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authorMauro Carvalho Chehab <mchehab@redhat.com>2011-05-31 15:27:44 -0400
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-07-27 16:52:05 -0400
commit4266129964b8238526936d723de65b419d8069c6 (patch)
tree38c6b5cd3dc99b8599391ffad3b87e399bef56a2 /Documentation/DocBook/media/v4l/dev-rds.xml
parent04893043ae9ea8aa82b712491ed25ba6c4ffbca3 (diff)
[media] DocBook: Move all media docbook stuff into its own directory
This patch addresses several issues pointed by Randy Dunlap <rdunlap@xenotime.net> at changeset ece722c: - In the generated index.html file, "media" is listed first, but it should be listed in alphabetical order, not first. - The generated files are (hidden) in .tmpmedia/ - The link from the top-level index.html file to "media" is to media/index.html, but the file is actually in .tmpmedia/media/index.html - Please build docs with and without using "O=builddir" and test that. - Would it be possible for media to have its own Makefile instead of merging into this one? Due to the way cleandocs target works, I had to rename the media DocBook to media_api, otherwise cleandocs would remove the /media directory. Thanks-to: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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1 <title>RDS Interface</title>
2
3 <para>The Radio Data System transmits supplementary
4information in binary format, for example the station name or travel
5information, on an inaudible audio subcarrier of a radio program. This
6interface is aimed at devices capable of receiving and/or transmitting RDS
7information.</para>
8
9 <para>For more information see the core RDS standard <xref linkend="en50067" />
10and the RBDS standard <xref linkend="nrsc4" />.</para>
11
12 <para>Note that the RBDS standard as is used in the USA is almost identical
13to the RDS standard. Any RDS decoder/encoder can also handle RBDS. Only some of the
14fields have slightly different meanings. See the RBDS standard for more
15information.</para>
16
17 <para>The RBDS standard also specifies support for MMBS (Modified Mobile Search).
18This is a proprietary format which seems to be discontinued. The RDS interface does not
19support this format. Should support for MMBS (or the so-called 'E blocks' in general)
20be needed, then please contact the linux-media mailing list: &v4l-ml;.</para>
21
22 <section>
23 <title>Querying Capabilities</title>
24
25 <para>Devices supporting the RDS capturing API set
26the <constant>V4L2_CAP_RDS_CAPTURE</constant> flag in
27the <structfield>capabilities</structfield> field of &v4l2-capability;
28returned by the &VIDIOC-QUERYCAP; ioctl. Any tuner that supports RDS
29will set the <constant>V4L2_TUNER_CAP_RDS</constant> flag in
30the <structfield>capability</structfield> field of &v4l2-tuner;. If
31the driver only passes RDS blocks without interpreting the data
32the <constant>V4L2_TUNER_SUB_RDS_BLOCK_IO</constant> flag has to be
33set, see <link linkend="reading-rds-data">Reading RDS data</link>.
34For future use the
35flag <constant>V4L2_TUNER_SUB_RDS_CONTROLS</constant> has also been
36defined. However, a driver for a radio tuner with this capability does
37not yet exist, so if you are planning to write such a driver you
38should discuss this on the linux-media mailing list: &v4l-ml;.</para>
39
40 <para> Whether an RDS signal is present can be detected by looking
41at the <structfield>rxsubchans</structfield> field of &v4l2-tuner;:
42the <constant>V4L2_TUNER_SUB_RDS</constant> will be set if RDS data
43was detected.</para>
44
45 <para>Devices supporting the RDS output API
46set the <constant>V4L2_CAP_RDS_OUTPUT</constant> flag in
47the <structfield>capabilities</structfield> field of &v4l2-capability;
48returned by the &VIDIOC-QUERYCAP; ioctl.
49Any modulator that supports RDS will set the
50<constant>V4L2_TUNER_CAP_RDS</constant> flag in the <structfield>capability</structfield>
51field of &v4l2-modulator;.
52In order to enable the RDS transmission one must set the <constant>V4L2_TUNER_SUB_RDS</constant>
53bit in the <structfield>txsubchans</structfield> field of &v4l2-modulator;.
