Some RadioText research

While developing a solution to an issue it has turned out that there are a lot of different implementations of RadioText, not all of which strictly follow the RDS standard.

Below some statistic and research about those implementations based on 455 recorded stations from around the world from walczakp/rds-spy-logs.

Group 2A vs. Group 2B

According to the standard, RadioText can be sent either in type 2A or 2B groups. 2A supports a maximum message length of 64 characters; 2B only supports 32-character messages.

In the sample data, there are:

• 2A: 122,968 groups from 308 stations
• 2B: 14 groups from 9 stations

It's pretty safe to say that in practice, RadioText is only transmitted in 2A groups.

String termination

The end of a RadioText string can be signaled with the 0x0D character. But many stations opt to pad the message up to 64 characters with blank spaces instead. Some use neither.

Out of the 308 stations that transmit RadioText,

• 94 stations make use of the end-of-string character.
• 204 stations pad their messages to 64 characters without an end character, at least once.
• Several (how many?) stations end their strings before 64 characters and use no string terminator.

Resistant to redsea

There are ~96 stations that carry 2A but where redsea is unable to decode radiotext.

Weird redsea behavior

This kind of behavior is seen on multiple stations (¶ represents end-of-string marker):

{"pi":"0x7DC9","group":"2A","radiotext":"The Breakup Song by Francesca Battistelli on Z88.3 FM¶","prog_type":"Culture","tp":true}
{"pi":"0x7DC9","group":"2A","radiotext":"The Breakup Song by Francesca Battistelli on Z88.3 F","prog_type":"Culture","tp":true}
{"pi":"0x7DC9","group":"2A","radiotext":"The Breakup Song by Francesca Battistelli on Z88.3 FM¶","prog_type":"Culture","tp":true}
{"pi":"0x7DC9","group":"2A","radiotext":"The Breakup Song by Francesca Battistelli on Z88.3 F","prog_type":"Culture","tp":true}
{"pi":"0x7DC9","group":"2A","radiotext":"The Breakup Song by Francesca Battistelli on Z88.3 FM¶","prog_type":"Culture","tp":true}