The Digital Network Camera Surveillance School:

Chapter 4

Recording and storage

It is only recently that Time Laps Video recorders (TLV) based on the VHS-standard were the first choice for recording video images.
   Today, this technology is quickly being replaced by digital hard drives allowing superior capacity and image quality.
   In this chapter of the SecurityWorldHotel Network Video Academy we take a closer look at this aspect of digital network camera surveillance.

Without a great deal of noise or many of us taking notice, our world is becoming more and more digital. Take a quick look around you, so many products today incorporate digital technology – cars, cameras, and microwaves all have integrated digital technology. How has this process of digitisation come about, and how has it affected the security industry?

Recent reports by analyst firms Frost & Sullivan and Joseph Freeman & Co. point to 2002 as the year in which the digital technology surpassed analogue recording in terms of demand. Digital Video Recorders
(DVRs) now constitute up to 75% of all new CCTV systems. The key driver behind this technology shift is the simple fact that digital solutions offer increased performance and improved cost-efficiency. Let’s go into more detail about this.


Leaving old technology behind

The basis in Time Lapse Video (TLV) is traditional VHS tapes that hold up to 540.000 image frames – equivalent to 3 hours of live video. By decreasing images/ hour and distributing the tapes maximal 540.000 images over a longer period of time you can actually record for a much longer time – but at the expense of quality and usability. If you for instance record 72 hours TLV, you only get 2 frames/second.
In a solution consisting of 8 cameras this would mean that there would be 4 seconds between each frame recorded by each camera.


Digital Video recorders – the next step

By replacing the video recorder with a Digital Video Recorder (DVR) you significantly increase the storage capacity without losing quality or usability. For upgrades, this is a very good solution because you can still use your existing analogue cameras. But you still miss out on some of the key benefits of the DVR and the effects of fully utilising the network - and you still have to use dedicated, coaxial cables.

The fact that DVRs can record is self explanatory, but a modern DVR can do much more than that. One interesting feature is the ability to use motion detection, both in live material and in recorded material. Besides the obvious, eliminating the need to record when nothing happens, which saves storage capacity, motion detection also speeds up search for recorded material. Let’s say for example that a box is missing from your warehouse. With a modern DVR you can mark the image where the box stood and then ask the DVR to scan the hard drive and replay the video from the time when there last was activity in that area. In a matter of seconds you will know what happened to the box.


From VCR to IP Surveillance

Surveillance The more end users become familiar with the DVR technology, the more they realise that DVR represents just one more step in the ongoing digital evolution of CCTV systems. Innovation
continues beyond the DVR, and a viable, cost-effective alternative has emerged: IP Surveillance or Networked Video – video transferred over IP infrastructure:

The VCR Era. For quite a while, TLVs (VHS) have been used for recording CCTV images. Digitisation in the CCTV arena was first introduced around 1990 when digital cameras (based on CCD sensors) replaced analogue tube cameras. These CCD cameras were partly digital, but they still used analogue connections and recording was still done on analogue VCR tapes.

The DVR Era. This era can roughly be divided in two. In the first half, around 1996, the DVR’s recording function was next to become digitised (stage 1). This next step into digitisation gave the end user the benefits of no longer having to change tapes, consistent recording quality, and recorded event searches became more efficient. Nevertheless, the DVR still had analogue coax inputs and an analogue output for
the monitor.

The second half of the DVR Era saw a network connection established for the DVR through digitising the monitoring station by employing a PC. In the last two years, DVRs increasingly are increasingly being delivered equipped complete with a network or modem interface so that the recorded images can be monitored remotely, via monitoring software, using a standard PC (stage 2). Newer, more advanced DVRs can use their IP connection not only to communicate with the PC, but also to communicate with other networked cameras.

The IP Surveillance Era. The last stage to complete CCTV digitisation is the link from the cameras to the DVR (stage 3). For many of today’s CCTV systems, this is the last bastion of analogue technology: the coax cable. I Network cameras and Video Servers have hammered the final nail into the analogue coffin by making the link from the camera to the recorder digitised, using standard computer networks, Internet, or even wireless technologies. Furthermore, digital imaging combined with networking enables a whole new range of system-level functionality and cost-efficiency.


