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Based on kernel version 3.13. Page generated on 2014-01-20 22:02 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>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.</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
122	KHz, or if the <structfield>capability</structfield> flag
123	<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
124	Hz.</entry>
125		  </row>
126		  <row>
127		    <entry>__u32</entry>
128		    <entry><structfield>txsubchans</structfield></entry>
129		    <entry>With this field applications can determine how
130	audio sub-carriers shall be modulated. It contains a set of flags as
131	defined in <xref linkend="modulator-txsubchans" />. Note the tuner
132	<structfield>rxsubchans</structfield> flags are reused, but the
133	semantics are different. Video output devices are assumed to have an
134	analog or PCM audio input with 1-3 channels. The
135	<structfield>txsubchans</structfield> flags select one or more
136	channels for modulation, together with some audio subprogram
137	indicator, 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
143	applications 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
158	has more channels, a down-mix of channel 1 and 2. This flag does not
159	combine 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
166	channel of a stereo audio signal. When the input has only one channel
167	or two channels and <constant>V4L2_TUNER_SUB_SAP</constant> is also
168	set, channel 1 is encoded as left and right channel. This flag does
169	not combine with <constant>V4L2_TUNER_SUB_MONO</constant> or
170	<constant>V4L2_TUNER_SUB_LANG1</constant>. When the driver does not
171	support 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
177	language of a bilingual audio signal. When the input has only one
178	channel it is used for both languages. It is not possible to encode
179	the primary or secondary language only. This flag does not combine
180	with <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
183	support the respective audio matrix, or the current video standard
184	does not permit bilingual audio the
185	<constant>VIDIOC_S_MODULATOR</constant> ioctl shall return an &EINVAL;
186	and 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
199	channel as Second Audio Program. When the input has only one channel
200	it is used for both audio tracks. When the input has three channels
201	the 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
203	encoded as left and right stereo audio, channel 3 as Second Audio
204	Program. When the input has only two channels, the first is encoded as
205	left and right channel and the second as SAP. When the input has only
206	one channel it is used for all audio tracks. It is not possible to
207	encode 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
210	support the respective audio matrix, or the current video standard
211	does not permit SAP the <constant>VIDIOC_S_MODULATOR</constant> ioctl
212	shall return an &EINVAL; and driver shall fall back to mono or stereo
213	mode.</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>
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