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CBR vs VBR: A Comparison Between Constant Bitrate and Variable Bitrate9 min read

August 17, 2021 7 min read

CBR vs VBR: A Comparison Between Constant Bitrate and Variable Bitrate9 min read

Reading Time: 7 minutes

CBR and VBR are two different encoding methods for video. CBR is a fixed bitrate that does not vary with the scene complexity and complexity of the video. That means it doesn’t change to accommodate more or less complex scenes. VBR uses an average bitrate that varies with the complexity of the video to provide better quality in more difficult scenes.¬†¬†There are many reasons you may want to choose one over another. This article will help you understand how they compare and which might be best suited for your needs.

This blog post explains what CBR vs VBR encoding is, their differences and comparison, and when each type of setting would be most appropriate. Before comparing them, let’s know about what CBR is and what does CBR stands for? It’s pros and cons, and then what is VBR and its pros and cons also.

What is Video Bitrate?

The Video Bitrate is the number of bits used to store one second when encoding video. It’s required to you to choose a bitrate with a bitrate control technique for encoding video the media files for streaming distribution.

CBR and VBR are two different types of encoding that correspond with how data is stored in bytes per second and defines the comparison between SD and HD. Besides, they affect the file size and quality. Video encoded using CBR generally has a high storage space but produces average quality video. In contrast, Video encoded using VBR may use less storage space, but the quality can vary depending on the content.

We can define the bitrate as the data rate or the amount of information per second the video has. It is measured in megabits per second and is directly proportional to its quality.

Generally, we tend to confuse the size of the video with its quality, thinking that the 4k size is the video that offers the highest quality. However, this is flatly incorrect.

Types of Video Bitrates

If you are one of those who want to know more about everything you study, you can stay and delve deeper with us. Video streaming is measured with the bitrate encoding process.

There are two types of data rates, the constant bitrate and the variable bitrate (VBR vs CBR).

  1. CBR
  2. VBR

Let’s dive into the blog to know more about these different bitrates.

What does CBR stand for?

It’s a frequently asked question from a vast number of people that “what is CBR?” The acronym CBR stands for Constant Bitrate. If you are streaming video or audio using CBR encoding, the data required to provide that service is set at a constant data rate.

That means whether it’s downloading a movie of less than an hour in length, watching live-streaming on any platform from TV networks to Facebook Live, or listening to podcasts and other content online while commuting or working out. Your bandwidth will not fluctuate and irrupted issues as you’re streaming due to changes in demand as every unit of time has been allocated for a specific purpose.

Pros and Cons of CBR Encoding

The first advantage of CBR encoding is that your video content will not be interrupted by buffering. It doesn’t matter how much bandwidth you have for video transcoding. In a world where data usage and broadband speeds are constantly changing, it’s important to find ways to avoid the inconvenience of dealing with low-quality or disrupted downloads.

The second advantage is that even if one has limited internet capacity, they can still enjoy their entertainment without interruption. It means people who may otherwise choose not to watch due to fear of running out of mobile data or being on WiFi can do so guilt-free! Content providers also benefit from using CBR encoding as live streaming becomes more popular since there’s less risk for decreased viewership if the audience exceeds available bandwidth.

Other advantages of CBR Video encoding:

  1. Allows a person to reliably use their bandwidth for the video content they are streaming without interruption, no matter how much data is available or what speed it’s at;
  2. There’s no risk of running out of mobile data and losing access to viewing this content as long as they have an internet connection with some remaining capacity on any device. This feature also eliminates problems when watching live streams where there might be more viewers than the available broadband can support in real-time;
  3. Content providers get increased viewership through constant quality images via CBR since there isn’t a need to resize and rescale, resulting in a lower resolution while watching.

Pros of Constant Bitrate(CBR)

  • Establish quality.
  • More control over audio quality.
  • Best for multimedia.
  • Easy to the target bitrate

Cons of Constant Bitrate (CBR)

  • It requires a connection to support it.
  • Inflexible.

What does VBR stand for?

The abbreviation VBR stands for variable bitrate. Well, the term itself suggests its functionality. All you have to do is realize the difference between the terms ‘constant’ and ‘variable.’ In other words, regular bitrate and variable bitrate are concepts with exactly opposite meanings.

VBR is an encoding method that makes the bitrate of the audio files increase or decrease according to the requirement. There is a target range when it comes to bitrate. For example, variable bitrate encoding can range from 65 kbps to 320 kbps. VBR supports audio file formats like MP3, WMA, and various other formats.

