The demand for video content is increasing at a considerable rate. An average viewer spends around 17 hours per week watching online videos, and around 91% of businesses are using video marketing.
As video platforms experience sustained growth, and high-resolution video becomes the dominant way to consume content on the internet, it becomes crucial to provide viewers with a seamless experience for the same. To do that, you must understand video bitrate properly.
The aim of this article is to give you a detailed look at video bitrate and help you choose the perfect bitrate depending on your content and use case.
Let’s dive right in.
What is Video Bitrate?
Video bitrate is the amount of video data processed and sent in a given amount of time. It is usually measured in bits per second, representing the amount of data (in bits) that is encoded for each second of video playback.
A higher video bitrate means that more data is being encoded per second of video, which results in higher video quality with more detail.
Video Bitrate vs. Video Resolution
Video bitrate is often confused with video resolution terms like 720p, 1080p, 4K, etc. and this is mostly because the average person is more familiar with the latter – resolution alone is what consumer equipment like TVs and monitors have on the cover, after all.
And a higher resolution will always mean better quality, right? Bigger numbers are better, more pixels should always mean sharper, more detailed visuals? Not exactly.
Think of video resolution as the number of tiny dots that make up the picture you see on the screen. More dots should mean a clearer and more detailed picture, but a higher number of dots isn’t everything. Each of these dots needs more information – to be shown at the right color, position, and more. Video bitrate is like the amount of this ‘information’ allotted for each dot. A higher bitrate means each dot gets more data, and as a result, the video has better quality, with less blurriness or pixelation.
This is not a linear relationship. It's possible to have a low-resolution video with a very high encoding bitrate, which would technically result in a high-quality video with more data per pixel, but the overall sharpness and clarity might still be limited by the low number of pixels.
The reverse is actually more commonly true – especially for video streaming platforms. How many times have you heard complaints that a YouTube video is a blurry mess of pixels, even at the highest resolution, 4K? The cause of this is a low bitrate, of course.
The Two Types of Video Bitrate
There are two different strategies used in video encoding, to control the amount of data used to represent the video.
They are:
- Constant Bitrate (CBR)
- Variable Bitrate (VBR)
Constant Bitrate (CBR)
Constant Bitrate, as the name suggests, maintains a fixed bitrate throughout the entirety of the video, regardless of the complexity of the scene, or the amount of motion in it. Every frame of a CBR-encoded video receives an equal share of the total bitrate, no matter what.
As the same amount of bitrate is maintained across the stream, the resulting file sizes and bandwidth demands are consistent and easy to predict. For this reason, it has wide use in live streaming.
A steady data flow is important for an uninterrupted live stream, and these platforms catering to user-generated content need to fit videos within a specific (and frequently limited) storage capacity or transmission bandwidth.
Even though it may sound like CBR is the most reliable strategy for all use cases, that’s not always true. With CBR, a simple, mostly static scene may not need that much detail, yet it’ll be allocated too much data regardless, for very little (or even placebo) gains in image quality.
On the other hand, complex scenes in the same video file with lots of motion or detail may be bitrate starved, leading to a blurry, pixelated mess and ultimately a worse viewing experience overall.
Variable Bitrate or VBR
In contrast to CBR, VBR or Variable Bitrate adjusts the bitrate dynamically depending on the complexity of the video. Overall, it can deliver a higher perceived video quality compared to CBR for the same file size because it allocates more data to parts of the video that require it the most, avoiding wasteful allocation of data in simple scenes and ensuring high-quality representation in complex scenes.
Variable Bitrate encoding makes for an ideal choice for streaming pre-recorded videos because these often contain a mix of scenes, some with high complexity (e.g., action sequences, detailed visuals) and others with lower complexity (e.g., static shots, simple scenes).
VBR adapts the bitrate to match the content, ensuring that these parts of the video retain more details, colors, and motion clarity. As a result, viewers are less likely to encounter abrupt quality changes between scenes and experience fewer visual artifacts.
However, even VBR has its drawbacks. VBR encoding is more computationally intensive than CBR encoding. The process of analyzing the video content to dynamically allocate bitrates to different scenes, requires more processing power and time, meaning longer encoding times.
