Technology

Dr. Wallace Ma – Executive Committee Member, Hong Kong Security Association

Improvement on video clarity is always a common goal in the video surveillance industry. Resolution of analog video surveillance cameras have been increased from 400 to 500, 600 and even 700 TV lines in the past few decades. Nevertheless the room for further improvement is getting smaller and smaller due to the technical limitation of the composite video standard. Hence the industry is adopting a new video standard so as to further improve the clarity of video.

TV broadcasting industry has been evolving from analog to digital and now the high definition (HDTV) era. Everyone can reveal there is a dramatic improvement on video clarity in comparing HD versus analog video programs. We firmly believe video surveillance industry will naturally follow the same technology trend.

Apart from the benefit of video clarity, HD video also comes with 16:9 aspect ratio in contrast with 4:3 of conventional analog video. In other words, HD video would give 33% wider viewing area than analog video, provided that same objects occupy the same percentage of vertical view on both screens.

Last but not the least, the transmission of HD video is purely in digital format. It would facilitate much higher noise immunity in comparing to analog video. Hence the quality of HD video would be more consistent and less variant to the cable network.

Nowadays HD video supports 720p (1280×720 pixels) and 1080i/p (1920×1080 pixels) resolution standards, versus DVD video is digitized in 720×576 pixels. The resolution of HD video is 2 to 5 times of the digitized analog video. Owing to the substantial increase in video resolution, the efficiency of the compression engine plays an extremely important role in determining the performance of HD video surveillance systems. On the other hand, video recording and video streaming over communication networks are equally important in today’s requirements of a professional video surveillance system. Hence compression engine supporting to generate a dedicated recording stream would be utmost important as no user would like to compromise the recording performance while video streaming is taken place at the same time.

Additionally when we look at the detailed technical specifications of HD cameras, we would find that some models would produce HD resolution video only on their main stream, whilst the auxiliary stream(s) would only be in CIF resolution (352×288 pixels) or D1 (720×576 pixels) the highest. If this is the case, the video surveillance system would not support monitoring in HD resolution when it is configured to record in HD resolution or the frame refreshing rate would be decreased. Certainly it should be a vital considering factor when choosing a HD video surveillance system. Also it gives a reason on the price difference of HD cameras in the marketplace..

Video streaming over the Internet is becoming today’s a very common requirement in video surveillance systems. Nevertheless news of IP cameras and video surveillance successfully attacked by hackers and video footages exposed to the public has been reported from time to time. In fact there are a lot of videos in YouTube demonstrating how IP cameras from different manufacturers could be attacked.

Hence the security feature is definitely a very important consideration when choosing a video surveillance system. How secure is it in the authentication process? What video streaming protocol is being used? What sort of encryption process, if any, is in place? Would all these provide adequate protection against hacker attack.

Apart from equipment, system administrators also play a vital role to ensure the security of the video surveillance systems. It is utmost important to ensure all the security features of the video surveillance systems are properly configured and deployed. Otherwise it would not help regardless how good the security feature of the video surveillance system is designed.

Many users would ask for open platform approach for their HD video surveillance systems at the first glance. Undoubtedly open platform design would have the freedom in choosing HD cameras from different manufacturers. However is it the only requirement in selecting a video surveillance system?

In order to support cameras from multiple manufacturers, an open platform design usually employs standard protocols available in the industry, in which many of those are not primarily designed for video surveillance applications. Owing to the “openness” of these standard protocols in nature, the security level of these standard protocols is limited.

As the open platform approach tries to standardize the communication format of products from different vendors. At the same time, it would inevitably standardize the features and performances of these products. Many manufacturers develop innovative and unique features that would benefit users in their applications. Nevertheless these features would be forced to disable when the cameras are being used in an open platform. For instance, even though some manufacturers have developed a better compression technology delivering better video quality and generating less data traffic on the network, it cannot benefit users in an open platform as nowadays most of them only support the standard compression technologies.

Traditional video surveillance systems are primarily designed for evidence collection. Users would replay the video footage from their digital video recorders and try to find out how incidents happened in the past.

BS8418 is a code of practice for the design, installation, commissioning, operation, maintenance and monitoring of detector-activated video surveillance systems. The primary objective of BS8418 is to minimize the number of false alarms requiring the UK Police to attend. Compliance to BS8418 is certainly not a requirement for video surveillance systems in Hong Kong and anywhere else outside the UK. Nevertheless it gives us a good idea on how we can deploy a video surveillance system for detecting any abnormal and illegal activities and alerting users to take swift and appropriate actions so as to deter these activities and minimize their damages to the user’s property.

Nowadays IP network is the most commonly used approach for connecting HD video cameras to the video recording and management devices. Nevertheless some video surveillance system manufacturers have commenced offering SDI (synchronized digital interface)-based HD video surveillance systems into the marketplace.

Both IP and SDI cameras output videos in the form of digital data. However they use completely different approaches in the cabling topology. IP cameras literally can run on any IP network through CAT5 or CAT6 cables. Multiple IP cameras can be connected in one common network and they are distinguished by their unique IP addresses. In order to achieve the optimal performance, it is necessarily to take the network traffic, load balancing into consideration when designing the network configuration.

On the contrary, SDI cameras run video data through separate 75Ω coax cables back to their digital video recorders (DVR). The networking topology is very similar to the one we have been using for analog camera systems. This is the reason why there is an impression, in which users can upgrade their existing analog to HD video surveillance system by just by replacing their analog cameras and DVRs to HD SDI models and keep using the existing cables.

Although both analog and SDI cameras run videos on 75Ω coax cable network, the bandwidth requirement of HD SDI cameras is much higher than that of analog cameras. In other words, the 75Ω coax cable network working perfectly for analog videos does not necessarily mean it would perform in the same way for HD SDI videos.

Technically speaking RG59 coax cable works very well for analog videos in many applications; whilst it can only work for HD SDI videos with quite short cable length. We would normally recommend using RG6 coax cable for proper HD SDI video surveillance system installation.

In conclusion, both IP and SDI have their pros and cons for using in HD video surveillance systems. It is the most important to understand their characteristics and select the better approach according to the user’s requirements and the nature of the premises.

High definition (HD) video is definitely a major trend of development in the video surveillance industry. I hope the article can shed light on the common consideration factors in choosing a HD video surveillance system. Certainly there are also other considerations specific to different site’s conditions and user’s requirements.