54If the driver only passes RDS blocks without interpreting the data
55the <constant>V4L2_TUNER_SUB_RDS_BLOCK_IO</constant> flag has to be set. If the
56tuner is capable of handling RDS entities like program identification codes and radio
57text, the flag <constant>V4L2_TUNER_SUB_RDS_CONTROLS</constant> should be set,
58see <link linkend="writing-rds-data">Writing RDS data</link> and
59<link linkend="fm-tx-controls">FM Transmitter Control Reference</link>.</para>
60 </section>
61
62 <section id="reading-rds-data">
63 <title>Reading RDS data</title>
64
65 <para>RDS data can be read from the radio device
66with the &func-read; function. The data is packed in groups of three bytes.</para>
67 </section>
68
69 <section id="writing-rds-data">
70 <title>Writing RDS data</title>
71
72 <para>RDS data can be written to the radio device
73with the &func-write; function. The data is packed in groups of three bytes,
74as follows:</para>
75 </section>
76
77 <section>
78 <title>RDS datastructures</title>
79 <table frame="none" pgwide="1" id="v4l2-rds-data">
80 <title>struct
81<structname>v4l2_rds_data</structname></title>
82 <tgroup cols="3">
83 <colspec colname="c1" colwidth="1*" />
84 <colspec colname="c2" colwidth="1*" />
85 <colspec colname="c3" colwidth="5*" />
86 <tbody valign="top">
87 <row>
88 <entry>__u8</entry>
89 <entry><structfield>lsb</structfield></entry>
90 <entry>Least Significant Byte of RDS Block</entry>
91 </row>
92 <row>
93 <entry>__u8</entry>
94 <entry><structfield>msb</structfield></entry>
95 <entry>Most Significant Byte of RDS Block</entry>
96 </row>
97 <row>
98 <entry>__u8</entry>
99 <entry><structfield>block</structfield></entry>
100 <entry>Block description</entry>
101 </row>
102 </tbody>
103 </tgroup>
104 </table>
105 <table frame="none" pgwide="1" id="v4l2-rds-block">
106 <title>Block description</title>
107 <tgroup cols="2">
108 <colspec colname="c1" colwidth="1*" />
109 <colspec colname="c2" colwidth="5*" />
110 <tbody valign="top">
111 <row>
112 <entry>Bits 0-2</entry>
113 <entry>Block (aka offset) of the received data.</entry>
114 </row>
115 <row>
116 <entry>Bits 3-5</entry>
117 <entry>Deprecated. Currently identical to bits 0-2. Do not use these bits.</entry>
118 </row>
119 <row>
120 <entry>Bit 6</entry>
121 <entry>Corrected bit. Indicates that an error was corrected for this data block.</entry>
122 </row>
123 <row>
124 <entry>Bit 7</entry>
125 <entry>Error bit. Indicates that an uncorrectable error occurred during reception of this block.</entry>
126 </row>
127 </tbody>
128 </tgroup>
129 </table>
130
131 <table frame="none" pgwide="1" id="v4l2-rds-block-codes">
132 <title>Block defines</title>
133 <tgroup cols="4">
134 <colspec colname="c1" colwidth="1*" />
135 <colspec colname="c2" colwidth="1*" />
136 <colspec colname="c3" colwidth="1*" />
137 <colspec colname="c4" colwidth="5*" />
138 <tbody valign="top">
139 <row>
140 <entry>V4L2_RDS_BLOCK_MSK</entry>
141 <entry> </entry>
142 <entry>7</entry>
143 <entry>Mask for bits 0-2 to get the block ID.</entry>
144 </row>
145 <row>
146 <entry>V4L2_RDS_BLOCK_A</entry>
147 <entry> </entry>
148 <entry>0</entry>
149 <entry>Block A.</entry>
150 </row>
151 <row>
152 <entry>V4L2_RDS_BLOCK_B</entry>
153 <entry> </entry>
154 <entry>1</entry>
155 <entry>Block B.</entry>
156 </row>
157 <row>
158 <entry>V4L2_RDS_BLOCK_C</entry>
159 <entry> </entry>
160 <entry>2</entry>
161 <entry>Block C.</entry>
162 </row>
163 <row>
164 <entry>V4L2_RDS_BLOCK_D</entry>
165 <entry> </entry>
166 <entry>3</entry>
167 <entry>Block D.</entry>
168 </row>
169 <row>
170 <entry>V4L2_RDS_BLOCK_C_ALT</entry>
171 <entry> </entry>
172 <entry>4</entry>
173 <entry>Block C'.</entry>
174 </row>
175 <row>
176 <entry>V4L2_RDS_BLOCK_INVALID</entry>
177 <entry>read-only</entry>
178 <entry>7</entry>
179 <entry>An invalid block.</entry>
180 </row>
181 <row>
182 <entry>V4L2_RDS_BLOCK_CORRECTED</entry>
183 <entry>read-only</entry>
184 <entry>0x40</entry>
185 <entry>A bit error was detected but corrected.</entry>
186 </row>
187 <row>
188 <entry>V4L2_RDS_BLOCK_ERROR</entry>
189 <entry>read-only</entry>
190 <entry>0x80</entry>
191 <entry>An uncorrectable error occurred.</entry>
192 </row>
193 </tbody>
194 </tgroup>
195 </table>
196 </section>
197
198<!--
199Local Variables:
200mode: sgml
201sgml-parent-document: "v4l2.sgml"
202indent-tabs-mode: nil
203End:
204 -->
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-19 05:27:53 -0500