DTT

This World Cup has involved a meeting in the field with friends in every match in Spaina fairly typical scene that shows that, when there is football (and even more so when La Roja plays), everything comes to a standstill. We take the TV out on the porch, grab some chairs, have some snacks and dinner, and what more could you ask for. Well yes, one thing is: don’t let the neighbor spoil the surprise of the goals. Since we did not have a coaxial cable antenna at hand, we streamed through the app Movistar Plus+. The thing about streaming is that, generally, the retransmission it’s more late than the signal that is emitted from DTT. It is not particularly annoying as long as there are no cuts, but an event like a World Cup, where each goal is shouted out loud, can become quite a nuisance. And even more so when the signal is more than a minute late, as was the case with us. So I couldn’t think of anything other than to explain the reasons why this happens and its possible solutions. The traditional antenna is faster than it looks Traditional television, which is received via antenna, also has its own delay. It has never been a one hundred percent instantaneous broadcast, since the networks They usually apply a small margin between five and ten seconds, precisely to be able to cut off in time if something inappropriate happens live. This cushion has existed for decades and is the same for all viewers who watch the signal on the antenna. The difference is that this delay is short, stable and homogeneous. Everyone who watches the game on DTT sees it, more or less, at the same time. However, in streaming things change. The (much longer) journey of a signal over the Internet To understand why streaming always arrives later, we have to follow the path that the image takes from the stadium to our devices. And this journey goes through several stages: first with the capture of the image, then with encoding, transcoding, distribution and, finally, decoding on the viewer’s device. Each of those steps adds timeand none are instantaneous. Image generated by AI with Gemini The key is how that video is distributed over the internet. The vast majority of streaming platformswhether large general services or sports applications, use protocols such as HLS or its equivalent DASH. Both work in a very specific way, since the server does not send a continuous stream of video, but rather cuts it into small fragments of between two and ten seconds in length, which the player downloads one after the other. So that the playback is not cut off or stuck if the connection fails for a moment, the player does not limit itself to downloading the fragment that is to be seen at that moment, but also also save several fragments aheadsomething we call “buffer“. This mechanism prioritizes making the video look fluid over seeing it at the exact moment it happens, and that is precisely the price you pay in seconds of delay. To this we must add the distribution through the so-called CDNs (content distribution networks), which are the infrastructures that allow millions of people to watch the same game at the same time without the original servers collapsing. The CDN77 company calculate that, adding network latency, transcoding time (about five seconds on average) and the player’s own buffer, common HTTP protocols generatea total delay of between 25 and 40 secondsfrom the moment the play occurs until it reaches the viewer’s screen. Amazon Web Services, which provides technical support to numerous streaming platforms, matches in that the player’s safety margin is a decision made by each application, and the greater the margin, the more protected the playback is against cuts, but also the later the image reaches the viewer. There are extreme cases. FEED technical magazine remember that, during the last Euro Cup, many viewers received the notification of the goal on their mobile phone before even seeing it on the screen streaming, and also cites the case of boxing match between Mike Tyson and Jake Paul broadcast by Netflix, which had significant loading and lag problems. And there is no solution? It’s not that the platforms don’t want to reduce the delay, it’s that they want to do it without sacrificing image quality or connection stability It is complicated and expensive. In current streaming, each application distributes the content through its own distribution networks, which causes the delay to vary from one service to another, something that does not normally happen with classic television, where all viewers usually share the same delay. This is precisely why “low latency” versions of common protocols, known as LL-HLS and LL-DASH, have begun to appear. These variants allow the player to start downloading and to show a video fragment even before that fragment has completely finished recording, instead of waiting until it is completely closed. It is a technical change that can cut the delay from the usual 15-30 seconds to just two or five, depending on collect the Dacast platform. Some chains have already begun to apply it in practice. From FEED they count that Sky Sports launched a low latency version of its main channel this year that has managed to reduce the lag by 20 seconds compared to the previous version, and that the BBC has done its first tests of low latency streaming on its iPlayer platform to measure how this technology behaves on a large scale with the current internet infrastructure. What can you do While waiting for these technologies to become widespread, something that in an event with the global audience of a World Cup is neither easy nor cheap to implement, the most practical recommendation is still to turn on the antenna whenever you can, if you don’t want your goal spoiled, and flee from WhatsApp and social networks at that time. Cover image | Wemax Projectors (Unsplash) and RTVE In … Read more