Towards Total Digital Functionality

As we’ve seen, the DVR is actually a hybrid technology - part digital, part analogue. Going one step further to a totally digital system makes perfect sense since the CCD (via an A/D converter) already generates a digital image, and the recording on the hard drive in the DVR is also digital. Why perform a digital-to-analogue conversion in the cameras, just to make an analogue-to-digital conversion on the DVR? These multiple conversions slow down performance and increase the cost of the system.

At the most basic level, how do the DVR and IP Surveillance concepts compare?

Let’s examine a single video channel::

With a DVR, the processes of digitisation and compression occur in the recorder unit. But with IP Surveillance most of the “action” moves to the camera, including “intelligent” functions like motion detection and others. Gradually, this more intelligent solution is creating “smart” cameras. IP Surveillance solution sacrifices no functionality; it simply moves it from the DVR to the camera. This explains why the network camera is more expensive initially.


Comparing DVR and IP Surveillance concepts

The DVR and IP Surveillance share a number of beneficial features and functions: recording to
digital hard disk; no tape maintenance; consistent high image quality; fast, easy image retrieval, access to recorded video over IP networks etc. However, a more comprehensive comparison of the two technologies reveals how IP Surveillance technology offers a number of significant advantages over a standard DVR:

• Scalability. IP Surveillance scales from one to thousands of cameras in increments of a single camera. No 16-channel jumps like in the DVR world. Increased frame rate and storage by adding hard drives and PC servers to the network. Any frame rate for any camera at any time is available.

• A more cost efficient infrastructure. Most facilities are already wired with twisted pair infrastructure so no additional wiring, an expensive part of the CCTV installation, is required. Where there is no infrastructure, installation of twisted pair is cheaper than with coax wiring. In addition, wireless networking can be used where cabling is unpractical.

• Systems integration and network convergence. IP Surveillance technology provides an open, easily integrated platform. As system integration becomes increasingly critical, ensure that access control, heating and ventilation, process control, and other systems and applications can be effectively integrated. A single network connects and manages the enterprise for data, video, voice etc.- making management more effective and cost efficient.

• Remote accessibility. Any video stream, live or recorded, can be accessed and controlled from any location in the world over wired or wireless networks.

• Intelligence at camera level. Motion detection, event handling, sensor input, relay output, time and date, and other built-in capabilities allow the camera to make intelligent decisions on when to send alarms, video and at which frame rate, improving information access and decision-making.

• Increased reliability. IP-based data transports enable off-site storage and the ability to use redundant infrastructure, server and storage architecture. By using standard server and network equipment, replacement time if any equipment should go down is considerably less than if using proprietary DVR solutions. Management software provides real-time system health status and information on preventive measures.


IP Surveillance matures

Just as the progressive evolution of CCTV digitisation has yielded improved system performance over time, IP Surveillance promises to continue to deliver a host of attractive, future end user benefits:

• Increased intelligence located at the camera level, such as advanced Video Motion Detection (VMD), license plate recognition, event triggers, object tracking, etc.

• A higher resolution than the limits of the analogue NTSC and PAL formats; up to 0.5 Mpixel. Mega-pixel Network Cameras are already available, and soon they will become multi-megapixel.

• Power via Ethernet – eliminating the need to have power outlets at the camera locations and enabling easier application of uninterrupted power supplies to ensure 24 hours a day, 7 days a week.

• Wireless transmission of video using cost-efficient standard technologies such as IEEE 802.11b, and wireless access to any video via PDAs, Tablet PCs, and cellular phones.

• Encryption, watermarking and connection authentication at camera level, offering a considerably more secure solution than with any analogue camera.


Conclusion

In contrast to common opinion, we have seen that the DVR is a milestone in the continuing development
of the CCTV technology and not just an end point solution. Security started with analogue cameras, switchers and tape recorders; today's recording is digital and since the cameras are also turning digital it is natural to go for a complete digital solution.

The next chapter will cover the different products that can be connected to an IP network.