Radio World checked
back in with WREK(FM) in Atlanta
about a customized use of RDS on which we reported earlier.
We told you last
month that the station at the Georgia Institute of Technology had “hacked” its
RDS stream to provide additional dynamic text over receiver displays tuned to
its analog and HD Radio signals, as well as on its Internet stream.
The project involved
the station’s Broadcast Electronics AudioVault system with RDDI software
engine, configured to pull source text strings from a remote machine. Chris
Campbell, the former station engineer, wrote custom software that references a
script and delivers the text on a schedule defined by timecode markers. (He
describes the setup in more detail here.)
provides an update:
“We did indeed have
the final event that Wednesday night,” he writes.
“The analog/RDS and
HD feeds have been working well. For Internet streaming, iTunes has worked for
most listeners, although it alternates between showing the PS and RT text
strings, instead of just displaying RT, which has been a bit annoying for our
“One critical factor
we’ve discovered in doing this is that there is quite a bit of differential lag
on the various outputs — they don’t all come out at the same time. And of
course different receivers have different display behavior characteristics.
“So it makes for a
bit of a balancing act when trying to sync the audio and text. We have not yet
implemented any kind of differential delay, although I suspect that the RDDI
engine offers that.”
reference to Alan Jurison’s series about
RDS for Radio World.
“In it he described
some of the loading issues of RDS (i.e., how fast can you push text). For our
system, I have found that a good rule of thumb for timing is 1.6 characters per
second, so for example if you want to push out 32 characters, you need to then
wait 20 seconds for those characters to transmit completely. I also settled on
text strings no longer than 64 characters; I don’t think there’s a limit in RDS
protocol, but I found that some receivers, and Internet streaming players, tended
to cut off around there. So I just kept it below 64 characters to be safe.”
Tell us about your
experiences with RDS. Write to firstname.lastname@example.org.