diff options
Diffstat (limited to 'Documentation/DocBook/v4l/dev-rds.xml')
| -rw-r--r-- | Documentation/DocBook/v4l/dev-rds.xml | 68 |
1 files changed, 51 insertions, 17 deletions
diff --git a/Documentation/DocBook/v4l/dev-rds.xml b/Documentation/DocBook/v4l/dev-rds.xml index 0869d701b1e5..360d2737e649 100644 --- a/Documentation/DocBook/v4l/dev-rds.xml +++ b/Documentation/DocBook/v4l/dev-rds.xml @@ -3,15 +3,16 @@ <para>The Radio Data System transmits supplementary information in binary format, for example the station name or travel information, on an inaudible audio subcarrier of a radio program. This -interface is aimed at devices capable of receiving and decoding RDS +interface is aimed at devices capable of receiving and/or transmitting RDS information.</para> <para>For more information see the core RDS standard <xref linkend="en50067" /> and the RBDS standard <xref linkend="nrsc4" />.</para> <para>Note that the RBDS standard as is used in the USA is almost identical -to the RDS standard. Any RDS decoder can also handle RBDS. Only some of the fields -have slightly different meanings. See the RBDS standard for more information.</para> +to the RDS standard. Any RDS decoder/encoder can also handle RBDS. Only some of the +fields have slightly different meanings. See the RBDS standard for more +information.</para> <para>The RBDS standard also specifies support for MMBS (Modified Mobile Search). This is a proprietary format which seems to be discontinued. The RDS interface does not @@ -21,16 +22,25 @@ be needed, then please contact the linux-media mailing list: &v4l-ml;.</para> <section> <title>Querying Capabilities</title> - <para>Devices supporting the RDS capturing API -set the <constant>V4L2_CAP_RDS_CAPTURE</constant> flag in + <para>Devices supporting the RDS capturing API set +the <constant>V4L2_CAP_RDS_CAPTURE</constant> flag in the <structfield>capabilities</structfield> field of &v4l2-capability; -returned by the &VIDIOC-QUERYCAP; ioctl. -Any tuner that supports RDS will set the -<constant>V4L2_TUNER_CAP_RDS</constant> flag in the <structfield>capability</structfield> -field of &v4l2-tuner;. -Whether an RDS signal is present can be detected by looking at -the <structfield>rxsubchans</structfield> field of &v4l2-tuner;: the -<constant>V4L2_TUNER_SUB_RDS</constant> will be set if RDS data was detected.</para> +returned by the &VIDIOC-QUERYCAP; ioctl. Any tuner that supports RDS +will set the <constant>V4L2_TUNER_CAP_RDS</constant> flag in +the <structfield>capability</structfield> field of &v4l2-tuner;. If +the driver only passes RDS blocks without interpreting the data +the <constant>V4L2_TUNER_SUB_RDS_BLOCK_IO</constant> flag has to be +set, see <link linkend="reading-rds-data">Reading RDS data</link>. +For future use the +flag <constant>V4L2_TUNER_SUB_RDS_CONTROLS</constant> has also been +defined. However, a driver for a radio tuner with this capability does +not yet exist, so if you are planning to write such a driver you +should discuss this on the linux-media mailing list: &v4l-ml;.</para> + + <para> Whether an RDS signal is present can be detected by looking +at the <structfield>rxsubchans</structfield> field of &v4l2-tuner;: +the <constant>V4L2_TUNER_SUB_RDS</constant> will be set if RDS data +was detected.</para> <para>Devices supporting the RDS output API set the <constant>V4L2_CAP_RDS_OUTPUT</constant> flag in @@ -40,16 +50,31 @@ Any modulator that supports RDS will set the <constant>V4L2_TUNER_CAP_RDS</constant> flag in the <structfield>capability</structfield> field of &v4l2-modulator;. In order to enable the RDS transmission one must set the <constant>V4L2_TUNER_SUB_RDS</constant> -bit in the <structfield>txsubchans</structfield> field of &v4l2-modulator;.</para> - +bit in the <structfield>txsubchans</structfield> field of &v4l2-modulator;. +If the driver only passes RDS blocks without interpreting the data +the <constant>V4L2_TUNER_SUB_RDS_BLOCK_IO</constant> flag has to be set. If the +tuner is capable of handling RDS entities like program identification codes and radio +text, the flag <constant>V4L2_TUNER_SUB_RDS_CONTROLS</constant> should be set, +see <link linkend="writing-rds-data">Writing RDS data</link> and +<link linkend="fm-tx-controls">FM Transmitter Control Reference</link>.</para> </section> - <section> + <section id="reading-rds-data"> <title>Reading RDS data</title> <para>RDS data can be read from the radio device -with the &func-read; function. The data is packed in groups of three bytes, +with the &func-read; function. The data is packed in groups of three bytes.</para> + </section> + + <section id="writing-rds-data"> + <title>Writing RDS data</title> + + <para>RDS data can be written to the radio device +with the &func-write; function. The data is packed in groups of three bytes, as follows:</para> + </section> + + <section> <table frame="none" pgwide="1" id="v4l2-rds-data"> <title>struct <structname>v4l2_rds_data</structname></title> @@ -111,48 +136,57 @@ as follows:</para> <tbody valign="top"> <row> <entry>V4L2_RDS_BLOCK_MSK</entry> + <entry> </entry> <entry>7</entry> <entry>Mask for bits 0-2 to get the block ID.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_A</entry> + <entry> </entry> <entry>0</entry> <entry>Block A.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_B</entry> + <entry> </entry> <entry>1</entry> <entry>Block B.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_C</entry> + <entry> </entry> <entry>2</entry> <entry>Block C.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_D</entry> + <entry> </entry> <entry>3</entry> <entry>Block D.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_C_ALT</entry> + <entry> </entry> <entry>4</entry> <entry>Block C'.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_INVALID</entry> + <entry>read-only</entry> <entry>7</entry> <entry>An invalid block.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_CORRECTED</entry> + <entry>read-only</entry> <entry>0x40</entry> <entry>A bit error was detected but corrected.</entry> </row> <row> <entry>V4L2_RDS_BLOCK_ERROR</entry> + <entry>read-only</entry> <entry>0x80</entry> - <entry>An incorrectable error occurred.</entry> + <entry>An uncorrectable error occurred.</entry> </row> </tbody> </tgroup> |