Video Bitrate – the Basics Explained

What is “bitrate” and why is it an important element of video recording, encoding and exporting?

When we are setting up our camera for video recording, most of us understand the resolution setting. This is directly related to the frame size and ratio, so we can “see” the difference. When it comes to setting bitrate it’s less clear.

Put simply, bitrate is measured in bits per second. This is the amount of digital bytes of information being processed by your camera (or other device) every second.

What is video bitrate?

Film is a very long strip of celluloid containing thousands of frames. Each frame will be the same quality, no matter how you project that frame. This is one of the reasons some people still argue for the use of film. Just like the vinyl vs CD or digital file argument.

With digital, however, the image information is turned into light (or light turned into image information) using a computer. Video is recorded or played back from a stream of digital information. Your digital camera, projector or TV requires a processor to convert all this information.

Go large

Imagine that digital video is represented by people coming to buy burgers at your fast food restaurant. If you get 1 customer every 10 minutes, you can probably handle that by yourself. If you have 1 customer every 5 minutes, you might now need to employ a chef while you take the orders.

But if you now get 1 customer every minute, 1 chef and 1 order taker isn’t going to be enough. Pretty soon you’ll both be exhausted and overheating, and you’ll start making mistakes. Burgers will get dropped, which just makes everything worse as you have to re-do orders.

Meanwhile, angry customers are starting to form queues out of the building and down the street…

So you hire more staff.

Now you have 5 people taking orders and 5 making burgers. Your restaurant is able to cope with 1 customer a minute. Just about. But if you start getting more than 1 per minute, you will need more staff. Not only that, you’ll need a bigger restaurant, with more tables and a bigger kitchen…

Camera Processors

The point of this story is to illustrate how bitrates work and how they relate to things like resolution. Because just having a higher number doesn’t always equal better quality. If you hire too many staff without expanding your restaurant, there won’t be room and your staff and customers will have a bad experience.

Likewise with bitrate. To handle all that extra information you need a bigger processor. But that’s not all.

Many people shooting video on their smartphones complain of their device heating up when shooting at high resolutions and frame rates. This is for 2 reasons: 1) small processor and 2) small camera.

A small processor trying to process high bitrates will heat up like burger chefs trying to cook too many burgers too quickly. This is made even worse when your processor is housed in a tiny box like a smartphone case. In this condition, burger chefs drop burgers and video processors drop frames (and cause crashes).

How many bytes can you take?

The only way to fix this problem is either to reduce the amount of information processed per second, get a faster processor and/or house the processor in a bigger case.

The amount of information being processed in 1 second of video = bitrate + resolution + frame rate + bit depth.

Now, you could also say bitrate is determined by resolution, frame rate and bit depth. So mathematically it would actually look like this:

Bitrate = resolution + frame rate + bit depth

Yes, our restaurant has 3 managers and they’re called Resolution, Frame Rate and Bit Depth. These managers are very demanding and insist our exhausted bitrate workers operate at the limits of their capabilities.

So we might wonder – if it’s determined by other factors – why we can set bitrate at all? The answer is down to how digital media works.

A frame of film = a frame of film. But a frame of film degrades slightly each time you make a copy. On the other hand, digital can be copied an infinite amount of times without losing quality (and lo, online piracy was born).

For this miracle to take place, there is a payoff. And that payoff is that quality is limited by files sizes and processor speeds. Digital video will always contain some level of compression and digital compression comes about by removing information.

Digital video parameters can be almost infinitely adjusted to try to set the right balance between looking great and being practically useful. Your incredible 8K, 120fps, 10 bit video running at a bitrate of 1000mbps is useless in the real world as no computer process it, no TV can play it, no broadband can deliver it… and so on.

So when we set these parameters, we must take into account the limits of the technology available to us.

Why do we set bitrate?

As I was saying, this is down to the way digital media works. It’s down to the way information needs to be removed for practical purposes (compression).

So if we decide to shoot 4K at 60fps in 8 bit this will determine the bitrate. But… we can also adjust the bitrate up or down as well, to further fine tune the video quality vs practicality decision.

Like you, I’m just a filmmaker who wants everything to be as simple as possible so I can get on with being creative. I’d much rather not know any of this and let a technician deal with it. However, as DIY no crew filmmakers we need to try to have an understanding of what’s going on.

Anyway, as a filmmaker the more you know about the science the better decisions you will be able to make. And if you get to the point of employing a cinematographer, you will be better able to talk their language.

So what do all these number mean?

Example: YouTube

These are YouTube’s recommended bitrates for videos uploaded in SDR (Standard Dynamic Range) and HDR (High Dynamic Range).

SDR

standard Standard Dynamic Range

HDR

high dynamic range

Use higher bitrates first and compress later

General advice is to shoot and edit at the highest possible quality then compress down later in the process. Bear in mind that when uploading to a streaming platform like YouTube, the video will get compressed further. So what happens in practice is our work gets slowly more and more compressed the further along the shooting, editing, mastering and distribution timeline it goes.

How to set bitrate in FiLMiC Pro

If you are shooting on a smartphone and using the FiLMiC Pro camera app, amongst other things you can also set the recording bitrate. This is how to set video bitrate when using FiLMiC Pro:

  1. Open FiLMiC Pro
  2. Tap the Settings Menu (circular cog icon)
  3. Tap the Resolution tab
  4. Finally, tap the left and right arrow on the middle setting to choose the desired bitrate level

Now, FiLMiC Pro doesn’t give the bitrate number. Instead, the app has setting names:

  • Economy
  • Standard
  • FiLMiC Quality
  • FiLMiC Extreme

Economy is the lowest setting with the lowest quality. However, this will create lower file sizes than the other settings.

Standard is the same bitrate as your smartphone’s native camera app uses.

FiLMiC Quality sets your bitrate above your native camera apps normal rate. In this case, 32mb per second.

FiLMiC Extreme sets your bitrate above your native camera apps normal rate. In this case, 100mbps for 2k, 3k and 4k. At 1080p this target is is 50mbps.

Note the use of the term target bitrate.

FiLMiC say, “When you set a bitrate in FiLMiC Pro you are establishing a target for the camera framework. Depending on the quality of the feed you may see final bit rates that are higher or lower than this target in order to ensure quality. In doing this we can provide for a high quality while also keeping the video file size as low as possible.”

In other words, like many aspects of shooting using a smartphone, this is not a precise science.

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