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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
240<!--
241Local Variables:
242mode: sgml
243sgml-parent-document: "v4l2.sgml"
244indent-tabs-mode: nil
245End:
246-->
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