So, on older or less capable devices, CBR might be more compatible (or easier to handle from a performance standpoint) than VBR.
For the same reason, time-sensitive content like low-latency live streaming, would benefit more from CBR, instead.
Now that you have a basic understanding of what video bitrate is and the different types of it, let's explore more on what factors influence the video bitrate.
Factors that Influence Video Bitrate
There are many factors that influence the choice of bitrate, such as video resolution, frame rates, codecs, file compression, etc. Let’s discuss the roles of each on video bitrate, one by one.
Video Resolution
The resolution of the video, represented by the number of pixels in width and height (e.g., 1920x1080 for 1080p or “Full HD”, and 3840x2160 for 2160p or “4K”), directly affects the bitrate. When going to higher resolutions, such as making the jump from 1080p to 4K, for example, you’ll have more pixels to display, and therefore require a higher bitrate to represent motion, color, etc. for those increased number of pixels properly, or suffer a lower image quality.
For example, Google recommends a bitrate of around ~8,000 Kbps or 8 Mb/s to represent 1080p Full HD video at standard framerates encoded with the H.264 codec, but recommends 35,000–45,000 Kbps or ~35-45Mb/s to represent the same video, at the exact same settings, but at 4K, more than quadrupling bitrate requirements.
Frame Rate(FPS)
Video is a collection of still images, or “frames”, displayed several times per second, creating the illusion of motion. Frame rate is the frequency at which these consecutive frames appear on a display. It's typically measured in frames per second or FPS.
A higher frame rate creates a smoother video, simply because more images are displayed each second. A video at 60 FPS shows a new frame every 1/60th of a second, while a video at 24 FPS presents a new frame every 1/24th of a second. Thus, a video at 60 FPS needs to show more than twice the amount of frames in the same time frame, compared to a 24 FPS video, meaning a steeper bitrate requirement.
For example, for a 1080p video, Google recommends a bitrate of 8 Mb/s for standard frame rates (24/25/30), but 12 Mb/s for the same video at high frame rates (48/50/60)
As a rule of thumb, higher frame rates lead to increased data that needs encoding, resulting in larger file sizes and higher bitrates for the same quality per frame. Conversely, lower frame rates like 24 or 30 FPS require less data encoding per second, leading to smaller file sizes and lower bitrates while maintaining the same quality per frame.
Lower frame rates can be more efficient for delivering videos over limited bandwidth networks, though the trade-off, in that case, would be decreased smoothness of motion – “choppy” playback.
Codecs
A codec is a program that encodes or decodes a digital data stream or signal. These codecs compress the raw video data into a format easier to transmit and store, then decompress it for playback. Different types of codecs handle this compression and decompression process in varying ways.
An efficient codec can deliver high-quality video at lower bitrates. A great example of this is the H.265 (HEVC, or High Efficiency Video Encoding) codec, part of the MPEG-H spec. Made by the creators of H.264, H.265 is far more efficient, boasting compression that allows for the same visual fidelity at just half of H.264’s bitrate.
Video Compression
While all codecs compress raw video data, not all compression techniques are created equal, even for the same codec. Video compression can be further categorized into two main types: lossy and lossless, and each type has a significant impact on the resulting video bitrate.
Lossy Video Compression
It involves removing some non-essential video data to achieve higher compression rates. It works by removing redundancies and details in the video that won’t immediately be visible to the naked eye. Even within lossy compression, codecs come with presets – a set of pre-defined configurations that determine the trade-off between encoding speed, compression efficiency, and video quality.
Lossless Video Compression, on the other hand, retains all the original video data without any loss in quality, resulting in larger file sizes and higher bitrates compared to lossy compression.
Now that you clearly understand the factors involved in providing excellent video quality and streaming experience let’s discuss how the bitrate can be calculated.
How to Calculate Video Bitrate
Calculating the optimal video bitrate you’ll need is quite simple if you know the file size and the length of the video content. You can easily calculate the bitrate in either Megabits per second or Kilobits per second.
