ELECTRIFIED SECURITY FENCES
CLOSED CIRCUIT TELEVISION
ACCESS CONTROL SYSTEMS
CLOSED CIRCUIT TELEVISION SYSTEMS
ELECTRIFIED SECURITY FENCES
ACCESS CONTROL SYSTEMS
HD CLOSED CIRCUIT TELEVISION SYSTEMS
HD CCTV IMAGERY ON AN ANALOGUE PLATFORM
HD960H Recorders with compatible cameras can provide superb recorded image quality
Because HD960H uses the conventional analogue platform it is backwards compatible with existing cameras so systems can be up-graded in stages or in one go. Images are displayed in the traditional 4:3 aspect ratio up to 1080P with the right monitor. Recorded images can be up up 25% higher resolution than D1 or 4 CIF which was previously the highest available with analogue CCTV.
One of the issues with recording CCTV images is the vast amount of data that has to be stored. More pixels equates to more hard drive space so it is important that any DVR installed has a large enough hard drive capacity to record for the time required without (as has been quite common practice among many installers) compromising recorded picture quality. HD960H does in fact use little more hard drive space than a traditional D1 recorder which previously offered the highest picture quality. However, many D1 recorders are set at CIF to provide sufficient recording time because they were wrongly specified by the installation company.
Although technically not HD, for many applications, HD960H systems provide the best compromise with superb recorded image quality and sufficient recording times without overstretching the budget.
HD IMAGERY CCTV SYSTEMS ARE BECOMING MAINSTREAM
HDSDI CCTV use a 1080P Wide Screen Format, the same as HD Televisions.
Whereas the equipment cost is higher than standard analogue, the introduction of HD-SDI CCTV allows the use of existing RG59 Coaxial Cabling which usually means that system can be more easily upgraded. HDSDI is a Digital Format so unlike HD960H it is not backwards compatible.
In practice, the main benefit is a much clearer picture than traditional standard analogue systems can offer. The wide screen format gives you a larger horizontal and proportionally less vertical viewing area. A wider angle lens can be used to cover a larger area and the zoom facility can be utilised where more detail is required. Care must be taken to ensure that the zoom will be effective and provide usable images where specific parts are of particular interest.
As a rule of thumb, the higher the number of pixels per image, the greater the storage requirement. It follows therefore, that HDSDI DVR’s require a much larger hard drive capacity than their HD960H counterparts. This is often neglected in order to quote a lower price.
Not surprisingly, HDSDI comes at a higher cost than HD960H.
IP Based CCTV SYSTEMS
IP based systems are capable of providing excellent results. Unfortunately, many do not and equipment from different manufacturers is not always compatible. Systems have to be properly designed and specified to ensure sufficient bandwidth to avoid lag etc. The original concept that they could be piggy backed on to an existing network is now virtually forgotten. The need to create a specific network for the system results in their main applications tend to be on larger systems where the budget stands aside for the desire to have the latest and what is perceived as the best.
Cameras up to 10 Megapixels are offered but in practice trying to record such a vast amount of data is problematic and costly. It should also be noted that the use of the HD logo actually restricts how high the pixel count can be so many IP based systems are not technically classed as true HD.
Cameras should be specified to be fit for purpose, provide images to the desired level and the system should be capable of recording for the requisite time.
There are different approaches to achieving HD quality CCTV images. As has always been the case with CCTV, the main stumbling block is with the recordings. Traditionally, the cameras progressed to higher quality before the recordings could catch up.
However, the problem now is one of storage. If you want to store the images from 16 cameras for 30 days with 25 images per second per camera we need to be able to store 25 X 16 X 60 X 60 X 24 X 30 images. This equates to a staggering 1,036,800,000 images! The higher the pixel count (picture quality), the greater the required storage capacity.
Clearly there has to be compromise. One solution that is often put forward is to only record when motion is sensed. Apart from being a grey area where evidence is concerned, it it not very practical outside and restricting the movement to one part of the screen can result in vital images not being recorded.
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CCTV systems have been using the term ‘High Definition’ for a long time. Many earlier systems labelled as such would now be considered to provide poor quality images.
In order to use the HD logo a system must comply with the HD standard. This must be either 1080p or 720p with a frame rate of 25 images per second. No more and no less.
Many recorders which can only record less than a half of the pixel requirements for HD standards have a HDMI output for a monitor which can display HD 1080p. Whereas this might be a small improvement on the images displayed by a conventional monitor it does not have any effect on the recorded images.
Some recorders can record at 1080p or 720p but cannot do so at 25 images per second. Technically, this means they are not recording HD so should not be classed as HD systems.
In practice, 12 images per second is more than sufficient for most CCTV purposes and requires less than half the hard drive capacity for a given recording period.
Currently, sufficient hard drive capacity is a major issue when specifying HD CCTV.
1.3 Megapixel Analogue Cameras?
Analogue Cameras are now coming on to the market with a 1.3 Megapixel Image Sensor.
This it totally misleading as these cameras used with a 960H Recorder will provide the same recordings as a 700 TVL 960H compatible camera of the same quality.