What is video latency and why is it important
Let's explore some of the most commonly asked questions about video latency.
Knowing how to deal with latency is most important for those who deal with real-time video content: in the field of entertainment, e-sports, media and other OTT content providers.
What is video latency?
In the world of video, latency is a by-product of stream processing and delivery. It is called through, and often referred to using the term "glass-to-glass".
Latency accounts for the period of time between the capture of what is happening on the camera and the moment it is displayed on the screen of the viewer.
In the context of live streaming, video latency depends on technical factors, including how streaming is set up on the platform.
A latency is considered undesirable since it prevents your viewers from receiving information directly in real time. However, sometimes it occurs unintentionally.
But there is also another type of “latency” – in order to synchronize streaming sources and add cinematic elements, producers need a small amount of time between capturing and transmitting video. The main thing is not to confuse them.
If you're designing a system for video content, whether it's a live streaming platform or a drone piloting program, your goal will be to minimize latency.
In general, the lower the latency, the better for your product and your users.
In case you do not address this short period of time, you will lose your end users eventually, as they will get a subpar experience.
For example, you watch football through an OTT streaming platform. And your neighbor is watching the same match on classic TV. He will already know who scored the goal while you’d be still waiting for it to happen, if the latency is not addressed properly.
What is the acceptable latency for video?
Latency is usually measured in units of time, such as seconds or milliseconds (ms).
The waiting time can vary from minutes to milliseconds.
A latency of 300 milliseconds or less is considered ultra-low.
If your product is an interactive application, you’ll need to get to 200 milliseconds and try to get as close to real time as possible.
There are 4 levels of unwanted latency (all indicators are approximate and may vary slightly in different sources):
1.Typical latency. The time interval is from 18 to 30 seconds. This is okay, if your broadcast is not interactive.
2. Broadcast latency can occur on both traditional TV and OTT platforms and ranges from 5 to 18 seconds. If you are broadcasting news or broadcasting from a football field or other sporting event, this is normal.
3. Ultra-low latency - ideal for live video conferencing. These are indicators below 300 milliseconds.
The peculiarity of low latency is that it does not have an absolute value. But everyone who publishes interactive content strives for it to be less than 1 second.
What causes video delay?
As part of the video processing, when temporary storage is required, buffering may occur to ensure the video reaches the user's screen without distortion.
An example of this is the translation of pixels captured by the camera into an image displayed on the display. The time it takes to convert a short piece of a video also depends on the frequency of the frames.
For example, take a one-frame delay in a 30fps video.
An HD 720p video frame has 720 horizontal lines, so a single line delay at 30 fps is 1/(30*720) = 0.046 ms latency. At 1080p at 30fps, the same single-line delay is less than 0.030ms.
Latency also affects video quality.
Due to adaptive streaming, platforms will degrade the picture quality to balance the speed and quality of playback.
Video latency is affected by three main parameters :
internet connection speed
You can learn more about the encoder settings in the article : What is video encoding?
How to reduce latency if you are a gamer streamer
To prevent lags from affecting the gameplay, you can do a few simple steps:
1. Check your internet speed and bandwidth.
2. Make sure your hardware is set up correctly. To do this, find out the location and connection of the remote server, as well as diagnose the equipment.
3. To cut the latency down, you need to shorten the route that data packets travel from the source to you. For example, if your router is located far from the console, this also slightly affects the quality of the connection.
Make sure there are no walls, floors, furniture, or other physical objects between the computer and the router that could interfere with the wireless signal.
Few people know, but household appliances also affect the signal: wireless speakers, a microwave oven, a mobile phone, a charger, etc.
4. Close all background websites and programs.
5. Connect your device to the router with an Ethernet cable.
6. Play on a local server.
7. If all of the above did not help, replace the router and possibly upgrade your broadband package.
How else can you reduce video latency without sacrificing image quality?
1. When you choose a hardware encoder/decoder, pay attention to the latest generation devices. They are designed to be able to maintain a delay below 50 ms. They also have good processing power, which allows you to compress videos using HEVC while maintaining image quality.
2. The choice of video transmission protocol is also important. We recommend the open source protocol Secure Reliable Transport (SRT). It prevents packet loss during video transmission by correcting errors using ARQ (Automatic Repeat reQuest).
How to find a balance between latency and bandwidth and video transmission quality?
For balance, make compromises.
For example, for video surveillance and ISR, a high-resolution video is not required. It is more important to try to minimize the latency.
But if in your case the broadcast quality is more important than latency, slightly increase the delay so that the video would be displayed without errors and losses during transmission.
Even though technology still forces us to compromise, the delay in live broadcasts is manageable.
For example, flexible broadcasting can be achieved by choosing a streaming platform where all technical features are taken into account or you can fine-tune it yourself.
With Callaba Cloud, you get the full range of video broadcasting technologies within a single product and API.
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If you are interested in ultra-low latency delay and good video quality, then you will be glad to know that on this site you can organize SRT, MPEG-2 / .TS, RTSP, RTMP, HTTP, UDP, HLS / m3u8, MPEG-DASH /mpd broadcasts in your region or worldwide.
Video transmission is possible in HD, Full HD, Ultra HD, 4K and 8K resolutions.
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