The formula for calculating video bitrate is:
What’s the frame size? Well, that’s given by the formula:
Where:
- Resolution is the width multiplied by the height, in pixels
- Bit depth is the number of bits used to represent the color of each pixel (e.g. the standard 8-bit colorspace, or 10-bit)
This means that with no compression, here’s the minimum bitrate you’d need to accurately represent:
1) 1080P video at 30FPS at the standard 8-bit color depth (for each channel, R, G, and B)
1920 * 1080 * (8 * 3) * 30 = 1492992000 Bits per second, or ~1500 MBit/s
2) 4K Video at 60 FPS at the typical 10-bit colorspace high-end videos use
3840 * 2160 * (10 * 3) * 60 = 14929920000 Bits per second, or ~15000 Mbit/s
These will lead to massive file sizes – ~1500 MBits, or ~187.5 MegaBytes of video data per second just to represent 1080p video at 30 FPS, and that’s not even considering the audio channel (multiply the final result by 2 for stereo audio)!
Now you see why video encoding, compression, and codecs which do it, are essential in the world of video.
What Bitrate Should You Use?
It’s obvious that raw video data is just not practical for any transmission media – be it streaming, or home video. But even with modern codecs, relying only on arbitrarily high bitrates will create large file sizes and require more bandwidth for data transfer, and we’re back to square one, especially for users with slower internet connections.
It’s clear that finding a balance between the video bitrate and the video resolution is vital to ensure an optimal viewing experience. So let’s discuss which bitrate you should choose depending on the quality of the content.
First of all, there is no one-size-fits-all choice for bitrate. Depending on the target audience, the platform of the stream, the content itself and the complexity of its scenes, and the available bandwidth, video bitrates will vary. Even though high-quality videos should theoretically provide a great visual experience to the users, they might not be the best viewing experience for users because
- The video platform might not even use most of the high bitrate you’re throwing at it. Netflix, for example, uses a bitrate of only about 20 Mbit/s for 4K video at 24 FPS, at the time of this blog post.
- Your content might not even need bitrates that high, so you're just wasting processing power and bandwidth.
- Viewers on lower bandwidth connections or lower-powered devices might not even be able to play your high-bitrate video.
And of course, all issues at the other end of the spectrum apply to bitrates that are too low, too.
So let’s discuss a step-by-step guide to help you choose the most optimal video bitrate given a specific use case.
Step 1. Understand Your Platform
The ideal approach for choosing the optimal bitrate should be to start with a baseline bitrate for a given resolution, and then adjust according to different factors. Where do you begin, though? The obvious choice would be the platform you’re on.
Different video formats and platforms have specific requirements and recommendations for video bitrate. For example, streaming platforms like YouTube, Vimeo, or Twitch often provide guidelines for optimal bitrates based on resolution and frame rate. It's essential to review the recommended bitrates for the chosen format and platform to ensure compatibility and optimal viewing experience.
For example, to upload your videos to YouTube, you should follow their guidelines for choosing the optimal source bitrate according to the table below:
As the setting for 1080p standard frame rate video mostly correlates between YouTube, enterprise streaming platforms like IBM, and Facebook Live – let’s go with this as a baseline, taking a bitrate of ~8000 Kbit/s or ~8 Mbit/s as our starting point.
Step 2. Understand Your Content
If your content is fast-paced action, intricate details, or high-resolution visuals (e.g., gaming videos, sports events, or high-quality animations) you’ll need higher bitrates to preserve visual clarity and prevent compression artifacts. Conversely, less complex content (e.g., talking-head interviews or static images) may be adequately represented with lower bitrates.
This is also where the advantage of VBR becomes apparent. Video content is rarely 100% one or the other – you’ll frequently have varying content types and scene complexities within a single video (sequences with both busy, action-packed scenes and static shots). VBR is a must-use for these scenarios, allowing for efficient allocation of bitrates, ensuring that both the high-action sequences and the simpler scenes receive an appropriate amount of data – not merely equal shares – for optimal representation.
Let’s take the high end of the spectrum first, and adjust accordingly. Starting from our baseline above (8 Mbit/s for 1080p at standard frame rates), a suitable starting point for VBR encoding of 1080p video at 30 fps could be a target bitrate between 10 to 20 Mbps. This range provides a good balance between video quality and file size.
