Standard definition (SD) and High definition (HD) systems that run over coaxial cable have already had their cameras measured by frame rate.  Once we understood what it was, it provided us with a good idea of what kind of capabilities a camera may have.  Network camera, or IP cameras, are measured differently; instead of a frame rate, IP cameras depend on bandwidth.   These types of cameras can still have their frame rates limited to certain numbers, but it’s really going to come down to what the bandwidth requirement for that camera is, and what the video recorder (NVR) is capable of supporting.

Frame Rate vs. Bandwidth

Frames rates still apply and translate with IP cameras, but instead of just looking up the max frame rate on the spec sheet, finding an IP camera’s potential frame rate involves a little more math.  Each resolution records at range of available bitrates.  The higher the bitrate, the higher the quality.  Each Resolution also has a maximum bitrate that it can’t exceed.  Your SD and HD analog cameras are identical when it comes to this, but these bitrates play a much larger role with IP cameras.  At 2 megapixels, your IP camera will require a bitrate of around 10,000 Kb/s to record at it’s highest quality; this is the camera’s bandwidth requirement at this resolution.  While this doesn't tell you how many frames per second you’re going to get, it get’s you headed in the right direction of finding out.  The other determining factors will be the bandwidth requirements of the the remaining cameras is the system, and the big one will be the incoming bandwidth on your Network Video Recorder (NVR).


Incoming Bandwidth

The amount of incoming bandwidth your NVR is working with is printed right up front for you on the spec sheet.  While your security cameras are measured in kilobits per second (Kb/s), your NVR’s incoming bandwidth will likely be measured in megabits per second (Mb/s); the conversion is simple enough.  An incoming bandwidth of 80 Mb/s is pretty standard among smaller standalone NVRs.  Converted to camera terminology, this means the NVR has 80,000 Kb/s of usable bandwidth on that NVR.  If your 2 megapixel cameras are using 10.000 Kb/s apiece, then you’ll be able to have as many as eight of them, while maintaining those cameras’ highest recording capabilities.  Whether the highest available frame rate of your camera is 20fps or 30fps, you’ll be able to achieve that in this scenario.  However, if your NVR allowed for it and you were to exceed eight cameras on the recorder, you would no longer be able to record at the maximum number of frames per second on all camera anymore.  Your options at this time would be to attempt slowly lowering the bitrate to accommodate for the extra camera, or to simply lower the frame rate on some or all cameras so that your system once again meets the bandwidth requirements.

Lowering the Bitrate

Lowering the bitrate can sometimes be your solution if you find yourself in need of one.  Lowering the bitrate of your cameras will mean lowering the amount of bandwidth they require, but as we've made clear, this is linked to the camera’s picture.  By lowering the bitrate at which the camera’s recording at, you’re also reducing that camera’s image quality.  In small doses, reducing these bitrates can solve your issue, and the degradation in image quality can potentially go unnoticed.  In other cases, you might find that something more extreme is needed to avoid neutering your high definition picture.

Lowering the Frame Rate

In cases where reducing the bitrate wasn’t a viable option, reducing the number of frames per second at which the camera is recording is your last option.  A full 30fps has become what the vast majority of the market has come to expect because of how much more mainstream it has gotten in the CCTV industry over the last few years.  For even mid-sized IP camera systems, this can sometimes be hard to achieve; this is, of course, all related to available bandwidth.  While lowering the frame rate might not seem like a lot of fun, the good news is that most people don’t realize how absurd it usually is to be recording all of those frames.  In a lot of instances, you’ll find that recording at even just 7fps is enough to capture almost anything moving at a standard rate of speed.  Unless you’re looking for an extraordinary amount of detail in a quickly moving object, there is nothing wrong with recording at 1 to 15 frames per second.

Don Stephens is a Technical Support Manager at CCTV Camera World, a leading Security Camera distributor located in Buffalo, NY. His area of expertise is in designing professional security camera systems for medium and large scale businesses, schools, and government projects.

Connect with Don via: Email  |  YouTube