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What to look for in CCTV Cameras

The need for CCTV cameras has escalated in recent years. Today you will find both business organizations and home owners to be incorporating the use of CCTV cameras for the purpose of security surveillance.

The increase in demand has given birth to a full fledge industry of CCTV manufacturers. Due to the increased competition CCTV cameras have now become quite affordable for the masses.

Price alone does not make a CCTV worth buying. There are a number of other aspects that you need to take into consideration when going choosing a CCTV camera. Some of the things to look out for are as follows:

Things to look for in CCTV cameras

One of the things you should look out for is the number of frames per second that your Digital Video Recorder has the capability to offer. Thirty frames per second is the standard for a real time video. Anything that falls short of this standard will not be able to deliver you the kind of video quality that you require. Hence you need to go for a CCTV camera that offers you 30 frames per second as a minimum. Today you will be able to find DVR cameras that are capable of recording up to 120 frames per second.

Another very crucial aspect that needs to be checked when choosing a particular CCTV camera is the TV lines that are supported by the device. TVL refers to the horizontal lines produced by the camera and the higher they are the better picture quality the camera will be able to offer. You will be able to find CCTV cameras with 400TVL as the standard. The latest cameras can give you up to 480TVL. There is one thing you need to keep in mind though and that is the fact that the higher the TV lines the more expensive your camera is bound to be. But then again it will be that much better when it comes to the clarity of the picture.

The resolution of the camera is also something that needs to be taken into consideration when going for a CCTV camera. You need to see the original dimensions of the camera in pixels. The higher the resolution the better quality picture your CCTV camera will be able to produce.

You also need to take into account the HDD capacity of the camera that you go for. This refers to the memory bank of recorded data on the DVR. Every camera has a certain time period after which it will recycle the recorded data. The best of CCTV cameras come with motion sensors. This means that they only start recording when they sense some motion. This does not mean there will be no image. On the contrary the image will be there but it won't be recording until there is some change in the environment. The higher the memory the longer your camera will be able to store the recorded data.

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What You See Is What You Get

Why are the images during a CCTV playback so different from images during live view? That is a common question raised particularly when you are trying to identify the suspect from the recorded video. The sad truth is, in most cases, it's not - particularly in the playback mode.

DVR Video Capture Card

DVR stands for Digital Video Recorder and what it comprises is a black box that take in analog video signal from cameras, convert and digitized that signal for storage on the hard disk.

In order to record and hence playback good quality image, we need to start with ensuring that we have a reasonable camera capturing images under adequate lighting.

Recording Frame Rate

Once that is taken care with, we must then consider the quality of the DVR's video capture card. The Video Capture Card performs the conversion of analog to digital and is often specified in terms of its frame rate, the image resolution and the compression method.

To digitize the video, the Video Capture Card takes the analog video, and broke it into different frames, digitizing one frame at a time. Hence a Video Capture Card that is specified 25 frames per second (fps) can process at the most 25 frames per second. If this card is connected to 4 cameras, the maximum frame rate per camera will be 6.25 fps. This frame rate will affect the quality of the playback.

Display Frame Rate

A different circuitry (either on the same video capture card or on the mother board) is used to display the video signal to the monitor. The quality of the display is, like video capture, measured by its frame rate. The recording and the display frame rate need not be the same. In fact, more often than no, the display frame rate is higher than the recording frame. Which is why the images appears better when view live,

Video Compression

To save on hard disk space, the data after conversion is compressed. With compression, certain image details such as sharpness or richness of color will be affected, resulting in a difference between what you see live and what you see at playback.

Viewing over Network and Internet

Depending on the DVR, there may be a marked difference between the playback images at location versus viewing them over the network and the internet.

Streaming over the internet or network is heavily dependent on the traffic and bandwidth. Hence, to ensure that they can still deliver images even over the internet, some DVR employs a higher compression ratio. Meaning the data is packed even smaller so that it can get down the internet to your computer, resulting in poorer images than what was viewed at location.

Will things get getter?

The world is moving towards greater digitization, resulting in better data compression algorithm being developed and tested. The DVR since its inception has gone through tremendous changes, and what we are seeing is the development of better algorithm that is packing the video data smaller, with better resolution.

The future is bright, and yes, the image should be better, brighter and sharper with the newer range of DVR

How Big is Your Hard Disk

Digital Video Recorder (DVR) is fast replacing VCR. Utilizing hard disks instead of video tapes, images from security cameras are digitized and stored. Retrieval is fast and time saving as you can specify particular date and time. But how big should the hard disk be?

Understand your requirement

To determine the required size, we need to ask the following questions:

how many cameras do you have
what is your require image resolution
how smooth the movement determined by frame rate
how long do you need to keep the records before it can be overwritten
what compression algorithm is used

Your answers will affect our computation.

How many cameras

Images collected by each camera is individually digitized and stored. Hence, the more cameras you have, the more images will be generated, the bigger the hard disk required. Typical DVR supports 4, 8 or 16 cameras.

Image Resolution

Like a digital camera, you can select the resolution of the image recorded. Depending on the DVR, the image file size can vary from 10KB to 25 KB. The bigger the file size, the higher its resolution.

Frame Rate

Digitization involves breaking the video stream into frames and capturing each frame. Frame rate, normally depicted as frame per second (fps) is the number of frames captured per second. Typical range is 1, 2, 3, 6, 12, 25 frames per second. A DVR that is set at 1 fps means that only 1 picture will be recorded in a second, resulting in jerky movement. Typical setting for surveillance ranges from 3 to 6 fps.

How Long before Overwritten

How long does it take before you discover an incident or an irregularity? That time lapse is often a good guide to how long you need to keep the record for. Idealistically we may like to keep the data forever, but that is a practical impossibility. Hence we need to consider how much time will lapse before we discover an incident. For example, retail cashiers close the accounts everyday and if there were any shortfall, it will show up by end of business day. Any investigation can be conducted and completed within 3 days, making a week long enough.

What compression method

Depending on the compression algorithm, the size of video can differ. Common compression methods used by DVR are MJPEG and MPEG.

So how big the hard disk

Assuming that you have 4 cameras recording at normal resolution (say 10 KB) at 3 fps, the hard disk spaced used to record for 1 second would be 4 x 10 x 3 = 120 KB.

If you are to record continuously for 24 hours and would like to keep the data for a month, the total hard disk space used would be 30 (days) x 24 (hr) x 60 (min) x 60 (sec) x 120 KB = 311,040 KB, approximately 300 MB.

This is a simplistic calculation as it does not take into consideration the effect of data compression. With compression, the requirement would be lower than the 300 MB. Hence the 300 MB represent a higher but reasonable estimate.