> 117 <entry>__u32</entry> 118 <entry><structfield>rangelow</structfield></entry> 119 <entry>The lowest tunable frequency in units of 62.5 120 KHz, or if the <structfield>capability</structfield> flag 121 <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5 122 Hz, or if the <structfield>capability</structfield> flag 123 <constant>V4L2_TUNER_CAP_1HZ</constant> is set, in units of 1 Hz.</entry> 124 </row> 125 <row> 126 <entry>__u32</entry> 127 <entry><structfield>rangehigh</structfield></entry> 128 <entry>The highest tunable frequency in units of 62.5 129 KHz, or if the <structfield>capability</structfield> flag 130 <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5 131 Hz, or if the <structfield>capability</structfield> flag 132 <constant>V4L2_TUNER_CAP_1HZ</constant> is set, in units of 1 Hz.</entry> 133 </row> 134 <row> 135 <entry>__u32</entry> 136 <entry><structfield>txsubchans</structfield></entry> 137 <entry>With this field applications can determine how 138 audio sub-carriers shall be modulated. It contains a set of flags as 139 defined in <xref linkend="modulator-txsubchans" />. Note the tuner 140 <structfield>rxsubchans</structfield> flags are reused, but the 141 semantics are different. Video output devices are assumed to have an 142 analog or PCM audio input with 1-3 channels. The 143 <structfield>txsubchans</structfield> flags select one or more 144 channels for modulation, together with some audio subprogram 145 indicator, for example a stereo pilot tone.</entry> 146 </row> 147 <row> 148 <entry>__u32</entry> 149 <entry><structfield>type</structfield></entry> 150 <entry spanname="hspan">Type of the modulator, see <xref 151 linkend="v4l2-tuner-type" />.</entry> 152 </row> 153 <row> 154 <entry>__u32</entry> 155 <entry><structfield>reserved</structfield>[3]</entry> 156 <entry>Reserved for future extensions. Drivers and 157 applications must set the array to zero.</entry> 158 </row> 159 </tbody> 160 </tgroup> 161 </table> 162 163 <table pgwide="1" frame="none" id="modulator-txsubchans"> 164 <title>Modulator Audio Transmission Flags</title> 165 <tgroup cols="3"> 166 &cs-def; 167 <tbody valign="top"> 168 <row> 169 <entry><constant>V4L2_TUNER_SUB_MONO</constant></entry> 170 <entry>0x0001</entry> 171 <entry>Modulate channel 1 as mono audio, when the input 172 has more channels, a down-mix of channel 1 and 2. This flag does not 173 combine with <constant>V4L2_TUNER_SUB_STEREO</constant> or 174 <constant>V4L2_TUNER_SUB_LANG1</constant>.</entry> 175 </row> 176 <row> 177 <entry><constant>V4L2_TUNER_SUB_STEREO</constant></entry> 178 <entry>0x0002</entry> 179 <entry>Modulate channel 1 and 2 as left and right 180 channel of a stereo audio signal. When the input has only one channel 181 or two channels and <constant>V4L2_TUNER_SUB_SAP</constant> is also 182 set, channel 1 is encoded as left and right channel. This flag does 183 not combine with <constant>V4L2_TUNER_SUB_MONO</constant> or 184 <constant>V4L2_TUNER_SUB_LANG1</constant>. When the driver does not 185 support stereo audio it shall fall back to mono.</entry> 186 </row> 187 <row> 188 <entry><constant>V4L2_TUNER_SUB_LANG1</constant></entry> 189 <entry>0x0008</entry> 190 <entry>Modulate channel 1 and 2 as primary and secondary 191 language of a bilingual audio signal. When the input has only one 192 channel it is used for both languages. It is not possible to encode 193 the primary or secondary language only. This flag does not combine 194 with <constant>V4L2_TUNER_SUB_MONO</constant>, 195 <constant>V4L2_TUNER_SUB_STEREO</constant> or 196 <constant>V4L2_TUNER_SUB_SAP</constant>. If the hardware does not 197 support the respective audio matrix, or the current video standard 198 does not permit bilingual audio the 199 <constant>VIDIOC_S_MODULATOR</constant> ioctl shall return an &EINVAL; 200 and the driver shall fall back to mono or stereo mode.</entry> 201 </row> 202 <row> 203 <entry><constant>V4L2_TUNER_SUB_LANG2</constant></entry> 204 <entry>0x0004</entry> 205 <entry>Same effect as 206 <constant>V4L2_TUNER_SUB_SAP</constant>.</entry> 207 </row> 208 <row> 209 <entry><constant>V4L2_TUNER_SUB_SAP</constant></entry> 210 <entry>0x0004</entry> 211 <entry>When combined with <constant>V4L2_TUNER_SUB_MONO 212 </constant> the first channel is encoded as mono audio, the last 213 channel as Second Audio Program. When the input has only one channel 214 it is used for both audio tracks. When the input has three channels 215 the mono track is a down-mix of channel 1 and 2. When combined with 216 <constant>V4L2_TUNER_SUB_STEREO</constant> channel 1 and 2 are 217 encoded as left and right stereo audio, channel 3 as Second Audio 218 Program. When the input has only two channels, the first is encoded as 219 left and right channel and the second as SAP. When the input has only 220 one channel it is used for all audio tracks. It is not possible to 221 encode a Second Audio Program only. This flag must combine with 222 <constant>V4L2_TUNER_SUB_MONO</constant> or 223 <constant>V4L2_TUNER_SUB_STEREO</constant>. If the hardware does not 224 support the respective audio matrix, or the current video standard 225 does not permit SAP the <constant>VIDIOC_S_MODULATOR</constant> ioctl 226 shall return an &EINVAL; and driver shall fall back to mono or stereo 227 mode.</entry> 228 </row> 229 <row> 230 <entry><constant>V4L2_TUNER_SUB_RDS</constant></entry> 231 <entry>0x0010</entry> 232 <entry>Enable the RDS encoder for a radio FM transmitter.</entry> 233 </row> 234 </tbody> 235 </tgroup> 236 </table> 237 </refsect1> 238 239 <refsect1> 240 &return-value; 241 242 <variablelist> 243 <varlistentry> 244 <term><errorcode>EINVAL</errorcode></term> 245 <listitem> 246 <para>The &v4l2-modulator; 247 <structfield>index</structfield> is out of bounds.</para> 248 </listitem> 249 </varlistentry> 250 </variablelist> 251 </refsect1> 252 </refentry>
