Photo by Spencer Imbrock on Unsplash

Forget bandwidth

It’s all about latency

The big advantage of 5G is the lack of delay that can be achieved whilst streaming. Yes, the bandwidth potential of 5G is huge, but this is not the issue. We already have enough bandwidth with fixed broadband and 4G is usually good enough.

The advantage of low latency needs to be looked at from two perspectives:

• The delay between musicians
• The delay from the stage to the audience

Two musicians standing a few meters apart without any onstage monitors can just about play in time with each other due to the time it takes for sound to travel between them. Any further away and it starts to get difficult to play in time, unless, of course, you have in-ear or onstage monitoring. So, for musicians to play in time with each other the latency needs to be in the region of milliseconds. 

The musicians in this video are in two rooms that are next to each other. This means that there would have been a direct 5G connection between the musicians. As distances get longer, then the connection requires more links in the chain. The more links there are, in the chain, the more processing happens, which increases the latency. Light travels fast but it is finite and fibre optic cables slow this speed down, so this means that there will always be a limit to the distance between musicians. But it is technically feasible for the musicians to be located within say, one thousand miles of each other.

A large arena can put a distance of hundreds of meters between the stage and the audience. This equates to hundreds of milliseconds for sound travelling in the air. This delay can be clearly seen when watching the images projected either side of the stage. The image and the sound are out of sync due to the difference in the speed of sound and light, so the reaction of the audience can take up to a second to get back to the musicians for very large venues.

So we have different acceptable levels of latency. For the musicians, it needs to be in the order of milliseconds. For the audience, it needs to be in the order of hundreds of milliseconds if we want to have a good connection between the musicians and the audience. When someone is viewing the stream on two devices at the same time, say their phone and their TV, then the delay can be hundreds of milliseconds, but the delay between devices should ideally to be in the order of tens of milliseconds.

Currently when watching a live stream on two devices at the same time can very often be out by tens of seconds. It is currently possible to reduce this to less than a hundred or so milliseconds with currently available technology. Depending on what technology is used.

Streaming technology usually stores tens of seconds of video before delving it to the viewer. The reason for this so that if there are problems with the delivery of the video stream, it has a buffer of content to draw on. Technologies that have lower levels of latency achieve this by sacrificing the quality of the stream, which means that you are more likely to see pixelation of the video and drop out of the audio. So there is a trade-off between consistency of continuous delivery and latency. There are other ways of dealing with this, for example, duplication of the video over multiple paths, but this adds significant cost.

We believe that live music streaming should be about the connection between the audience and the musicians, so low latency needs to be the primary consideration. Latency in the order of hundreds of milliseconds between the musicians and the audience is acceptable as this is the same as in a large arena. The delay for the audience can be greater than the delay fro the musicians.

The audio stream to the audience will be high quality, it’s just that there may be the odd bits missing if the connection is bad. The audio needs to be without data compression because it takes time to calculate how the audio data can be reduced. So data compression of the audio would add to the latency and needs to be avoided because of this. Some forms of video compression can be done ‘on the fly’ so this does not necessarily apply to the video component of the stream. This lack of data compression of the audio is not a problem as there is plenty of bandwidth available for this.

The real benefit of 5G for live music streaming videos is the low latency that 5G delivers over other technologies.