Bit Rate Explained

This guide will give a deeper understanding of bit rates and their overall impact on the performance of surveillance devices.

 

What Does Bit Rate Mean?

A bit rate in video is essentially the amount of data that's being used and sent for that particular stream.  Another simple way to think of it is bit rate is the quality of the video.  More data means better quality video, but not without limitations.  While there's a much more technical definition available online the above sentences should sum it up into something easily digestible for most.

Bit rates are, as of this writing, represented by a Kilobits per second number or "kbps".   For example, 256, 512, 1024, 2048, 4096 and up.  Those specific values do not have to be used however and can often be adjusted higher or lower as needed.

 

Bit Rate Location:

The majority of surveillance products on the market allow adjustments to be made on many settings within the camera or recorder.  Bit rate is no exception and is often found under the device configuration page and is labeled Video/Audio or something similar.  Conversely, some devices on the market do not allow adjustments to the bit rate.

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Bit Rate Type:

There are two main bit rate types that can be selected, VBR and CBR. 

VBR stands for Variable Bit Rate, which means the bit rate will fluctuate in value depending on whats happening in the scene with more activity/movement leading to a higher value and less activity leading to a lower, more stable value.  When adjusting the bit rate value with VBR selected it's often setting the highest (Max. bit rate) it will go to while it dynamically adjusts.

CBR stands for Constant Bit Rate, which means the bit rate value (Max. bit rate) will stay the same regardless of what's happening in the scene.  The value will not fluctuate higher or lower from the value currently set on the device.  This can be positive for certain scenarios where consistent quality is an absolute requirement but can also have a negative impact on the total storage/days of video available due to the extra data constantly being used and in some cases the extra consumption of bandwidth as well.

 

Resolution/Bit Rate Synchronization:

When most people hear the word "quality" or "high definition" they think of the resolution of video (720p, 1080p, 4K, etc) and they aren't wrong however even with high resolution video an incorrect bit rate value can make the image quality pixelated and ultimately useless as a form of evidence.   There are numerous standard definition (SD) and high definition (HD) resolutions available to choose from on most surveillance cameras and each resolution has a corresponding bit rate "sweet spot" that isn't a really high or really low value.  Corresponding both resolution and bit rate values ultimately provides good performance and good quality video all while avoiding any potential problems.  Keep reading for our recommended bit rates for most resolutions currently available.

 

Bit Rate (Mis)configurations:

Users often configure bit rate values to high or to low.  This can have a detrimental impact on surveillance systems as well as the quality of the image.  Each scenario is different but most of the negative results are due to exceeding bandwidth limitations of the recorder and using unnecessary bandwidth (too high) or major pixelization of the video if set to low. 

Bit Rate To High

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The "No Resource" error displays on a Hikvision NVR which is often caused by exceeding the bandwidth limitations due to an abnormally high bit rate set on one or more cameras.

 

Bit Rate To Low (click to view full size image)

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A pixelated 4K IP camera with a bit rate value set at 256kbps.

Most cameras are configured with a default bit rate which is often a good value in between performance and quality.  For most scenarios the bit rate does not need to be adjusted as the default values provide adequate video quality right out of the box.  In addition, by adjusting the default values you increase the likelihood of causing certain problems such as the ones shown above or others.

Hopefully this guide has provided a better understanding of what bit rate is and the impact it can have.  If you think venturing away from the default value could be beneficial to your scenario but still aren't exactly sure what value to use you can find our recommended camera resolutions and corresponding bit rate values on this page.

Here's a quick recap of everything:

1. Bit rates are essentially the quality of the video and are represented as a number value.

2. Most surveillance systems allow adjustments to be made to that value and are usually located in the devices configuration. 

3. The bit rate value is often accompanied by either a Variable Bit Rate (VBR) or Constant Bit Rate (CBR) setting. 

4. The resolution of the video should always correspond with the bit rate value.

5. Setting the bit rate value to high or low can have a negative impact on the video quality, bandwidth and operation of the recorder. 

6. The default values usually don't need to be changed because they provide a good middle ground between overall performance and quality of video.

7. Our recommended bit rates for the majority of currently available resolutions can be found here.

                                                                                                                                                       

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