An introduction to low latency streaming
Many of us are aware of the delay when it comes to video data transmission.
So what exactly is low latency? Do you require reducing latency for all your live events? Let's answer all this plus more in this tutorial.
A primer on low latency
Low latency refers to the smallest delay for video data to transfer between your player and the screens of your viewers.
The lower time to transmit data results in a better video experience, and also facilitates interactions. Here's the thing For a low latency experience, it is necessary to sacrifice lower resolution or video quality.
Fortunately, there are not many live events that require the use of low latency.
It is essential when you live stream events for real-time interaction or watching experience. In these cases viewers expect to see what's going on and/or be a part of the action during the course of the event. This means you won't be able to afford excessive latency, and have to stream in lower than 4K video resolutions.
Although this is low-latency streaming, let's dig into the details of when and how you can achieve it.
What exactly is low latency?
When translated, latency literally means 'a delay in transfer.'
In the context of video latency, that's the amount of time it takes from the footage you have taken from your camera to it playing within your viewers' player.
Therefore, a low latency will mean lower time spent in moving video data to point A (your stream's headquarter) and to the point of B (your viewers).
Similarly, a high latency means more time in video data transfer from the live streamer's viewers.
What exactly is considered to be as a low latency?
In accordance with industry standards low latency live streaming video is less than 10 seconds while streaming broadcast tv ranges from 2- 6 minutes. Based on the use you intend to make and requirements, you can attain ultra-low latency which lies between 2 - 0.2 seconds.
But why do you need low latency in video streaming? It's not necessary to have high latency on every live stream that you host. However, you will need it for each interactive live stream.
What is important here is how much interaction your live event requires.
Therefore, if the event you're planning involves such things as a live auction then you'll require a low latency for your stream. Why? In order to make sure that every interaction is on time - and without delays as that can cause some users to gain an unfair advantage.
Let's look at more examples of these usage cases later.
When do you need low latency streaming?
The greater participation in live streaming your event demands, the shorter transmission time you will require. So, your attendees will be able to take advantage of the event in real time without any delay.
Here are instances when it is necessary to stream at a low-latency:
- Two-way communicationsuch as live chat. Live events include live chats where Q&As are involved.
- Experiences in real-timeis essential such as with online games.
- Requires audience participation. This is the case, for instance, when it comes to cases of online casinos, gambling on sports and auctions that live.
- Real-time monitoring. Examples include mission to search and rescue as well as bodycams that are military grade, child and pet monitors.
- Remote operations which require constant connections between remote operators and the machinery they manage. Example: endoscopy cameras.
When should you use streaming with low latency?
To summarize the various scenarios that we've discussed above It is necessary to have low latency streaming when you're streaming either:
- Time-sensitive content
- Content that requires real-time audience interaction and engagement
However, why shouldn't you use low latency for all your video streams? After all, the lower the time your video content takes being seen by your viewers, the better, isn't it? But, it's not so simple. The low latency comes with negatives.
The disadvantages include:
- The low latency can compromise the quality of video. Why is this? High video quality can slow down process of transmission due to the huge file size.
- There's not much buffered (or loaded) content in line. This means there's little room for error should there be a network issue.
In the event of live streaming, a streaming service like quickly pre-loads some content before stream to viewers. So, in the event of an issue on the network, it will play the content buffered, and allows the network-caused slowdown to recover.
Once the problem with the network is fixed when the issue is resolved, the player downloads the best quality video possible. However, all this happens behind the scenes.
The result is that viewers receive continuous, high-quality playback experience unless, in the course of events, a serious network mishap occurs.
When you opt for low latency it's not as much playback video that the player prepares. This leaves you with minimal chance of error when a network issue strikes suddenly.
The fact is that high latency is useful in some instances. In particular, the longer time-lag allows producers chance to remove inappropriate content and profanity.
In the same way, if you can't compromise with the broadcast quality of your video, raise the delay by a small amount so you can offer a high-quality viewing experience and have some room to correct errors.
How do you measure latency?
The definition of low latency streaming as well as its use cases in the past, let's see how you measure it.
The technical term for low latency refers to the time measured with a unit called the round-trip duration (RTT). It refers to the length of time it takes a data packet to go between points A and B and to return back to the origin.
Now to calculate this method, the best way to do it is to include time stamps to the video stream and request a teammate to watch the live streaming.
Have them look for the exact time frame that will appear on the screen. Now add the timestamp's duration from the time the viewer saw the exact frame. That will calculate your time of arrival.
Alternately, you can ask your teammate to follow your stream, and take a cue when it comes. Then, record the exact time that when you made the cue sound on the live stream and when your assigned viewer saw it. This will give you latency albeit not as accurately as the above method. However, it's good enough to give you a rough estimate.
How do you decrease the video latency
How do you get the lowest latency?
The reality is that there's a myriad of factors that impact video latency. From encoder settings to the streamer you're using, many factors come into play in.
Let's take a take a look at these elements and ways to optimize the way you use them to decrease latency , while ensuring that your quality video doesn't take the biggest hit.
- Internet connection Type. The internet connection affects speeds and rates of data transmission. This is why Ethernet connections are better to stream live than wifi and mobile data (it's recommended to use them for backups, however).
- Bandwidth. A higher bandwidth (the amount of data which can be transmitted at one time) results in less congestion and more speedy internet.
- Video file size. Larger sizes take up more bandwidth in transferring from point A to point B, which increases time to transfer and vice versa.
- Distance. This tells you how far you're from your internet source. The more close you are to the internet source closer to the source, the more quickly the stream of video will move.
- Encoder. Choose an encoder that can help maintain low latency when communicating signals directly from your device to the receiving device in the shortest duration as you can. However, make sure that the encoder you select is compatible with your streaming service.
- streaming protocol or the protocol that transfers your data packets (including video and audio) directly from your computer to the screens of viewers. For achieving low latency, it is necessary to choose the right streaming protocol to minimize data loss while introducing less latency.
We'll now look over the different streaming protocols that you are able to pick from:
- SRT It is a protocol that effectively transmits high-quality video over lengthy distances with minimal latency. But, as it's new, it's still being used by technology, including encoders. The solution? Combine it with other protocols.
- WebRTC: WebRTC is great for video conferencing however it has a few compromises on video quality since it is focused on speed, primarily. However, the issue is that a lot of video players can't be used with it due to a complex set up for deployment.
- High-latency HLS is great for low latencies of up 2-seconds. This makes it suitable for interactive live streaming. But, it's still an undeveloped specification and support for implementation is currently in the works.
Live stream with low latency
The streaming of low latency is feasible with a speedy connection to the internet, a good speed, the most efficient streaming protocol available as well as an efficient encoder.
Additionally is that closing the gap between your computer and internet connection and using lower-quality formats for video can help.