Since 9-11, security has taken on increased importance for businesses and government agencies across the world, and has increased their reliance on sophisticated and comprehensive surveillance systems. Surveillance equipment manufacturers have responded with system improvements, including the use of digital video recording devices that employ hard drive storage developed specifically for surveillance and security. This article discusses why hard drives have become so important in global surveillance. It explains how drives that are engineered and optimized for video surveillance differ from traditional desktop- or consumer electronics-purposed drives, and how they can enable security systems to capture, store, recover and even manage video data. Basic guidelines to help manufacturers select and integrate drives suited to their industry’s surveillance requirement will also be introduced.
By Mark Wojtasiak
In recent years, businesses and government organizations have dramatically increased their reliance on sophisticated, digital video surveillance systems -- and with good reason. Security issues weigh on everyone’s mind in the post-9/11 era, and more advanced, efficient and effective surveillance can help address those concerns.
Digital video technology can deliver a level of sophistication not available from analog systems and meet the ever-growing demand for better security. Statistics confirm the increasing market requirements for digital video: According to J.P. Freeman Co., the estimated worldwide market for all types of video surveillance equipment is US$4.5B at the factory level with a Compound Average Growth Rate (CAGR) of 18%. When the analog portion of the market is removed and digital systems only are considered, the market growth rate nearly doubles to approximately 42% (CAGR) (source: J.P. Freeman Co. “2006 Worldwide Video Surveillance Market Report,” March 1, 2006).
What are the advantages of digital- versus analog-based video surveillance solutions, and what should manufacturers consider when selecting key components, like hard disk drives, for a digitally-based system?
WHY ANALOG NO LONGER CUTS IT
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Figure 1. Video Tape Vs. Disk Drive: Accessing a Desired Piece of Video Data (Source: Seagate Technology)
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Much like the home VCR market was in the 1980s and 1990s, the video surveillance market has been dominated by traditional tape-based systems that use analog technology to capture and record surveillance footage. And just as the home video market quickly replaced VHS tapes with digital DVDs to enjoy superior image quality and reliability, the video surveillance market is now eschewing tape-based solutions in favor of digital systems. The liabilities of analog technology tape-based systems, discussed below, are numerous, interrelated and rapidly prompting surveillance solution manufacturers to “go digital.”
·Recording Time: This is a function of both tape speed and tape length. Decreasing the tape speed increases the maximum recording time per cartridge, but image quality can be significantly degraded. Increasing the tape length allows more recording time but requires thinner tape in order to fit in a standard cartridge; thinner tape is more fragile, increasing the chance of tape stretching or outright breakage.
·Recording Quality: This is primarily a function of tape speed. Faster tape speed yields higher image quality but cuts the maximum recording time per cartridge, thus requiring users to more frequently load and unload tapes throughout the day. Using thinner tape boosts maximum recording time but, as noted above, increases the chance of stretching and degrades image quality.
·Multiplexing: Multiple video streams can be sent to a single recording device via the use of a multiplexer. However, tape-based storage entails compromise because a single cartridge cannot simultaneously meet the needs of high-resolution streams (ideally recorded at higher tape speeds for maximum image quality) and low-resolution streams (preferably recorded at low tape speeds for maximum recording time).
·Accessibility: Tape-based surveillance storage can only sequentially access a desired piece of video data. That is, a search that begins at point A on a tape and ends at point B (where the desired video footage resides) must traverse all of the data in between those two points. This greatly slows down access, particularly when the start/stop points are at opposite ends of the tape. Furthermore, once found, the desired footage can suffer degraded image quality from repeated reviewing. Because the tape is in actual physical contact with the tape head, frequently playing and rewinding the tape can gradually wear away the magnetic coating that stores the video data. Image degradation can also occur during storage due to print-through, wherein magnetism from adjacent tape layers bleeds through to imprint ghost images.
THE DIGITAL ADVANTAGE
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Figure 2. Offering up to 750GB capacity per disk drive, surveillance storage systems equipped with HDDs provide freedom to employ a multitude of cameras for broad, comprehensive video surveillance coverage.
(Source: Seagate Technology) |
When compared to legacy tape-based systems, digital video surveillance technology offers dramatic operational advances in quantity -- the volume of video streams a surveillance system can capture and store; quality the image quality of video data, expressed in terms of frames per second (fps) and frame resolution (for example, 720 x 480 pixels); and accessibility how quickly stored video data can be retrieved and reviewed. These advantages stem in large part from the use of Hard Disk Drive (HDD) storage as part of the surveillance system. HDDs bring unprecedented power to security applications by enabling a comprehensive range of benefits and capabilities, including:
·Huge Recording Capacity: Offering up to 750GB capacity per disk drive, surveillance storage systems equipped with HDDs provide freedom to employ a multitude of cameras for broad, comprehensive video surveillance coverage. Dozens, even hundreds, of video streams can be accommodated simultaneously, all without the need to periodically remove and insert tape media. Furthermore, this wealth of capacity pays important dividends in the ability to archive video for extended periods. Archive periods can be economically extended from thirty or sixty days to months (even years), providing additional security protection as well as ensuring compliance with rigorous regulatory and legal requirements.
