About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

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




Custom Search

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>
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.