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Video surveillance solution design guide -- part 3: storage of recordings & video analytics
November 08, 2008
By:
John Honovich
This article is part 3 of a four part tutorial series about how to
design a video surveillance solution. It continues by answering
two more of the 7 fundamental questions that need to be
addressed by decision makers. Part 2 of this series
dealt with questions regarding connectivity and the video
management system, while this third part examines the types
of storage used for recordings and video analytics.
4. Storage
Surveillance video is almost always stored for later
retrieval and review. The average storage duration is
between 30 and 90 days. However, a small percentage of
organization store video for much shorter (7 days) or for
much longer (some for a few years).
The two most important drivers for determining storage
duration is the cost of storage and the security threats an
organization faces.
While storage is always getting cheaper, video
surveillance demands huge amount of storage. For comparison,
Google's email service offer about 7 GB/s of free email
storage. This is considered to be an enormous amount for
email. However, a single camera could consume that much
storage in a day. It is fairly common for video surveillance
systems to require multiple TBs of storage even with only a
few dozen cameras. Because storage is such a significant
cost,
numerous techniques exist to optimize the use of storage.
The type of security threats also impact determining
storage duration. For instance, a major threat at banks is
the report of fraudulent investigations. These incidents are
often not reported by affected customers until 60 or 90 days
after the incident. As such, banks have great need for
longer term storage. By contrast, casinos usually know about
issues right away and if a problem is to arise they learn
about it in the same week. Casinos then, very frequently,
use much shorter storage duration (a few weeks is common).
Three fundamental types of storage may be selected:
- Internal storage uses hard drives built inside of a DVR, NVR
or server. Today this is still the most common form of
storage. With hard drives of up to 1 TB common today,
internal storage can provide total storage of 2TB to 4TB.
Internal storage is the cheapest option but tends to be less
reliable and scalable than the other options. Nonetheless,
it is used the most frequently in video surveillance.
- Directly Attached storage is when hard drives are
located outside of the DVR, NVR or server. Storage
appliances such as NAS or SANs are used to manage hard
drives. This usually provides greater scalability,
flexibility and redundancy. However, the cost per TB is
usually more than internal storage. Attached storage is most
often used in large camera count applications.
- Storage Clusters are IP based 'pools' of storage
specialized in storing video from large numbers of cameras.
Multiple DVRs, NVRs or servers can stream video to these
storage clusters. They provide efficient, flexible and
scalable storage for very large camera counts. Storage
clusters are the most important emerging trend in video
surveillance storage. Learn more about
storage clusters for
video surveillance.
5. Video Analytics
Video analytics scan incoming video feeds to (1) optimize
storage or (2) to identify threatening/interesting events.
Storage optimization is the most commonly
used
application of video analytics. In its simplest form, video
analytics examines video feeds to identify changes in
motion. Based on the presence or absence of motion, the
video management system can decide not to store video or
store video at a lower frame rate or resolution. Because
surveillance video captures long periods of inactivity (like
hallways and staircases, buildings when they are closed,
etc.), using motion analytics can reduce storage consumption
by 60% - 80% relative to continuously recording.
Using video analytics to identify threatening/interesting
events is the more 'exciting' form of video analytics.
Indeed, generally when industry people talk of video
analytics, this is their intended reference. Common examples
of this are perimeter violation, abandoned object, people
counting and
license plate recognition. The goal of these
types of video analytics is to pro-actively identify
security incidents and to stop them in progress (e.g.,
perimeter violation spots a thief jumping your fence so that
you can stop them in real time, license plate recognition
identifies a vehicle belonging to a wanted criminal so you
can apprehend him).
These video analytics have been generally viewed as a
disappointment. While many observers believe that video
analytics will improve, the video analytics market is
currently contracting (in response to its issues and the
recession). Learn more about
the challenges in video
analytics.
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About the Author
John Honovich is the Founder of IP Video Market Info. You
may hire John or other industry experts in the
IP Video Marketplace.
Also See:
[
Designing video surveillance solutions: intro & camera selection ]
[
Camera connectivity & types of video management systems ]
[ How
to view surveillance video & integrating with other systems ]
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