Internet radio transmission anomaly

[Kirbstone]

I would like to bend those superior brains who regularly post here, seeking an explanation to an anomaly recently discovered at my domestic Wi-Fi outlet at home.
We are both BBC Radio 4 addicts and traditionally have recieved this on Longwave 198 frequency, as we are out of range here in Ireland from BBC FM transmissions.
The BBC pollute the longwave 198 frequency with day-long cricket commentaries and in order to get the normal Radio 4 programmes we have invested in two identical Roberts WM202 internet radios.
Transmissions on FM, Longwave and AM tend to be in perfect sync., but we have found that the internet radios are A/ some 20-odd secs. behind normal radios, including the chimes of Big Ben, but B/ out of synch. with each other in adjacent rooms!!
Why two identical radio sets picking up Wi-Fi internet transmissions should be several seconds out of synch. totally baffles me. It's got nothing to do with the distance from the WI-Fi source either, as the one further away is sometimes ahead of that one right beside the source, but not always!!

Ideas?

Tom K.

[skirted_in_SF]

I'm going to stick my neck out here, and someone with greater geek cred (Carl?) is welcome to correct me.

I believe each of your internet radios has to make its own connection with the server in question. My guess is the each gets a different route to the server, each with its own set of latencies.

I can sometimes get a similar problem switching between two Public Radio (FM) stations broadcasting the same program. I just chalk it up to different delays as the signal makes it way from the distribution satellite through their respective control rooms and transmitters. The lag can be as much as two or three words in a news story.

[crfriend]

The main problem here is that "Internet radios" are nothing of the sort -- at least in the classical sense. The only way they count as radios is that they use radio-frequency communications to carry the data that makes up the programme that one is interested in listening to.

Quite unlike classical radio, where the program is converted to radio-frequency electrical signals and then fed into a transmitting antenna which serves as a "single source" for all receivers, audio transmission via IP (Internet Protocol) involves digitising the audio feed and setting up individual point-to-point connections (or "sessions") through which this data is sent. This is the first point where timing discontinuity will creep in as one particular session cannot be processed at the same precise instant as any other session, nor can those data be shoved down the wire at precisely the same instant. This means that one will get temporal discontinuities even in the same room as the server, and who even says that both "radios" are even connected to the same server?

There will be some maximum time-frame which cannot be exceeded, but that's based on how the show in question is produced and how it's archived at the server end, and there will be some minimum discontinuity as well ranging from something one would need electronic gadgetry to measure on up to several seconds. The very large delay between broadcast time and IP time does not surprise me one bit; there are myriad factors that can account for that including the possibility of a deliberate delay. As far as the chimes from Big Ben being delayed is concerned, that's just plain wrong, and the takeaway is that you don't set your clocks at home from that "signal".

The "Internet" -- like all things digital -- is fairly rotten at timing because event's don't happen in real time; there is always some form of delay. In practise, those delays can be ascertained and accounted for, and accurate timestamps gotten (see NTP ("Network Time Protocol") for more details than a non-geek can stand), but those are very different from an audio programme. Encoding, compression, routing, decompression, and decoding just add to the temporal distortion. So, while "old fashioned" radios pull electromagnetic energy directly from the air and process that into the audio programme the Internet "radio" gets its data from a combination of copper, glass, silicon, and finally (possibly) a local digital radio. I understand the next big development will be wireless television.

Have you tried a larger antenna for your "old school" radios?

Stuart -- The days of "live" network broadcasting, especially in radio, are long behind up. The programmes you're listening to are almost certainly produced in advance and distributed to the local stations for broadcast. In the "old days", this meant cueing up a tape and hitting "play" when a time-signal said, "Go"; nowadays, it's all digital, but there's always the human element involved, so somebody may have flipped the switch a few seconds behind somebody else at the other local station. Whilst there are propagation effects on satellite-transmissions, the odds of being more than several milliseconds out between two antennas at adjacent radio stations are nil.

[Kirbstone]

Thank you both, Stuart and Carl for your learned input and explanations. I can now see the logic in an American businessman's response to my question put to him at a coctail party: 'Have you ever considered doing a PhD?'.........'Man, if I wanted a PhD, I'd HIRE one!'

So, courtesy of this forum I can have amazing knowledge sent in my direction by just asking!!!

Tomorrow I'm off on the Briny Baltic pulling and heaving on ropes and shanty-singing my head off with the rest of 'em (26 crew), so I'll be off limits for a week. We won't have the luxury of a B&B on board to feed us all, so we're sharing that. My forte though, is the washing up!.

Yo-ho-ho, and a bottle of.....Schnapps!

Tom

[Big and Bashful]

Thats strange, my post dissappeared.

[crfriend]

Tomorrow I'm off on the Briny Baltic pulling and heaving on ropes and shanty-singing my head off with the rest of 'em (26 crew), so I'll be off limits for a week.

There is part of me that is sorely tempted to fire off a large volley of vitriol towards the Irish Isle, but I really don't think I have it in me. At the moment, I'm "on the clock" 24 hours a day until Thursday, so it's going to be a long week even if I do supposedly have Monday off as a holiday. At least I get to go and dance around on Boston Harbor one last time this year on the 9th; doing so on a large vessel gets more appealing every time I head out on the briny. I just hope Katia doesn't catch us in her crosshairs.

And you're welcome for the radio bits. Even if they're not really radio.

[crfriend]

Thats strange, my post dissappeared.

If you're reading this now it's too late, but I've had good luck with pegging the "back" button a few times in the hopes that the editing window will come back.