VBR file formats have the unique feature of sound quality and file size ratio. That’s the most significant advantage associated with VBR files when compared to CBR. That’s why, for matching the quality of the video file, a user can achieve a smaller file size.

For example, if the original sound quality of the file is relatively low, VBR will alter the size of the file. Thus, low-quality files will be lightweight, and the exact opposite will be true for high-quality files. Based on the VBR mechanism, the file bitrate will be noticeably lowered for inaudible segments. What about the more complex parts of the track (where there is a mix of frequencies)? Well, the bitrate of those segments will automatically increase to a maximum of 320 kbps.

Therefore, the sound quality will be maintained in the areas where it is necessary. So overall, this is a great way to achieve a reasonably small file capacity while maintaining decent quality. In general, you will need less space to store VBR files instead of CBR.

Pros and Cons of VBR encoding

VBR allows the bitrate of an audio file to increase or decrease within a target range dynamically. The LAME encoder, for example, ranges from 65 Kbps to 320 Kbps. Like CBR, audio formats like MP3, WMA, and OGG support VBR.

The most significant advantage of VBR encoding compared to CBR is the ratio of sound quality to file size. Smaller file size can usually be achieved by encoding the audio with VBR rather than CBR due to how the bit rate is altered depending on the nature of the sound.

The bit rate is reduced for silence or quieter parts of a song. For more complex areas of the music containing a mix of frequencies, the bit rate increases up to 320 Kbps to maintain sound quality. This variation in bit rate reduces the required storage space compared to CBR.

However, the downside of VBR encoded files is that they may not be compatible with older electronic devices such as CBR. It also takes longer for VBR encoding audio because the process is more complex.

Pros of Variable bitrate

  • Smaller file size.
  • Flexible bit-rate reduction.
  • More efficient in many situations.

Cons of Variable bitrate

  • Possible decreases in quality.
  • Less support.
  • More coding time.

CBR VS. VBR Which is Better Quality? Which Should I Pick?

The use of one or the other method depends fundamentally on two factors that cannot be analyzed separately since they are co-dependent:

  • The intended quality
  • The available capacity

Let’s say we will compile video onto a double-layer DVD with a capacity of 8.5 GB. The video clips are in HD resolution(720p), and although the figures that will be used for the example cannot be precise because they depend on the type of compression used, we are going to assume that in total, putting all the clips together, we add up to 10 minutes.

The result of the compilation carried out in VBR encoding to the standard commonly used for this quality (6-8 Mbit/s) would only be occupying 0.7GB of the total disk capacity. Then, according to our capacity budget, we can still increase the bit rate to increase the amount of information. Besides, we can also increase consequently the quality of the image.

In this specific case, we could use the CBR mode at the maximum quality that the software/hardware that we are using allows us and increase the bit rate, for example, to 9 Mbit/s, thus maintaining constant good quality at all times of the film without any risk that the disc is not enough to record the total 10 minutes.

Going back to the example, let’s now suppose that instead of 10 minutes, our clips total 90 minutes. In advance, we know that the 8.5GB disk will not hold that amount of information at the highest consistent quality, and that is when we use the VBR encoding mode to carry out the compilation. As a stream user, you should have a clear knowledge of the bitrate control technique.

CBR vs VBR: Which Encoder Does Castr.io Recommend for Live Streaming?

Castr.io– one of the best video multistreaming software, recommends using constant bitrate(CBR) for max bitrate. Because it allows you to adjust video quality based on what is happening in your video feed. CBR also produces higher-quality streams than VBR, making them ideal for large audiences that consume live content online like sports games or concerts.

But you can also try VBR for live broadcasting on our streaming platforms. Experience both encoders and choose what is congenial to you.

Conclusion

CBR is a more reliable way to stream your video content, but you can also use VBR if needed. It’s up to you which one is better for your specific needs! Castr.io focuses on giving high-quality videos with low bandwidth usage. So, we recommend that all startups go ahead with CBR for their streams instead of VBD or any other variant.

As long as there are no major changes in technology over the next few years, we expect all live streaming platforms to be using this format due to its reliability and a generous allowance for infrastructure upgrades. The biggest difference between VBR and CBR is that VBR allows you to adjust the video quality based on what’s happening in your feed. So, if there are any changes in your content or live streaming technology, this will allow for a more flexible give and take.

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