What is Bit Rate?

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  • Written By: Alex Paul
  • Edited By: R. Halprin
  • Last Modified Date: 15 October 2019
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Bit rate measures the speed that information can be transferred between two locations. The standard unit of this rate is “bits per second,” but this is often prefixed with kilo- or mega- to recognize the high rates found in modern digital technology. Communications technology measures speed by bit rate, especially on the Internet, where the rate of transfer provides an insight into how quickly data can be downloaded. This measurement is also commonly used to describe audio and video; higher rates signify greater quality.

At its most basic level, bit rate describes how many bits are transferred between two different locations per second. The higher the rate, the faster information can be communicated between them. For this reason, bit rate can be especially important for communications technology such as broadband because it defines how quickly a user can download or upload information.

The standard unit of bit rate is “bits per second” (bps). This measurement is usually far too small to be practical in modern communications technology, however, because millions of bits can be communicated every second. To get around this problem, the unit is often prefixed with another letter denoting its size. Kbps, for example, stands for kilobits per second or thousand bits per second. Megabits per second is written as Mbps and stands for million bits per second.


Bit rate is an important measurement in a variety of different computing fields. Broadband, for example, is often quoted as having a certain number of Mbps, with speeds of about 2 Mpbs being common. Fiber optic broadband, which is much faster, can offer speeds of up to 5 Mbps. This measurement also describes the speed of mobile connectivity such as 3G and Bluetooth.

Audio and video quality is commonly written in terms of bit rate, with higher rates signifying greater picture or sound quality. In multimedia, this measurement is a quick way of showing how much information is stored within each second of recording, which is why higher rates result in increased quality. The bit rate can depend on a variety of factors including whether the information has been compressed.

The standard bit rate for audio is between 100 and 160 kbps, while the highest quality recordings may go up to 320 kbps. Video rates can be considerably higher than this, with Blu-ray discs capable of up to 40 Mbps. Standard DVDs only have a rate of about 9 Mbps, which is why there is such a noticeable difference in quality.


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Post 3

While this is a good introduction, I 'd like to point out that video quality is not only affected by bit rate but frame rate as well. Frame rate is how many frames per second of video is captured.

For example, most camcorders will, by default, capture video at 60 frames per second. That's the default on my camcorder, but I can adjust this higher or lower as I need to.

Frame rates will affect the motion quality of the video. The higher the frame rate, the smoother the motion, and vice- versa.

Bit rates refer to how much information you’re pushing into each frame. Therefore it affects the quality of the image in each frame. Like

frame rate, the higher this number the better it is. However, with more information comes increased file size.

So it comes down to a tradeoff. You can adjust both bit rates and frame rates, as you will, but it will affect image quality and motion, accordingly.

Post 2

@m3g4n – The constant bit rate setting will always try to push the same number of bits to your computer each second. The variable bit rate setting will allow the software to choose the bit rate dynamically.

When given the choice, I always choose the variable bit rate setting when I play games online. The game itself keeps track of how much bandwidth it is using, and it will change bit rates accordingly.

I noticed that when I used a constant bit rate for the game’s audio, the game would start lagging when I entered a graphics intensive area. That’s because the graphics were taking up a lot of my connection’s bandwidth, but the audio kept streaming at the

same rate, and together they ate up all my bandwidth.

The game hardly ever lags when I’m using the variable bit rate audio setting. I can enter the same graphics intensive area, but the game software notices that the graphics are eating up a lot of bandwidth, and it will lower the audio bit rate accordingly.

Post 1

Okay, so what’s variable bit rate? An online game I play has the option of having the game audio sent at variable or constant bit rate. Which one should I pick? I don’t know anything about either one.

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