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We Know CCTV – But Everything You Need to Know

CCTV

We hope this book helps educate you, making you better at Selecting and using video surveillance system and About CCTV – Everything You Need to Know.

CCTV stands for closed-circuit television and is commonly known as video surveillance. “Closed-circuit” means broadcasts are usually transmitted to a limited (closed) number of monitors, unlike “regular” TV, which is broadcast to the public at large. CCTV networks are commonly used to detect and deter criminal activities, and record traffic infractions, but they have other uses.

CCTV technology was first developed in 1942 by German scientists to monitor the launch of V2 rockets. It was later used by American scientists during the testing of the atomic bomb.

CCTV Resolution

The most notable shift in camera is resolution and 1080p is highly required by most of us. Since the beginning of 1080p Resolution, there is significant drop in lower resolution cameras.

Understanding video surveillance resolution can be surprisingly difficult

and complex.

Seeing Details

camera resolution was measured with line counts, literally the camera’s

ability to display more lines side by side in a given area on a monitor. If you could see more lines, it meant you could see more real world details

– facial features, characters, license plates, etc.

720p cameras to be roughly equal to 500 ‘lines’, 1080p roughly 900

‘lines’, etc.

Pixel Count

Resolution has been redefined as counting the number of physical

pixels that an image sensor has. For example, a 1080p resolution camera is commonly described as having 2MP (million pixel) resolution because the sensor used has ~2 million pixels on it (technically usually 2,073,600 pixels as that is the product of 1920 horizontal x 1080 vertical pixels).

Pixels are a necessary, but not sufficient, factor for capturing details.

Sensor vs. Stream

Cameras with maximum resolution sensor still has less stream sent. Panoramic cameras where a 5MP sensor may be used but only a 2MP max output stream is available.

Make sure to check not only the resolution of the sensor but the stream

resolutions supported and used.

Compression

Each pixel is assigned a value to represent its color, 1080p/30fps stream would more typically be recorded at 1Mb/s to 8Mb/s – 1/100th to 1/1000th less than the uncompressed stream.

H.264

H.264 is a video compression technology, or codec. As a video codec, H.264 can be incorporated into multiple container formats, and is frequently produced in the MPEG-4 container format, which uses the .MP4 extension, as well as QuickTime (.MOV), Flash (.F4V), 3GP for mobile phones (.3GP),, and the MPEG transport stream (.ts). Most of the time, but not all the time, H.264 video is encoded with audio compressed with the AAC (Advanced Audio Coding) codec, which is an ISO/IEC standard (MPEG4 Part 3).

H.264 cameras have significant bandwidth savings.

Unfortunately, many factors impact surveillance resolution, far beyond

pixels, such as:

  • Low light performance
  • WDR performance
  • Compression settings
  • Camera angle / down-tilt
  • Lens selection and focus

The latest 4MP cameras offer 2x the pixel count of 1080p cameras. 4MP cameras comes with bad low light performance, even though these cameras overwhelmingly integrated with IR to help compensate.

CCTV Frame Rate

The faster a person moves, the more likely you are to miss an action. You

know the ‘speed’ of frame rate – 1 frame per second, 10 frames per second,

30, etc., but how many frames do you need for reliable capture?

at 1fps, only a single clear head shot is captured, but at 10fps, you

get many more. Finally, at 30fps, you may get one or two more, but it is not

much of an improvement.

Shutter Speed vs Frame Rate

Frame rate does not cause blurring. This is a misconception. The camera’s

automatic shutter speed control does.

1/4000s shutter speed completely eliminates all traces of motion blur, whereas 1/1000 and 1/2000 of a second shutter speeds significantly reduces blur, but it is still noticeable when looking at the recordings frame-by-frame.

On the other side, cameras with slower shutter than the frame rate cause blurring of moving objects, and you lose frames. If you have a 1/4s shutter, the shutter /

exposure only opens and closes 4 times per second. Since this only happens 4 times, you can only have 4 frames in that second.

Average industry frame rate is ~8-15fps, reflecting that this level provides

enough frames to capture most actions granularly while minimizing storage

costs.

CCTV Bandwidth

Bandwidth is one of the most fundamental, complex and overlooked

aspects of video surveillance.

Scene Complexity

parking lot routinely requires 300%+ more bandwidth than the simple

indoor room because there is more activity and more details. Additionally,

scene complexity may change by time of day, season of the year, weather,

and other factors, making it even more difficult to fairly assess.

for example, if a 1MP camera uses 1 Mb/s of bandwidth, a 2MP camera on average might use ~2Mb/s.

Frame rate impacts bandwidth, but for CODECs such as H.264, it is less than linear. So, if you increase frame rate by 10x, the increase in bandwidth is likely to be far less, often only 3 to 5 times more bandwidth.

  • 1 fps: 0.179 Mb/s
  • 10 fps: 0.693 Mb/s
  • 30 fps: 1.299 Mb/s

Compression, has an inverse relationship to bandwidth: the higher the compression, the lower bandwidth will be.

Field of view’s impact on bandwidth varies depending on which width

reveals more complex details of the scene. In scenes with large areas of

moving objects, such as trees or other blowing vegetation, widening the

field of view will likely increase bandwidth. In scenes with relatively low

movement but repetitive backgrounds, such as parking lots, roofing,

patterned carpet or walls, etc., narrowing the field of view will increase

bandwidth due to more of these fine details being discernible.

Sharpness has a huge impact on bandwidth consumption, yet it is rarely

considered during configuration, even by experienced

technicians.

WDR

WDR is the acronym for Wide Dynamic Range. It is a technology that some video cameras have and that serves to compensate for problems with exposure to light. 

Understanding wide dynamic range (WDR) is critical to capturing high quality images in demanding conditions. Cameras need light to generate an

image. However, too much light and the image is washed out yet too little

light and the image is too dark.

An example of the use of this technology is found in the following situation. When a camera is directed towards a window, we can find areas in which more or less light enters. With a normal camera, without WDR, we will see a part of the image very dark and another very bright, with which many details will be lost.

Integrated IR

IR cameras are functioning like normal digital cameras: They have a sighting area, the so-called field of view (FOV), which can typically vary between 6° for a telescopic optic and 48° for a wide-angle optic. Most standard optics are showing a 23° FOV. The farther the object is away, the larger the observed area will be.

Finally, here we see which resolution camera with 15FPS what the bandwidth will be and required storage for 120 days of recording.

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