Why is content from cable/satellite TV always in sync on multiple TVs, but two iPads with the same stream are pretty much out of sync?
In: Technology
Internet protocol for broadcast (what the iPads are using) isn’t deterministic…the time and route that data packets takes isn’t guaranteed, stable, or generally predictable. So two iPads, even watching the same stream, are going to get data at different times and get out of sync.
Broadcast media like cable or satellite is one signal…everyone gets it at the same time. The only difference is the processing time on the device but that’s so small that you can’t notice it.
Because the content on TV is sent out on the TV channels at all times, whether or not your particular TV is on or off.
A stream on your iPad or other device is started, when YOU start it. So even if you try to time it with someone else, going “3, 2, 1, now”, there’ll be a slight delay between the two of you clicking start. Adding on to that your internet connections are not going to have the exact same bit rates. So overall it becomes very unlikely for two streams to be perfectly synced.
Imagine a stage with one person talking in front of a large audience. It’s up to each member of the audience to pay attention to make sure to hear what they say. The ones in the furthest back might not hear every single word, but they still get most of it, and there’s no way for every listener to make the speaker slow down or repeat the words that they didn’t hear.
Now imagine the same number of listeners, but instead of only one speaker there’s one speaker for every listener. Here it’s critical to make sure that every listener hears every single word the speakers say, so the listener repeats every word to the speaker, one by one, so that the speaker can make sure they heard it. If the listener didn’t hear it, or had to e.g sneeze for a second, they ask their speaker to repeat themselves, and thus fall slightly behind all the other listeners and speakers. Eventually one listener could fall behind so much that they’re way behind all other listeners, so the speaker “skips ahead” to wherever all other(or at least most other) speakers are right now, which means that the listener occasionally miss out on some of the content.
The first is the TV signal being broadcast to TVs; the broadcast does not make sure that all TVs pick up everything or are synced. The second is a livestream where the internet “speaker”(internet protocol) makes sure that the listener(the web browser e.g an iPad streaming Twitch or a news stream) received everything, which is why you can see the stream stutter or lag behind sometimes, a short “pause” if you will, but after too much lag it could skip seconds or even minutes ahead to catch-up.
* Cable/Sat TV/Over the Air are sent out via “broadcast” which means the same data is sent everywhere at the same time.
* If a device receiving that signal doesn’t get some of it, there’s no way to tell the broadcaster, and even if there was, they wouldn’t resend it because it would mess up everyone else’s signal.
* Before we had wires and computers connecting most of the world, we used radio waves to send sound and images out to people and so broadcast was the only way to do it.
* Now that we have powerful computers and wires running to most places, we can send data via a two-way conversation and if the receiving device doesn’t get some of it, it can ask for it to be re-sent.
* This is why two ipads watching the same stream will almost never me in sync.
* That data has to travel over the internet which is a huge and complicated.
* Data gets lost on the internet *all the time*.
* We just never notice because the system is very good at re-sending that lost data right away.
* Cable/Sat TV/Over the Air are sent out via “broadcast” which means the same data is sent everywhere at the same time.
* If a device receiving that signal doesn’t get some of it, there’s no way to tell the broadcaster, and even if there was, they wouldn’t resend it because it would mess up everyone else’s signal.
* Before we had wires and computers connecting most of the world, we used radio waves to send sound and images out to people and so broadcast was the only way to do it.
* Now that we have powerful computers and wires running to most places, we can send data via a two-way conversation and if the receiving device doesn’t get some of it, it can ask for it to be re-sent.
* This is why two ipads watching the same stream will almost never me in sync.
* That data has to travel over the internet which is a huge and complicated.
* Data gets lost on the internet *all the time*.
* We just never notice because the system is very good at re-sending that lost data right away.
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