·Superior Image Quality: HDD storage ensures consistently superior image quality by eliminating poor signal-to-noise ratio, saturation, tape stretch, and other analog limitations that undermine recording quality. HDD storage also does away with tape’s trade-off between recording speed/quality and recording time/capacity, and enables multiplexed streams to be individually configured for optimum results. Even more importantly, the enormous capacity of disk-based storage lets users specify more aggressive capture rates and resolution (for example, 30 fps and 740 x 480 pixels) to maximize image quality. Such settings can rapidly consume vast quantities of storage space, which an HDD based system can readily supply. As a result, image quality need never be compromised because of limited storage capacity, a key consideration with forthcoming intelligent video applications.
·Rapid Accessibility: Disk-based surveillance storage offers random access to any video data on the disk drive. This means that the read/write head can go directly to the desired video footage, bypassing all of the data that lie between the search’s starting point and its destination. The random access supported by HDDs is dramatically faster than sequential access offered by tape-based storage; furthermore, with no tapes to swap in and out, the surveillance system’s disk drives (and the video images they contain) are always immediately available. And because the disk drive’s read/write head does not physically contact the platter, video footage can be reviewed again and again without image degradation.
LOOKING AHEAD: HDDS AND INTELLIGENT VIDEO
The value proposition of digital surveillance systems equipped with hard disk drives becomes even more compelling when intelligent video applications are added to the picture. Taking full advantage of the high-resolution, capacity-intensive video streams that HDD storage effortlessly handles, intelligent video applications will profoundly increase both the capabilities and cost-effectiveness of video surveillance systems.
At its core, intelligent video reviews the exceptional detail found in high-resolution video streams and analyzes it to recognize visual patterns. Perhaps the best-known use of this technology is facial recognition; intelligent software analyzes the faces of persons in stored surveillance footage, comparing their features to the faces of known suspects or criminals on file. When a match is identified, the application automatically notifies security personnel for follow-up investigation.
Of course, these applications review stored surveillance footage (review being too calculation-intensive for real-time processing) for other visual patterns as well. For example, the application can be configured to identify unusual behavior (such as a person running in an area where such activity is unusual), flag suspicious persons and alert security staff. Or it can compare reference video images of a locked door to surveillance footage to check for signs of a break-in.
The remarkable synergy between intelligent video applications and digital video surveillance systems makes the benefits of disk-based surveillance storage even more compelling. That said, all disk-based storage is not the same. Surveillance has unique requirements that demand drives specifically engineered to meet those needs.
SURVEILLANCE-PURPOSED HDDS: HOW AND WHY
Hard disk drives specifically engineered and optimized for digital video recording in security and surveillance go beyond the capabilities of standard hard drives and deliver real advantages. Surveillance drives not only offer increased capacity; they also provide features that intelligently deal with heat management and power consumption challenges inherent in always-on surveillance environments.
Surveillance-purposed drives are relatively new to the market and many manufacturers do not have experience with selection or integration. Here are a few key points and features that manufacturers should consider when choosing a security-purposed HDD:
·Capacity: As one would expect, capacity is a key consideration in selecting a drive purpose-built for surveillance. Drives available today can store up to 750GB, a capacity level that will support 217 continuous days per camera (at 640 x 480, 1 fps) or 24 continuous days per camera (at 720 x 480, 30 fps) while recording 24 hours a day, 7 days a week. Applications requiring lower-level capacities can choose surveillance-purposed drives at capacity levels beginning at 320GB.
·Advanced Power Management Features: Surveillance-purposed drives should require lower startup current, enabling the design of low-cost power supplies. The drives should also include the capability to power down when not in use, saving power and enabling more efficient system cooling.
·Intelligent Workload Monitoring: Surveillance-purposed drives should utilize monitoring algorithms to sense specific workload profiles that can stress key systems and then take corrective action.
·Designed for 24x7 Operations: Drives purposed for surveillance should be able to withstand the intense duty cycles common in digital video recording for security and surveillance.
Video security drives are primarily used for streaming video, but they must also be capable of conventional data reads and writes that are used in the course of managing video databases and related applications.
In response to users’s heightened security concerns and needs for more powerful, cost-effective solutions, manufacturers can expect that demand for analog-based tape systems will give way to more widespread adoption of digital surveillance systems. When developing digital solutions, manufacturers should carefully consider their choice of Hard Disk Drive (HDD) storage, an integrally important component in these systems.
In the near term, surveillance-purposed HDDs, which deliver an unprecedented combination of capacity, speed and durability, will enable a compelling new class of surveillance applications.
In the longer term, surveillance-purposed HDDs will drive development of intelligent video, delivering dramatic advances in surveillance systems capabilities and cost-effectiveness. With its myriad benefits and flexibility, digital video surveillance using HDD storage is here to stay.
Mark Wojtasiak is Senior Segment Marketing Manager of Video Applications at Seagate Technology (www.seagate.com).
For more information, please send your e-mails to swm@infothe.com.
ⓒ2007 www.SecurityWorldMag.com. All rights reserved.
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