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What is frame rate (fps) for live streaming

Any video is a set of separate pictures - frames. The video can be compared to a digital flipbook. Flipping the picture quickly creates the illusion that it is moving. Hence, frame rate refers to the speed at which the frames are captured and displayed. That’s the basic concept behind the frame rate.

How to measure it

The unit for frame rate is fps. The number of frames determines the smoothness of the action in the frame. More frames mean smoother movements, clearer moving objects. 

When there are few frames, you will see jerks and a blurred movement.

FPS depends on the hardware of your smartphone, computer, laptop or tablet. From his video card, processor, etc.

What is update frequency

A screen's frequency of updates depends only on the screen itself, and sometimes on its software settings. The frame rate (fps) is not the same as the refresh rate of the screen, which is measured in hertz (Hz).

For example, 60 Hz means the screen is updated 60 times per second. 120 Hz means 120 times per second. 400 Hz - 400 times per second. Human eyes cannot see beyond these limits, so if you see greater numbers, this is pure marketing and likely a scam.

How are fps and Hz related?

Let's say your hardware produces 300 frames per second. The maximum number of frames you will see out of these 300 will be 60 if your monitor only runs at 60Hz.

Your file's fps measures the number of images per second, while your screen's Hz measures the frequency at which the screen refreshes.

And this is determined not by your file, but by the device to which it is transmitted and displayed.

You simply won't be able to view all frames of the file if the display characteristics are less than those of the file.

An average refresh rate of 60Hz at 60 frames per second is sufficient for normal use.

What's the shutter speed

It is important to note that this term should not be confused with frame rate. The terms refer to different video workflows.

Shutter speed is about video recording, refresh rate is about video playback.

So how does fps come into play here?

The camera on which the recording is taking place determines the frame rate. Cameras have shutters that control how much light passes through the lens.

Short shutter speed - little light;

Slow shutter speed - lots of light.

This is related to fps as the most common goal is to capture natural movement. This requires the shutter speed to be about twice as fast as the frame rate.

What are the origins of FPS?

The history of frame rate can be traced back to cinema. A little over two hundred years ago (1800s) film had low sensitivity. Just imagine waiting several hours to take one picture. And wait in a motionless pose. There are some old photos in which you can see a person leaning on a prop.

After the turn of the 19th century, all the props used by photo salons for clients were thrown away, as the situation changed. Finally, photographers were able to not only take several images, but also scroll film rolls. The whole process was done by hand so far, but this is how cinema began. Due to the fact that everything was done manually, the frame rate varied from 14 to 26 frames per second.

In the 20th century, mechanical rolls were invented. This led to the development of the 24 frames per second standard. In this range, it proved most convenient to sync audio with the picture when sound appeared in the cinema.

Why is FPS important?

When it comes to creating videos, frame rate can be viewed as a block base.

It affects the smoothness and viewing experience, and it also creates style. You may not notice the difference if you watch a video with a non-standard frame rate, but something will seem unnatural and unreal.

24 frames per second is the golden ratio in the world of video in the sense that it conveys the perception of the human eye in the most accurate way. It is therefore natural for us to perceive this frequency.

The high frame rate makes it easier to watch sporting events where participants are actively moving. Slow motion replays provide more frames so you can see specific moments in detail.

Therefore, when choosing a frame rate, consider what you are shooting.

There is a misconception that the higher the frame rate, the better the quality.

But the fact is that if you apply too high a frequency incorrectly, the result will be a stream that cannot be played fully on many devices, or is too crisp.

To determine your video specifications, ask yourself 4 questions:

  • How much action is in your video?
  • What do you need from the video more - cinematic feel or crisp image?
  • What displays do your viewers have?
  • Do you need a slow motion video display?

After that, it will be easier for you to navigate the frame rate and apply it to your content.

Consider 4 options that apply:

  • 24 fps;
  • 30 fps;
  • 60 fps
  • 120+ fps.

24 frames is your option if you are shooting a movie or TV show. We have already mentioned that this is the most natural type of display of reality on the screen for the human eye. There are video games that use this frequency for the cinematic effect.

30 frames is considered the standard in American TV. Notice how bright the news or sports broadcasts seem to be.

60 frames is fine if you are doing live broadcasts. This standard is also suitable for streaming video games with a lot of movement, and sports broadcasts (when you need to slow down the frame).

Of course the average person won't notice the difference. During the transmission, when video is compressed for delivery, artefacts will form at 60 frames per second, which will eventually degrade the quality of the picture.

120+ frames is a rare standard that you can only meet in eSports to broadcast all the same slow motion frames of a dynamic moment. Only a display with playback characteristics of 144-165 Hz will fit this format.

For US streaming, 30 frames will be enough from capture to transcoding. It is better to stream 25 frames if you are streaming for Europe, although 30 frames can also be effective.

For best user experience, consider the technical specs of the sites you are streaming to aswell.

For example, YouTube Live - 60 acceptance frame rate.

Facebook Live only accepts 30. But you can use an encoder, connect it to the Facebook interface (API) and do 60 frames per second.

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