Bit Rate can be a confusing topic when it comes to videography. You start throwing around terms like resolution, frame rate, HD, and it becomes a jumble of perplexity. In reality, bit rate is none of these things.
Bit Rate is the amount of data encoded per second when you shoot video. The higher the bit rate, the higher the quality of your video. There is, however, a trade off. If you shoot at a high bit rate, you must deal with large file sizes. As your bit rate goes up, so do the file sizes of the videos you are recording. More data per second, more space taken up.
Bit Rate is Not the Same Thing as Resolution
Many people confuse bit rate and resolution. They are independent of one another. Resolution is the pixel size of your video. It does not necessarily determine the quality of your video. Sure, when you have a higher resolution like 4K, you generally have a better looking video. But that is because cameras will generally record at a higher bit rate for these larger resolution files. If we kept the bit rate constant and shot two videos – one at 1080p and one at 4K – you would notice that the 1080p video might actually look better. The 4K video must spread all of this data over a larger pixel area, thus compromising the look.
Let’s look at an example. Take the same standard 1920 x 1080 HD shot. If we encode this video at two different bit rates, you will notice a difference in the quality. Both shots are considered HD because they have a resolution of 1920 x 1080, however they are not equal. The video on the left has a much more pixelated, low quality image. The video on the right is much better quality, but it is over 5 times as large in file size.
Not all cameras shoot at the same bit rate. This is why an iPhone looks different than a GoPro and a DSLR. Each camera has its own options for bit rates at which it can record. Even though all of these cameras can record 1920 x 1080 HD footage, they do not all look the same. There are additional factors like sensor size that affect why these cameras have different looks, but bit rate is a large part of the equation.
Bit Rate on YouTube and other Platforms
Bit rate is measured in megabits per second (Mbps). When you watch a video on YouTube at 1080p HD, the average bit rate of the video you are watching is 8-12Mbps. When you upload your videos to YouTube, the site automatically encodes your video to the ideal settings for each of the resolutions they offer. So if you upload a high bit rate video to YouTube and select to watch it back at 360p, YouTube will have already encoded a file for that size that has a bit rate in the .5-1Mbps range. This allows you to watch most videos no matter the strength of your internet. It is recommended to upload the highest bit rate version of your video – YouTube can’t increase the bit rate of your video.
Because of the development of technology over time, we now consume our content at much higher bit rates than in the past. DVDs played videos at a bit rate of 4-8Mbps. BluRays are capable of holding much larger files, so they play videos at 24-40Mbps. Hulu and Netflix are now pushing these limits as well, offering much higher bit rates for fast internet connections.
Variable vs Constant Bit Rate
When you are encoding/exporting a video file, there is an important difference to understand: Variable Bit Rate vs Constant Bit Rate. If you choose to export with a Constant Bit Rate (CBR), your entire video will be your target bit rate, no matter what. If you choose to export at 10Mbps, every second of your video will be just that: 10Mbps.
If you choose to export with a Variable Bit Rate (VBR), your video bit rate will adjust depending on what is happening within your video. If you have a portion that has no movement or is just a black screen, the video will encode with a lower bit rate during that portion. When you export with VBR, you choose a target bit rate and a max bit rate. VBR is generally a more efficient encoding method that results in smaller file sizes.
Recording at a lower bit rate can sometimes be just what you need if you want ease of file storage and file transferring. Remember that when you’re uploading files to YouTube or Dropbox, you don’t always want massive files. Sometimes you might want to compress the file to a lower bit rate to allow for faster file transfer.
The higher the bit rate, the higher the quality of the video. The higher the bit rate, the larger the file size. Remember this! This is the reason why powerful, high bit rate cameras need special memory cards to record (SSDs and CFast cards, for example). These cameras record at such high bit rates that a standard SD card can’t record the data fast enough or will fill up too quickly.
I hope this helps shed some light on bit rate and helps you more easily choose the right camera for the right project. Examples of cameras that shoot at higher bit rates (at the time of this writing) include the Panasonic AG-CX350 4K Camcorder, the Blackmagic Pocket Cinema 4K, the Sony a6400, the Panasonic GH5, the Canon C200, and the Fuji X-H1. As you can see, higher bit rates are available in a wide variety of form factors and price points. You don’t necessarily have to spend a lot to achieve high bit rate footage, but you will need a lot of storage no matter what system you go with.