When the neighbour calls the goal before you: why football broadcasts on DTT or the internet arrive late

There are matches that are not forgotten. Those goals in the last minutes that decided history. But I’m sure I’m not the only one who was annoyed by the neighbours at some of those moments. I I already knew they were going to scorebecause I heard the neighbors’ screams a minute earlier. How can there be such a difference? Aren’t they seeing it at the same time as me?

The explanation is simple: it depends on the channel on which they are watching the game. Listening to it on the radio is not the same as watching it on DTT, nor is cable or satellite television the same as internet broadcasts and streaming. Each channel has its own timing and that is why we sometimes hear someone calling a goal before time.

The fastest is the radio

Unless we are in the stadium itself, the quickest way to find out what is happening is to listen to the game on the radio. It is practically instantaneous for several reasons. Firstly, because it is transmitted directly from the transmitter to the receiver. It is a analog signal that travels at the speed of light and requires virtually no signal processing. There is no need to encode or decode the video signal, which greatly reduces latency.

This signal processing is the main culprit of the delay. The more “complete” the signal we receive, the longer it takes to process it. And although technology has improved a lot, the comparison with radio always ends up in favour of the latter.

Television requires a larger bandwidth and a more complex infrastructure. Radio, on the other hand, is the opposite. Because it is such a simple broadcast, the infrastructure required is also much smaller. Radio is based on simple devices and there is virtually no congestion in radio transmission. It is a reliable method that has been around for many years. If what you want is to be the first neighbors to sing goalthe radio is what you need.

DTT is already behind (and the Internet even more so)

The next channel with the least delay is Digital Terrestrial Television (DTT), but here it is already a few seconds late. The delay is due to the signal being captured by the camera and then sent. This process is fast, but it must be compressed in order to be sent and then decompressed. Depending on the quality of the signal it will take more or less time..

This is why UHD channels have more delay than SD channels, because this process of decompressing the signal takes more time. Beyond DTT, we have satellite or cable television. In the case of satellite television, more delay is added again because the signal must reach the satellite and return.

Finally there are internet broadcasts. From IPTV to watching the matches on streaming services such as RTVE PlayMovistar+ or DAZN, among others. OTT (free-to-air ‘over-the-top’) services are those that add the most delay. This is because the signal is captured and must be encoded in digital format for transmission over the network.

With internet streaming the signal must go through a server and a content delivery network (CDN). This journey can be seen affected by both network status and server capacity in every match. CDNs are responsible for distributing content efficiently, but despite having improved over the years, they continue to add tens of seconds of delay to broadcasts.

It doesn’t end here. To ensure smooth streaming, streaming services use a bufferIt is a small amount of data that is temporarily stored on the device before the content is played. It is a kind of buffer to anticipate possible problems such as cuts. But of course, it has the impact of adding delay as well.

These are technical additions that cause an increase in delay. We are not taking into account the direct delay, sometimes added by the operators and broadcasters themselves to give them room to act in case they want to edit a live broadcast or delete something.

The future lies in better protocols

Zero latency is impossible to achieve, but it is feasible to think that in the future it will be possible to achieve a sufficiently low delay on the Internet to be at least at the level of DTT.

The first thing to improve is Compression and decoding algorithmssuch as AV1. This will allow the video signal to be sent faster and with less loss of quality. Reducing the buffer size will also help reduce lag.

The next point that can be improved is with CDNs. Here it is up to the companies that provide this tool to improve their infrastructure.

But where a great improvement has been noticed is with the arrival of QUIC, the protocol created by Google that has become a standard and is replacing TCP, which has been active since 1974. QUIC is the protocol that has been implemented in HTTP/3 and its function is to dictate how information is divided into packets, sent over the Internet and then re-formed. According to W3Techs dataQUIC is used on approximately 8.1% of all web pages.

Using improved transmission protocols such as QUIC will help reduce latency and help streaming services to offer football matches with a shorter delay compared to other broadcasts.

Football matches are one of the most popular live broadcasts nowadays. We all gather together to watch them live, but we have to be aware that taking that image home requires many steps.

Image | Telefónica Audiovisual Services

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