Defining Technology

Understanding and evaluating new DVR technologies

• By Cynthia Freschi
• Sep 21, 2007

WHEN evaluating digital platforms, there are many factors that need to be considered. Understanding real-time recording versus time-lapse recording, defining resolution, calculating storage and more can all prove to be an ongoing challenge for most.

The objective of security management is to capture as much quality information as possible using the least amount of recording media. This holds true in digital, as well. From the beginning of CCTV in security applications, the standard of measuring real time for all moving images was defined at 30 frames or 60 fields per second.

Setting the Terms
In today’s security world, acronyms are a favored form of communication. Unfortunately, different manufacturers use different terminology. For example, with regard to how much information will be recorded, people will most often find references to ips (images per second) and fps (frames per second or fields per second). The question you need to ask is if fps stands for “frames per second” or “fields per second.” Or does ips equate to field or frames? Thirty frames per second is equal to 60 fields or images per second, which is true real-time NTSC video. Some manufacturers record at 30 ips, while others record at 60 ips. Although this seems confusing at first, there are specific differences between the two that should be clarified during the selection process.

One also must consider the compression technology the manufacturer is using. For example, H.263, Wavelet, MPEG-2, MPEG-4, JPEG and MJPEG are a few compression modes you will most often see—each of which offers specific benefits, as well as sacrifices. The selection of compression technology for a system’s needs can vary greatly.

Compression affects both bandwidth and resolution. Some compression methods or hybrid versions are better at passing high-quality images at lower bit rates, while others are better suited for streaming live video over LANs or WANs. It is somewhat disputed as to which technology is better suited for recording digital video in security applications. However, determining the most important factor at a facility will help decide the most appropriate compression technology needed.

A Resolution Revolution
Most of the accepted enterprise-level DVR solutions use MPEG-2 or MPEG-4 compression and portray resolution as common intermediate format (CIF) or source input format (SIF). A variation of CIF or SIF seems to be the most regularly used. CIF/SIF images are 352 pixels wide and 240 pixels tall. QCIF is one-quarter CIF and usually considered too low a resolution for security applications. CIF is a slightly better resolution than a VCR produces and, in most cases, adequate for back-of-house operations and parking. Four CIF uses 704 or 640 x 480 pixel resolution, roughly four times the area of CIF, and this loosely equates to DVD-quality video. This will produce the highest quality images available in today’s marketplace.

D1 produces 720 x 480 for NTSC, and for product evaluation purposes, is comparable to 4 CIF. Two CIF varies from product to product but is usually 640 x 240 pixels, although it has recently been defined as 340 x 480.

Recommendations are generally no less than 2 CIF at 30 frames per second for all high-priority areas. Commissions across the country have started writing regulations for resolution, along with other factors of digital. Some suggest checking with the governing agency to find out if there are regulations to record at a certain resolution and speed.

Size It Up
Dealing with space is always an obstacle. Establishing the system’s footprint should be considered prior to making a decision. Flexibility in digital-based systems design is important to determine how to keep an eye on space without sacrificing serviceability. New properties and retrofits should incorporate IDF, TR or other conditioned closets into the design plan. With the use of Cat 5, UTP and Ethernet technology, encoders and network hubs can be co-located throughout a property with only a network connection back to the equipment head-end room. This enables a casino to take full advantage of the systems’ architecture while saving some much-needed space.

This plan only works when using an IP or encoder-based system and is not designed for an “all in one box” solution. Keep in mind that if the user is going more than 300 feet on any Ethernet connection fiber must be used.

Storage can also be a problem. Storage calculations, unfortunately, are not the exact science they should be. When calculating storage, calculate it at 100-percent motion for budget purposes. Manufacturers try to stay competitive, and storage is the most expensive part of the system. Experts have tried to estimate the motion in a casino to determine adequate storage, but have yet to be successful.

When issuing a request for proposal, be sure to include how many days the video will be retained. For example, “System to record 512 cameras at 4 CIF RAID5 for no less than seven days.” Buy the system per your parameters. Forget how many Terabytes are being considered for purchase. Make sure the contract or proposal clearly spells out the desired storage retention, should it be under-specified.

Although DVRs have come down drastically in price, digital recording is still quite an expensive investment. Be sure to choose a qualified systems integrator who is teamed with a reputable manufacturer. Request demonstrations, then ask to demo the product onsite for a week or two. Ask as many questions as possible, and be sure you are comfortable with the company that will install the system, as you will most likely be dealing with that company for a while.