metadata in radio waves?

[JeenLeen]

Thinking of things like car radios.

In my newer vehicle, the radio station sometimes shows the name of the song and artist. Can someone explain how it knows? I have assumed that radio technology (in the sense of FM/AM radio, or FM more specifically) is basically the same as it was decades ago, in the sense of using frequencies to make a 'station' and such, so how does metadata about song titles travel alongside music?

Also, one station in my area seems to have an odd time-lag. When I switch to it, the song plays a few seconds, then 'jumps back' to where it started. But if the waves are moving "in real time"... it just seems odd that it's possible for a lag like that.
I'd think it's my radio, but it only happens with one station (and it seems to have been fixed in the last couple weeks.)

OR is it just that it's still the same sort of radio frequency, but transmission and reception tech has improved so that metadata can be sent at the 'same time' as the actual 'wave info' that gets translated into the music I hear?

[Manga Shoggoth]

They would not be able to do that with a traditional AM/FM signal where the sound is directly modulated into the signal.

However, if you are listening to a digital radio channel, then yes, they can send the metadata along with the music. The bits themselves are being transmitted using AM or FM, and after that it is the interpretation of data in the device. A simple title string (aka a few bytes of text) would be small enough to transmit frequently in the body of the signal.

Edit: As to the lag, well it's possible that the radio is caching data; or there may be two transmitters and it is switching from one to the other (and there is a lag between them).

[Yora]

Oh, that's what digital radio is. Haven't really used on in ages.

[factotum]

They would not be able to do that with a traditional AM/FM signal where the sound is directly modulated into the signal.

Actually, they totally *can* do that--what we're talking about here is the Radio Data System, which is a method for embedding small amounts of digital information into an otherwise entirely conventional FM radio signal. More info:

https://en.wikipedia.org/wiki/Radio_Data_System

[Khedrac]

Oh, that's what digital radio is. Haven't really used on in ages.

Actually not really. Digital radio is (in the UK) sold as a better listening experience because the signal is less subject to distortion and thus you get a better sound and they can carry both more information and they can transmit more channels.

In practice it uses a much short-ranged part of the spectum (hence they want people to switch to they can reuse the am/fm channels for other purposes) and despite claims that it canot be done, an am digital radio was unveiled quite a few years ago.
Also the "all (good) or nothing" claim about digital radio is also wrong - I have a walkman-style digital radio somewhere and as a general rule the signal was pretty terrible and the sound often lousy with interference (something that "cannot happen" - ha!).

If you have a digital radio you don't plan to move you should be able to adjust it to get great sound quality, but moving around will show you just how patchy the signal really is. It is a lot better than it used to be (which is why people have accepted cars switching to digital radios) but I still regularly drive through places where the car radio switches to FM and then back again to maintain the signal.

The main selling point is that the choice of stations is far greater than with analogue - but how many people regularly listen to more than 2 or 3 stations (if that)? It's a classic "this product is great because it has a feaure you don't need and won't use" sales pitch. Esecially now when most people can lsiten over the internet where there is an even bigger range of stations.

All radio is signal modulation of some form - digital radio just uses data compression techniques to get a lot more information into a small frequency range and starts with a digital signal to enable it to do so.

[Radar]

There are even more interesting you can do with metadata in the radio signal. We got a newer car recently and were pretty surprised that the CD music would automatically switch to radio for traffic information and switch back afterwards. A pretty cool feature to be honest.

[Yora]

I've seen that too. (And then had to figure out how to turn it off.)

Now that I think about it, many programmable radios back in the 90s could at the very least tell you the name of the station you had selected. I doubt those were pre-programmed into the radios, so it would have to be transmitted with the radio signal somehow. Transmitting only three to eight letters should be so tiny you wouldn't be able to notice any gaps in the music (or even the vibrations in the speakers reacting to it).

[snowblizz]

I doubt those were pre-programmed into the radios, so it would have to be transmitted with the radio signal somehow.
Really old radios came with printed on names of the stations. Because neither stations nor frequencies really changed.

[Batcathat]

There are even more interesting you can do with metadata in the radio signal. We got a newer car recently and were pretty surprised that the CD music would automatically switch to radio for traffic information and switch back afterwards. A pretty cool feature to be honest.

I don't think that's a new feature, at least not in Sweden where I live. My car was made in 2012 and does that. My old car was made in 2003 and I'm pretty sure it did it too. But yeah, it's pretty nifty (though at least in my experience, it can be a little off-synch, so it cuts to the trafic information too early or too late).

[Manga Shoggoth]

Actually, they totally *can* do that--what we're talking about here is the Radio Data System, which is a method for embedding small amounts of digital information into an otherwise entirely conventional FM radio signal. More info:

https://en.wikipedia.org/wiki/Radio_Data_System

Oooh, ta! That's certianly true for FM then, but I don't think it would work for AM.