Considering Bandwidth

A reason why IP cameras are gaining in popularity is because network infrastructures are constantly growing in size and capabilities as are internet speeds.  Just like uploading and downloading images or video to and from the internet, speed plays a crucial role in the quality of our experience. 

The same goes for accessing stored data or live images from our computer’s network or accessing them remotely via the internet.

It is a common misconception that video surveillance systems consume vast amounts of bandwidth. Unlike downloading video from the internet, streaming IP video over a network generally does not eat up much bandwidth.

Video Compression

Were it not for compression formats known as codec (coding-decoding), digitized video which consumes hundreds of Mbps (mega bits per second) worth of bandwidth, would not be practical to transmit over an IP based network and would be costly in terms of amount of space required to store the data. So, various compression formats have been developed to reduce large amounts of redundant information.

Video Compression Formats

The most common video compression formats used today are:

  • Motion JPEG (M-JPEG):  Represented as a series of of JPEG images.
  • MPEG-4:  The next generation of MPEG (Moving Picture Experts Group) that supports low-bandwidth consuming applications (such as cell phones) and applications that require high quality images and with virtually unlimited bandwidth.
  • H.264:  The latest standard for video encoding that provides good video at low bit rates.

Many IP cameras are designed to handle multiple compression formats for different applications such as the MPcam MPF-7018 with individually configurable video streams in JPEG, MPEG-4 format.  

Variable and Constant Bit Rate

Another important aspect of compression formats is the bit rate used and oftentimes it is possible to select the rate:  constant bit rate (CBR) or variable bit rate (VBR).  Bit rate is simply the rate (in a given amount of time) at which bits (data) are transferred from one location to another.

With limited bandwidth the preferred mode is CBR because this mode generates a constant and predefined bit rate.  The downside is that the image quality will vary depending on the amount of motion in the video scene.  No motion = high image quality.  Increased motion = low image quality (the more movement in a scene, the more data being transferred).

When there is a need for high quality images and the network infrastructure has a high capacity, VBR is the desired bit rate.  When there is motion in a scene image quality can be maintained because the bit rate is allowed to vary to achieve this high quality and because the network has the available bandwidth to handle it.

Network Design Considerations

Depending on the level of quality you’re looking to get out of your surveillance system, different compression standards and configuration can and should be considered.  No single standard fits all solutions.

  • Frame Rate: 
    • What’s the required frame rate? 
      • Below 5 fps Motion JPEG is a good choice and can be controlled by video motion detection on the camera. 
      • For higher frame rates MPEG-4 is best for it’s bandwidth and storage saving ability.
  • Bandwidth: 
    • What’s the available network bandwidth? 
      • Consider CBR vs. VBR and remember that image quality may suffer when there is motion.
  • Image Quality
    • What’s the acceptable level of image degradation allowed for your application?
      • Compression ratios above 90% can be used if the scene is not terribly complex.
  • Latency:
    • How much latency (time) for the compression process is allowed?
      • Point, Tilt & Zoom, (PTZ),  IP Cameras need low latency for their live images but, if video is only recorded latency may not be an issue, check the camera specs out before you buy.
  • Robustness: 
    • How robust/secure must your system be and what is your budget for this system?
      • A camera is only an added security feature for the property or target area you are trying to protect. As with any security device it needs to be monitored and should be linked to other security devices to increase your protection strength. As the saying goes if a tree falls in the forest will it make a noise? Of course but if your not there to hear it does it matter, same goes with security, if your not there to see the breach, it does it matter.
    • Is it acceptable for video to be lost for X amount of seconds if the network drops a frame?
      • Well this depends on what your looking for, some of you may not want to loose any data, whereas other are simply looking for a device to watch areas for them, to give them piece of mind. This is purely up to the buyer and depends on their required situation for purchasing a camera. When in doubt check out the camera specs.
  • Standard & Compatibility
    • Is your system compatible with other systems and is it important for ease of use in what you’re looking for?
      • Most if not all IP cameras are compatible for all applications, there may be some tweaking required depending on your operating system and platform used.
      • If ease of use is the issue, then IP cameras are the product for you, s they often promote ease of use, easy do it yourself (DIY)
      • Be certain you choose a product which meets your standards and requirements and you will not be disappointed.

Calculating Required Bandwidth

If you need or insist on calculating network requirements for a video surveillance system, you need to do the following.

  • Determine your complete viewing area.
  • Determine your recording needs.
  • In addition you need to:
    • Determine the quantity of cameras needed.
    • What type of compression is required.
    • And what resolution and frame rates you will need. 

It’s no big deal, at any one time most of your devices will be viewing and not recording and transmitting, they will be viewing, recording and saving. Bandwidth will only be used when you connect to your device from an outside source and then again the amount of bandwidth you use will be redundant.

Conclusion

If bandwidth proves to be an issue, then consider recording and storing your video locally.

Some cameras now feature a built in Micro SD/SDHC card slot for storing video clips and images, but do you want to be swapping out cards or overwriting the data.  While others send the information to a dedicated storage device, such as a computer, laptop or external storage drive.

Your camera can do what you want it to do, but it depends on the specifics requirements of the surveillance site; you can also reduce bandwidth consumption by reducing frame rate and image quality or altering the recording schedule.

In short, IP video often does not consume as much bandwidth as it is often assumed to do.

Contact us today and speak with one of our sales experts, they are more than willing to help you develop a camera (video surveillance) system for you; which will not drain your resources.

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