Let’s stomp out the confusion surrounding the term bitrate and find out exactly what it is and what it does.
Many artists pursue a creative career because academic studies weren’t their strong suit. While I enjoyed English studies in school, my math and science grades are better left tucked away in my history box in the attic.
Therefore, it’s somewhat amusing—and slightly ironic—that being so heavily involved with cameras and video editing means I’m continuously surrounded by numbers, most of which need to be calculated.
Whether that’s working out the f/stops between the foreground exposure and the sky, calculating what shutter speed to use to maintain a 180-degree shutter angle, or figuring out if this 256GB card will give me at least thirty minutes of record time at 1700MB/s.
One aspect that can be exceptionally mathematically confusing is bitrate. If you’ve exported videos, I’m sure your NLE has asked you what bitrate you want to use. I’m equally sure you’ve been somewhat perplexed at deciding what bitrate is correct—or just left wondering what bitrate is.
So, let’s find out what it is and what it does.
Original image by Pure Solution.
What Is Video Bitrate
It can be infuriatingly easy to confuse video bitrate with other video elements that sound similar.
- Bit depth
While they fall within the same realm of data terminology, they all represent vastly different things. Additionally, we also see megabits used for download speeds—confusing.
You’ll usually see the bitrate displayed as “numerical value bit/s.” However, for video, bitrate is the number of processed bits at any given time. And, that given time is usually measured per second. So, 5,000 bit/s would be 5,000 bits per second.
What is a bit? A bit is simply data. And, the bit rate denotes the number of bits that are processed within a time frame. That is usually a single second.
However, video files are so large in volume, measuring them as single bits isn’t suitable, as the numerical values would be too large to display adequately. Therefore, bit rate is often measured in megabits per second, which is one million bits per second.
On YouTube’s recommended bitrate settings, you can see it’s been condensed into more appropriate numbers, and these are megabits (Mbps), not to be confused with megabytes (MBps)—note the capital B.
Then, in editing software like DaVinci Resolve, the export settings are referenced in kilobits (Kb/s).
Recommended YouTube bitrates.
Using YouTube’s 4K 24fps recommended bitrate at 35 Mbps, let’s convert those numbers through the table.
- 35 Mbps
- 35,000 Kb/s
- 35,000,000 bits
That’s a lot of jargon, I know. So, let’s break it down creatively.
Think of a video file as a box, and inside the box is information on a subject—documents, pictures, audio recordings. The more information inside of the box, the better you’ll be able to understand the subject.
But, if the box only contains a handful of documents and one picture, you might only get a vague understanding of the subject.
That’s like bitrate. The bitrate dictates how much data is transferred per second, and it also directly affects the video image and audio quality. The higher the bitrate, the more data available, and the better video quality.
However, a video file with a high bitrate will be significantly larger (in file size) than a video with a low bitrate because there’s more data to present per second.
Therefore, editors and filmmakers are sometimes caught between a battle of having video files that look the best vs. video files that are easy to upload, transfer, and store.
What Bitrate to Choose
Choosing the right bitrate for your video can be frustrating. Image via GaudiLab.
With that information, it may seem practical to simply bump up your video bitrate to the maximum settings, right? The higher the bitrate, the better the video quality! While that’s true, this only works to a degree. You have to remember that the camera also has a bitrate in which the footage was captured.
Therefore, if you increase the bitrate to an amount higher than the original material, you’re going to be filling your video file with empty information that still has weight. This will then create a large file for no reason.
Additionally, platforms themselves have bitrate limits. After upload, your file is processed and compressed to a usable format on the platform to be delivered to all devices. Again, increasing the bitrate to an illogical level will waste your time rendering, uploading, and processing the video on your chosen platform.
Try using presets to keep your bitrate value at a reasonable level for the platform you intend to share on. Image by Sutipond Somnam.
Likewise, the resolution and frame rate will also play a pivotal role in what bitrate you should use. For example, 50 Mpbs for a 1080p file would be too much. A 4K file will need a higher bitrate because there’s more data to present.
If you’ve been jumping from website to website looking for a recommended bitrate value, this is also why you haven’t found one. Between the recording format and destination platform, there’s a never-ending selection of bitrates to choose from.
However, most editing software will have pre-dialed settings to regulate the confusion. You can select from least, low, medium, high, and best in Resolve. I’ve kept my bitrate setting to “best” for the last four years and haven’t had any issues.
Below are the linked recommended bitrate pages for the most popular video platforms:
Variable Bitrate vs. Constant Bitrate
Depending on what codec you’re using, you may be presented with the option to deliver the file with either a variable bitrate or a constant bitrate. What’s the difference?
A constant bitrate, as implied, is where a video is transcoded with the selected bitrate for the entirety of the video. If you set your bitrate at 3,000 bit/s, it will consistently stay with that data rate for every sequence, even if it doesn’t need such high encoding.
CBR is excellent for knowing how large your file will be, and it’s typically faster to encode than VBR. However, you may be unnecessarily increasing your file size.
Make sure you don’t unnecessarily increase your file size.
VBR stands for variable bitrate, and this setting will adjust the bitrate (to the limit set by the user) up and down throughout the video. The adjustments are based on the data in the frame. If the frame consists of a solid color while the narrator introduces the film, there isn’t an inherent need for a high bitrate, and your software will lower the bitrate.
Conversely, even on a complex scene, while the software will increase the bitrate to accommodate the high data values, it may not do so at the desired level as if using CBR. As a result, it could leave your image slightly degraded than if you used a constant bitrate.
This is a complex encoding process, but it also takes longer to render.
Another thing to note is that some devices that don’t have a lot of processing power may find a video clip with a VBR difficult to playback as the bitrate is constantly changing.
The Tl;dr: bitrate dictates how much data is presented each second, and by having a higher bitrate, you’ll have a better quality video file, but at the cost of a larger-sized file.
Cover image via GaudiLab.