The Radio Data System transmits supplementary information in binary format, for example the station name or travel information, on a inaudible audio subcarrier of a radio program. This interface aims at devices capable of receiving and decoding RDS information.
The V4L API defines its RDS API as follows.
From radio devices supporting it, RDS data can be read
with the read() function. The data is packed in groups of three,
as follows:
First Octet Least Significant Byte of RDS Block
Second Octet Most Significant Byte of RDS Block
Third Octet Bit 7: Error bit. Indicates that an uncorrectable error occurred during reception of this block. Bit 6: Corrected bit. Indicates that an error was corrected for this data block. Bits 5-3: Received Offset. Indicates the offset received by the sync system. Bits 2-0: Offset Name. Indicates the offset applied to this data.
It was argued the RDS API should be
extended before integration into V4L2, no new API has been devised yet.
Please write to the Video4Linux mailing list for discussion: https://listman.redhat.com/mailman/listinfo/video4linux-list.
Meanwhile no V4L2 driver should set the
V4L2_CAP_RDS_CAPTURE capability flag.