From 8e4bff4cab0ddac6060645b0715210484d02ff40 Mon Sep 17 00:00:00 2001 From: Yuval Adam <_@yuv.al> Date: Wed, 30 Aug 2017 08:25:59 +0000 Subject: Initial file dump from open source release --- Documentation/DocBook/media/v4l/dev-rds.xml | 196 ++++++++++++++++++++++++++++ 1 file changed, 196 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/dev-rds.xml (limited to 'Documentation/DocBook/media/v4l/dev-rds.xml') diff --git a/Documentation/DocBook/media/v4l/dev-rds.xml b/Documentation/DocBook/media/v4l/dev-rds.xml new file mode 100644 index 00000000..be2f3373 --- /dev/null +++ b/Documentation/DocBook/media/v4l/dev-rds.xml @@ -0,0 +1,196 @@ + RDS Interface + + 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/or transmitting RDS +information. + + For more information see the core RDS standard +and the RBDS standard . + + Note that the RBDS standard as is used in the USA is almost identical +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. + + 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 +support this format. Should support for MMBS (or the so-called 'E blocks' in general) +be needed, then please contact the linux-media mailing list: &v4l-ml;. + +
+ Querying Capabilities + + Devices supporting the RDS capturing API set +the V4L2_CAP_RDS_CAPTURE flag in +the capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. Any tuner that supports RDS +will set the V4L2_TUNER_CAP_RDS flag in +the capability field of &v4l2-tuner;. If +the driver only passes RDS blocks without interpreting the data +the V4L2_TUNER_CAP_RDS_BLOCK_IO flag has to be +set, see Reading RDS data. +For future use the +flag V4L2_TUNER_CAP_RDS_CONTROLS 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;. + + Whether an RDS signal is present can be detected by looking +at the rxsubchans field of &v4l2-tuner;: +the V4L2_TUNER_SUB_RDS will be set if RDS data +was detected. + + Devices supporting the RDS output API +set the V4L2_CAP_RDS_OUTPUT flag in +the capabilities field of &v4l2-capability; +returned by the &VIDIOC-QUERYCAP; ioctl. +Any modulator that supports RDS will set the +V4L2_TUNER_CAP_RDS flag in the capability +field of &v4l2-modulator;. +In order to enable the RDS transmission one must set the V4L2_TUNER_SUB_RDS +bit in the txsubchans field of &v4l2-modulator;. +If the driver only passes RDS blocks without interpreting the data +the V4L2_TUNER_CAP_RDS_BLOCK_IO flag has to be set. If the +tuner is capable of handling RDS entities like program identification codes and radio +text, the flag V4L2_TUNER_CAP_RDS_CONTROLS should be set, +see Writing RDS data and +FM Transmitter Control Reference. +
+ +
+ Reading RDS data + + RDS data can be read from the radio device +with the &func-read; function. The data is packed in groups of three bytes. +
+ +
+ Writing RDS data + + 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: +
+ +
+ RDS datastructures + + struct +<structname>v4l2_rds_data</structname> + + + + + + + __u8 + lsb + Least Significant Byte of RDS Block + + + __u8 + msb + Most Significant Byte of RDS Block + + + __u8 + block + Block description + + + +
+ + Block description + + + + + + Bits 0-2 + Block (aka offset) of the received data. + + + Bits 3-5 + Deprecated. Currently identical to bits 0-2. Do not use these bits. + + + Bit 6 + Corrected bit. Indicates that an error was corrected for this data block. + + + Bit 7 + Error bit. Indicates that an uncorrectable error occurred during reception of this block. + + + +
+ + + Block defines + + + + + + + + V4L2_RDS_BLOCK_MSK + + 7 + Mask for bits 0-2 to get the block ID. + + + V4L2_RDS_BLOCK_A + + 0 + Block A. + + + V4L2_RDS_BLOCK_B + + 1 + Block B. + + + V4L2_RDS_BLOCK_C + + 2 + Block C. + + + V4L2_RDS_BLOCK_D + + 3 + Block D. + + + V4L2_RDS_BLOCK_C_ALT + + 4 + Block C'. + + + V4L2_RDS_BLOCK_INVALID + read-only + 7 + An invalid block. + + + V4L2_RDS_BLOCK_CORRECTED + read-only + 0x40 + A bit error was detected but corrected. + + + V4L2_RDS_BLOCK_ERROR + read-only + 0x80 + An uncorrectable error occurred. + + + +
+
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