Low Latency in Live Streaming

By Laura DanielczykSeptember 18, 2020
low latency in video live streaming

Do you really believe that you are watching live streaming events broadcasted live on TV or the Internet in real-time? You couldn’t be more wrong! It takes 5, 15, 30, or even 50 seconds before the signal is recorded, transmitted and received by your TV set or monitor. Every live event you watch comes with a considerable delay!

Such a delay between capturing the image on a camera and its display on the end device is primarily due to the need to encode and transfer large portionsof information from one place to another. This is what we call latency. Learn more about video streaming latency.

What is low latency, and what is it all about?

In the context of video streaming, the so-called low latency is called “glass-to-glass” delay, i.e. the delay between signal recording and its reception. Typically, this delay is approximately 5 seconds. Nevertheless, this term is highly subjective and depends primarily on the streaming protocols used or the amount of data that needs to be transferred.

Traditional cable and satellite protocols have a latency of approximately 5 seconds. But Apple’s HLS streaming protocol is set to 30-second latency by default. On the other hand, protocols with ultra-low latency are able to transmit a signal with a latency of less than one second. These types of streaming protocols are used, for example, in video calls or when controlling devices in real time – e.g. drones at concerts or other cultural events.

So when can we define latency as low? A typical delay in streaming video using protocols such as Apple HLS or MPEG-Dash usually ranges from 30-45 seconds. Unfortunately, this is a lot – getting interactivity with viewers, in this case, is practically impossible. Why? This is due to the need to adapt the protocols to transmission via the HTTP protocol through the use of internal buffers or adaptive broadcast. The implementation of these technologies improves the visual experience, but at the same time, increases the transmission latency.

A lower delay, which oscillates closer to 5 seconds, is provided by such transmission protocols as Low-Latency HLS or CMAF. The situation here is much better here but not good enough to talk about real-time transmission. We are still limited by the accretions HTTP and associated restrictions.

Broadcasts with a delay of less than 1 second is guaranteed by WebRTC and our proprietary software protocol called Storm. However, these protocols are very different from each other. Due to its design, WebRTC is perfect for videoconferencing with a limited number of people. Thanks to the P2P mode and the UDP protocol, you can get great results with it. Unfortunately, when we have to deliver transmissions to tens of thousands of viewers, this model does not work anymore. Here, the best solution will be the Storm protocol, which was specifically designed for this task.

streaming latency continuum

When is low latency especially important?

It is widely known: nobody likes a long delay. Nevertheless, the lowest possible signal transmission latency is of particular importance in only a few cases. It rarely matters for the viewer whether he or she finds out after 20 or 36 seconds that the singer has falsified or that his favorite band has finally entered the stage during a live-streamed concert.

Low latency is especially important in business and professional applications that require interactivity. An ideal example is real-time video conferencing, controlling remote devices, or streaming interactive content. Low latency will also be crucial when streaming live paid video content.

Who Needs Low Latency Live Streaming?

Not every application requires low latency while streaming live video. The most common uses of low-latency streaming include: video chat, betting and bidding systems, and video game streaming.

Video chat

In order to be able to talk comfortably during a videoconference, a sufficiently small delay in video signal transmission is necessary. You must recall a time when you saw a news reporter on the TV speaking to the on-the-scene correspondent. You certainly noticed the long pauses in the dialogue. This is the result of excessive broadcast delay.

Therefore, to provide the interlocutors with a comfortable conversation during a video chat, latency should not exceed approx. 500 milliseconds. This delay allows you to have a fluent conversation without awkward pauses.

Streaming of video games

Video games – especially those played in leagues – are incredibly dynamic and extremely exciting activities. The transmitted video image must be delay-free. Otherwise, the player will – let’s say – shoot enemies that are no longer there for some time, or jump on a platform that departed half a second ago. For streamed games, latency should not exceed 100 milliseconds. This will provide players with appropriate comfort without the risk of lags.

Betting and bidding system

Auctions, bidding or bets are exceptionally exciting activity, in which single milliseconds often count (especially for committed bidders). The speed of the bidding and betting is critical. Therefore, the streaming of signals must be performed in real time in both directions.

Are you looking for software that allows you to stream video with ultra-low latency? Check out our video streaming solutions and choose the one that suits your needs!

Tags: low latency, low latency cmaf, low latency hls, RTMP Tuned, RTSP/RTP, SRT, video chat, WebRTC