Now, if most of your video content is very fast motion or high-detail content, consider going even higher, up to 30 Mbps or more. If you’re sure it’s mostly static content like interviews, go back to the baseline (~8 Mbps).
Step 3. Understand Your Audience
Understanding the preferences and expectations of the target audience is a crucial factor in determining the ideal video bitrate. Different audiences have different viewing habits, and that can influence the choice of bitrate to ensure an optimal viewing experience.
For example, if you’re uploading a portfolio for potential connections in the film industry, they will expect top-notch video quality with minimal compression artifacts – and that’s where you go for the highest bitrate you can afford – while casual viewers of user-generated content (think Instagram/Facebook Live, social media uploads, etc.) might be more forgiving of some quality trade-offs in exchange for faster streaming – and for these audiences, you could stick to the platform baseline, or go lower if you feel the content is going to be brief enough to not care.
And that’s not all. Regional internet speeds and device usage can all influence the audience's tolerance for video quality and bitrate. It’ll never be a one-size-fits-all approach, you’ll have to make adjustments as and when required, and that’s why knowing your audience is so important.
Step 4. Monitor, Adjust, Repeat
Based on the above steps, keep testing and adjusting your videos to get the perfect mix. Also, be open to feedback. If viewers are experiencing issues like buffering or low quality, you may need to adjust your bitrate or other settings. Regularly assessing audience feedback and adapting bitrate settings based on their preference is advised.
Keeping these in mind can help you choose the perfect bitrate for your content.
How ImageKit Can Help You with Video Bitrate Conversion and Optimization
It is crucial to choose the right tool when it comes to bitrate conversion and optimization. To reduce the stress of manual video optimization, and bitrate conversion, ImageKit can be a great tool. It is a cloud-based modern media stack – a Digital Asset Management platform, video optimization, and transformation service, all in one – that can make sure you deliver videos at the most optimal bitrates every time, no matter which device you’re creating content for.
Automatic video quality optimization
ImageKit can optimize your videos automatically, using the latest in video transcoding and compression technology to strike the perfect balance between file size and visual fidelity every time.
No encoding software or infrastructure needs to be set up on your part, all you have to do is turn on Automatic Quality Optimization from your ImageKit dashboard.
While this is a good enough default, you can adjust this further if you wish to – with the ‘Default quality’ setting that goes from 1 to 100, representing a sliding scale where 1 prioritizes lower file sizes at the expense of image quality, and 100 represents the opposite.
Adaptive Bitrate Streaming
Adaptive Bitrate (ABR) streaming, like VBR encoding, is another solution for adjusting bitrate dynamically as needed to optimize video quality and efficiently use data – with just one crucial difference.
While VBR is a video encoding technique that varies the bitrate during the video creation process based on scene complexity, ABR is a video delivery method that involves creating different quality variants or “renditions” – which are segmented into smaller chunks or segments, and the client side player dynamically switches between different bitrate renditions during video playback to adapt to changing network conditions.
ABR is incredibly helpful, but setting it up is difficult. ImageKit makes this process painless, letting you generate and request adaptive streaming versions of a source video with its URL-based API. Renditions and manifest files are generated for you automatically – and all you’ll have to do is embed a single URL in an ABR-compatible, HTML5-based video player client side.
ImageKit ships with these features out of the box, meaning you’ll be able to provide your users with the best possible video streaming experience without worrying about what bitrate to choose, or what resolution would be the best for your viewers. Just upload one source video to ImageKit, store it in its Media Library, and let ImageKit optimize it on delivery – and at scale, too.
Conclusion
In this blog post, you discovered what video bitrate is, its types, and how it differs from video resolution. You also learned the different factors that influence video bitrates – and why racing after higher and higher resolutions alone is not the right answer.
You’ve also learned about how variable bitrate encoding (VBR) and adaptive bitrate streaming (ABR) play vital roles in bitrate optimization, and the significance of understanding the platform, the content, and the audience in choosing an optimal bitrate – and how ImageKit helps you deliver bitrate-optimized videos at scale.
If you are someone who is serious about providing an exceptional video experience to your users without worrying about the complexities of manual video bitrate optimization, Try ImageKit for free today, with 20GB of free media storage and video processing on us.